Low bb height and pedal strikes.- Mtbr.com
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  1. #1
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    Low bb height and pedal strikes.

    I've had a few modern frames lately and, although I love 425mm chainstays, a bit more travel and slacker head angles, it all goes in the toilet when I have ridiculous pedal strikes. One hardtail frame I really wanted to love in particular, even with 170mm cranks was catching roots and small rocks all the time!

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    One riders low BB is apparently another's handling dream. I find bikes with too low of a BB to be dangerous. It isn't that I can't time, ratchet, and turn as needed to avoid serious strikes. I can. It is that once in a great while I just screw up and have a massive strike that causes a crash. At first I thought it was a random event, and it some ways it is. But it happens only on my bikes with what I consider to be an excessively low BB. After a concussion where I only remembered the actual strike two weeks later, granted the mangled pedal was a bit of an immediate clue, I decided to get a bit more serious about the problem.

    I now have two bikes with 165mm cranks which has ended the surprises. Full squish bikes are a bit more of a challenge because determining where the BB is at is a moving target. Part of that moving target is more dependent on suspension kinematics. Despite a tendency to stay high in the travel, starting at "barely adequate for a hard tail" isn't really a great place to start.

    I'm experimenting with a crown race spacer, but like everything else I'm sure it will come with compromises.

  3. #3
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    It's not black or white. You can get pedal strikes with any reasonable height BB. A little lower and you can get a few more pedal strikes. No matter the BB height, pedal strikes are avoided by phasing the cranks properly and ratcheting as needed. It's more a matter of awareness and skill than BB height.
    Do the math.

  4. #4
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    The new long/low geometry of bikes the last couple years lends itself to more pedal strikes, but the benefits of handling far outweigh the occasional strike. After a couple months I learned to anticipate where and when they might occur and adjust my pedal position accordingly. I rarely have an issue now.

  5. #5
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    Some have taken it too far. Although a few pedal strikes while climbing may be a bit annoying, it's downright dangerous when you are low on energy or tied, cruising at a decent speed, and you clip your pedal/crank on something because you let your pedal/arm hang too low. Those crashes hurt and break stuff.
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  6. #6
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    Quote Originally Posted by adaycj View Post
    One riders low BB is apparently another's handling dream. I find bikes with too low of a BB to be dangerous. It isn't that I can't time, ratchet, and turn as needed to avoid serious strikes. I can. It is that once in a great while I just screw up and have a massive strike that causes a crash. At first I thought it was a random event, and it some ways it is. But it happens only on my bikes with what I consider to be an excessively low BB. After a concussion where I only remembered the actual strike two weeks later, granted the mangled pedal was a bit of an immediate clue, I decided to get a bit more serious about the problem.

    I now have two bikes with 165mm cranks which has ended the surprises. Full squish bikes are a bit more of a challenge because determining where the BB is at is a moving target. Part of that moving target is more dependent on suspension kinematics. Despite a tendency to stay high in the travel, starting at "barely adequate for a hard tail" isn't really a great place to start.

    I'm experimenting with a crown race spacer, but like everything else I'm sure it will come with compromises.
    Most pedal strikes are merely an annoyance, but I agree they can sometimes be dangerous. I have to be especially careful when I'm tired. My worst strike happened on an exposed decent on the Black Canyon Trail. I was in the last four miles of an all day ride and not paying attention to my pedal position. I went down hard, thankfully on one of the few sections of trail where that didn't mean launching off a cliff into rock and cacti. The pedal was fine (RF Chester), but I cracked the bottom bracket shell of my carbon Fuel EX.
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  7. #7
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    I hate low BBs.
    This one trail, its not hard as far as rocks/roots. Not at all.

    But, its all off camber, and narrow.

    My Remedy, I had a total of 4 very light and gentle pedal touches in the entire 10 mile loop.
    My one other bike, I had over 25 in the first 1.5 miles. Some were very strong impacts. Just pedaling around caused the impacts as the crank kept smacking the upside of the off camber hill.
    That bikes BB is WAY too low, and its the lowest BB of all of my bikes, and all of the bikes of my entire family.

    Low BB height and east coast are stupid.

  8. #8
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    Quote Originally Posted by Xlr8n View Post
    The new long/low geometry of bikes the last couple years lends itself to more pedal strikes, but the benefits of handling far outweigh the occasional strike. After a couple months I learned to anticipate where and when they might occur and adjust my pedal position accordingly. I rarely have an issue now.
    Same. Learned to be more aware ratchet ect.

    I wouldn't trade it though that low center of gravity has changed my riding.

    If all your doing is rock crawling then a higher bb might work for you.

    My last bike was a Recluse and it has a highish bb and short stays. I never got used to it or entirely comfortable.


    Edit just measured my bb height and it's right around 340mm on a 130mm travel bike. Now my bike is built up on this frame https://www.lightcarbon.com/all-new-...s958_p118.html

    So my center of gravity is low just based on suspension design and where the weight is (low).

    I'm running 170 cranks and me03 ht magnesium pedals. Which are very thin.

    So what is low?

  9. #9
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    Alright if you like coasting downhills or pedal like mad on smooth trails without rocks and roots.

    Bloody awful if you like climbing and hammering down rocky and rooty stuff.

    I've found it dangerous.

    Some will say "ratchet and time your pedalling". Which is kind of hard when you're busting a gut to get up a rocky trail with rocks everywhere...lose momentum and you're done for.

    It's a shame that these FS bikes with all their traction can get gazumped by simple pedal strikes.

    It's like having a 4x4 as low as a street car.

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  10. #10
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    No free lunch! Low BB gives freaking awesome handling, cornering, etc. on reasonably smooth trails. Higher BB gives awesome pedaling on really chunky pedaling and/or climbing trails.

    You just have to find the compromise BB height that works for you and your main riding area. For me, ~335 on my 115 bike and ~340 on my 130 mm bike works well. Sometimes, I wish for lower when I'm blasting down a flow trail, and sometimes I wish for a bit higher on a long day of chunky pedaling.

    Rear suspension support matters, too. Sometimes just inserting a slightly larger volume reducer in the shock makes a noticeable difference with pedal strikes. The worst bike I ever had in this regard was an old, old Epic. Low BB, locked out until it wasn't, then once the brain opened, it was kinda like a trap door opening -- bam, down to the bottom! Not a great feature at the end of an exhausting endurance race.
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  11. #11
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    Quote Originally Posted by Mr. Blue Sky View Post
    I've had a few modern frames lately and, although I love 425mm chainstays, a bit more travel and slacker head angles, it all goes in the toilet when I have ridiculous pedal strikes. One hardtail frame I really wanted to love in particular, even with 170mm cranks was catching roots and small rocks all the time!
    My 2016 Stumpjumper FSR (29x2.3) AND my 2019 Chameleon (27.5x2.8) has higher BB height than my year 2000 26" Stumpjumper hard tail.

    I struggle over the idea of today's bikes having low BB height. It's a continual comment but I have yet to have somebody post the actual height of their new bike relative to their previous bike.

    I'm not saying it isn't true. It's just that I have not personally seen a spec indicating a lower height than they used to be on small bikes.

  12. #12
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    Quote Originally Posted by adaycj View Post
    I now have two bikes with 165mm cranks which has ended the surprises.
    Smart. Ride chunky and/or extended, rocky off-camber trails with a low BB and you will have pedal strikes. Especially on a SS when powering through uphill rock gardens. Regardless of how awesome your phasing/ratcheting skills are.

    Iíve got a 34Ē inseam and over the last year have switched both of my MTBs (rigid SS) and my SSCX to 170mm cranks. Huge improvement and no way Iíll go back to the 175s (and 180s) of yesteryear

  13. #13
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    In july i went from 175 to 165 for a few $, great results, just do it.

  14. #14
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    BB height really should be based on application (not simply good or bad). If you never ride high speed descents and stick to typical XC trails there's not a big benefit to a low BB. The benefits come on the downhills, especially at speed (i.e. enduro racing, DH, bike park) by improving stability. Personally, I've never had a significant pedal strike while I wasn't pedaling and don't consider a low BB an issue when coasting.

  15. #15
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    Quote Originally Posted by jeremy3220 View Post
    The benefits come on the downhills, especially at speed
    Oh yeah.

    Low bb height and pedal strikes.-img_5387.jpg

    To be fair to the cranks, they only failed after years of DH and enduro, enduring many hits.
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  16. #16
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    So Iím calling BS on the improved handling that comes from a reduction in BB height of 5-10mm. Seriously, no one but a pro could tell the difference, itís just not enough especially when you consider all the other variables like seat and bar height, crank length, shoe/pedal thickness, even tire pressure and compliance.

    Sure, you can tweak your shock to provide more platform, thatís a given, but what youíre suggesting is utter nonsense.

    The real issue is why have bike manufacturers chosen to drop the BB so low?

    I have current model/geo bikes that vary from 330-345mm in BB height. I prefer the 345mm height for reduced pedal strikes, and I notice no difference in ride quality or handling.

    I also run 165mm cranks on all my bikes.

    Quote Originally Posted by kosmo View Post
    No free lunch! Low BB gives freaking awesome handling, cornering, etc. on reasonably smooth trails. Higher BB gives awesome pedaling on really chunky pedaling and/or climbing trails.

    You just have to find the compromise BB height that works for you and your main riding area. For me, ~335 on my 115 bike and ~340 on my 130 mm bike works well. Sometimes, I wish for lower when I'm blasting down a flow trail, and sometimes I wish for a bit higher on a long day of chunky pedaling.

    Rear suspension support matters, too. Sometimes just inserting a slightly larger volume reducer in the shock makes a noticeable difference with pedal strikes. The worst bike I ever had in this regard was an old, old Epic. Low BB, locked out until it wasn't, then once the brain opened, it was kinda like a trap door opening -- bam, down to the bottom! Not a great feature at the end of an exhausting endurance race.
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  17. #17
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    Quote Originally Posted by Nurse Ben View Post
    So Iím calling BS on the improved handling that comes from a reduction in BB height of 5-10mm. Seriously, no one but a pro could tell the difference, itís just not enough especially when you consider all the other variables like seat and bar height, crank length, shoe/pedal thickness, even tire pressure and compliance.

    Sure, you can tweak your shock to provide more platform, thatís a given, but what youíre suggesting is utter nonsense.

    The real issue is why have bike manufacturers chosen to drop the BB so low?

    I have current model/geo bikes that vary from 330-345mm in BB height. I prefer the 345mm height for reduced pedal strikes, and I notice no difference in ride quality or handling.

    I also run 165mm cranks one all my bikes.
    Hmmm. Never seen any nonsense coming from Kosmo, utter or otherwise.
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    Quote Originally Posted by JMac47 View Post
    Hmmm. Never seen any nonsense coming from Kosmo, utter or otherwise.
    Me neither, I just made it, bored I guess.
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  19. #19
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    I thought the handling difference between a moderate and low BB was pretty obvious.

  20. #20
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    Quote Originally Posted by Forest Rider View Post
    My 2016 Stumpjumper FSR (29x2.3) AND my 2019 Chameleon (27.5x2.8) has higher BB height than my year 2000 26" Stumpjumper hard tail.

    I struggle over the idea of today's bikes having low BB height. It's a continual comment but I have yet to have somebody post the actual height of their new bike relative to their previous bike.

    I'm not saying it isn't true. It's just that I have not personally seen a spec indicating a lower height than they used to be on small bikes.
    That bike from the year 2000 almost certainly had a fork with less travel than your new Chameleon, and it definitely had less travel front AND rear than your FSR. Of course they will/should have higher bottom brackets.

    I'm tired of some riders from certain areas telling other riders from other areas that they need more skill to avoid pedal strikes. It's not always skill. Sometimes it's a requirement to pedal through chunky terrain.

    Perhaps those people defending ridiculously low bottom brackets need to learn the skills to corner properly.

  21. #21
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    Quote Originally Posted by jeremy3220 View Post
    I thought the handling difference between a moderate and low BB we're pretty obvious.
    This^^^^. At least that's what the latest marketing angle is anyway. 😎
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    Quote Originally Posted by mountainbiker24 View Post
    That bike from the year 2000 almost certainly had a fork with less travel than your new Chameleon, and it definitely had less travel front AND rear than your FSR. Of course they will/should have higher bottom brackets.

    I'm tired of some riders from certain areas telling other riders from other areas that they need more skill to avoid pedal strikes. It's not always skill. Sometimes it's a requirement to pedal through chunky terrain.

    Perhaps those people defending ridiculously low bottom brackets need to learn the skills to corner properly.
    You can tune into YouTube anytime you want and see people riding every sort terrain possible.

    Riding the same low bb bikes we are.

  23. #23
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    The new bike is always shitty, never buy it.
    They will tell u in 3 months.
    My saddle and seatpost are 20 years old they do the job.

  24. #24
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    Quote Originally Posted by jeremy3220 View Post
    I thought the handling difference between a moderate and low BB we're pretty obvious.
    I can definitely feel the difference. The moment I got on my recluse for the first time I just felt uncomfortable. Like I felt tippy and teetery.
    My 958 feels completely different.

    Also 5-10mm at the bb is same as 1-2 degree head angle change or 10mm at the chainstays.

    But really I think it's bb drop that's more important. I think that may be why my 29er feels so amazing in corners.

  25. #25
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    Okay, now youíre comparing BB height to head tube angle and chainstay length?

    Please lord, take me now!

    Quote Originally Posted by Kevin Van Deventer View Post
    I can definitely feel the difference. The moment I got on my recluse for the first time I just felt uncomfortable. Like I felt tippy and teetery.
    My 958 feels completely different.

    Also 5-10mm at the bb is same as 1-2 degree head angle change or 10mm at the chainstays.

    But really I think it's bb drop that's more important. I think that may be why my 29er feels so amazing in corners.
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  26. #26
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    Quote Originally Posted by jeremy3220 View Post
    I thought the handling difference between a moderate and low BB was pretty obvious.
    It is, same reason super/sports cars are low to the ground. I personally dont like low BB bikes since I need to pedal to where they're beneficial. On a down hill trail with lifts low is great. It is easier to change direction on a higher BB bike.

  27. #27
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    Quote Originally Posted by Nurse Ben View Post
    Okay, now youíre comparing BB height to head tube angle and chainstay length?

    Please lord, take me now!
    I can't think of any bike fit measurement where a 10mm change isn't noticeable.

  28. #28
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    Quote Originally Posted by jeremy3220 View Post
    I can't think of any bike fit measurement where a 10mm change isn't noticeable.
    That's what I was getting at

    It must also be pointed out that 10mm at the bb is magnified because as you lean the bike it is like a lever.

    And you can't tell me that if you run 2.3 tires and the switch to 2.8 that you can't feel the difference in height.
    So if you are saying that 340mm is low what is not low? 350? 360? Which is a difference of 10-20mm.

    Also it is not lost on me that we are arguing 30mm or an inch and a half.

  29. #29
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    Quote Originally Posted by Mr. Blue Sky View Post
    I've had a few modern frames lately and, although I love 425mm chainstays, a bit more travel and slacker head angles, it all goes in the toilet when I have ridiculous pedal strikes. One hardtail frame I really wanted to love in particular, even with 170mm cranks was catching roots and small rocks all the time!
    I'm not a fan of low BBs since I ride chunky terrain. So I avoid them. I've been able to find bikes with short CS, slack HTA and reasonable BB heights. No issues with how a higher BB bike handles.
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  30. #30
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    Quote Originally Posted by Kevin Van Deventer View Post
    You can tune into YouTube anytime you want and see people riding every sort terrain possible.

    Riding the same low bb bikes we are.
    Don't see much technical climbing on YouTube, and I've seen even less videos where you can see the pedals.

  31. #31
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    I can think of many, but itís not worth the effort.

    Damn snow, I could use a good ride, skiing just ainít the same.

    Quote Originally Posted by jeremy3220 View Post
    I can't think of any bike fit measurement where a 10mm change isn't noticeable.
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  32. #32
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    Quote Originally Posted by Kevin Van Deventer View Post
    You can tune into YouTube anytime you want and see people riding every sort terrain possible.

    Riding the same low bb bikes we are.
    Which is not very useful given halo/hero runs and cuts-n-edits.
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  33. #33
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    It is not just pedal strikes, for those of us that no longer have any "ups,", but also clearance over logs, big rocks, and high rise shelf rock for chainrings. Anything under 13" is too low, for what I am capable of, and I prefer 13.5" to 14." I think the low bottom brackets are fine for those that need a stable down hill bike, but the higher brackets are more appropriate for mere mortals. I can ratchet my ass off in rock gardens, but I'm still catching a lot more stuff inadvertently with low bottom brackets and long crankarms. I'm currently on a bike with 170's and just under 340 and enjoying it nicely. I think the handling factor on most trails for most of us has more to do with the dynamics of HOW we are riding the bike and traction than bottom bracket height. Notice I said "I think:" firm opinion, stated diplomatically.

  34. #34
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    Quote Originally Posted by mountainbiker24 View Post
    Don't see much technical climbing on YouTube, and I've seen even less videos where you can see the pedals.
    I do not either, seem like more sit and spin up and shred down... I dont see reviews, adverts, super popular YouTube vids on chunky tech much. Hard to put into words, its more what I think of "west coast" good elevation...long climbs almost fire road like with fast swoopy downs, often with rocks, roots and drops but enough momentum that low BB would never be an issue (easy to time your strokes with momentum) and always seem to have a clear direction. We do not have those long downhill runs here (PA/NJ), we are constantly going up and down on trails that are fun either direction so sometimes you have to slowly crank up and over some chunky stuff.

    Some models are clearly off the rails with the extreme long low slack thing but on many the BB height is tuff to figure out without a good long test ride, a lower BB might get you less strikes than a higher one if the bike doesn't squat into the travel as much as the higher BB model

    I was constantly hitting pedal on my 2014 Spec with 338mm BB and NEVER on my 2019 Intense Primer with a 337mm. Now the Primer felt a bit to stiff, shock was just not active enough so I swapped the link to a slightly less progressive one and changed out the rear shock... same BB hight, same geo but almost perfectly split the difference in feel/pedal strikes between the 2014 Spec Stump and the stock Intense Primer. 3 set ups all with basically the same BB height and same travel but 3 very different outcomes.

  35. #35
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    Quote Originally Posted by HHL View Post
    It is not just pedal strikes, for those of us that no longer have any "ups,", but also clearance over logs, big rocks, and high rise shelf rock for chainrings. Anything under 13" is too low, for what I am capable of, and I prefer 13.5" to 14." I think the low bottom brackets are fine for those that need a stable down hill bike, but the higher brackets are more appropriate for mere mortals. I can ratchet my ass off in rock gardens, but I'm still catching a lot more stuff inadvertently with low bottom brackets and long crankarms. I'm currently on a bike with 170's and just under 340 and enjoying it nicely. I think the handling factor on most trails for most of us has more to do with the dynamics of HOW we are riding the bike and traction than bottom bracket height. Notice I said "I think:" firm opinion, stated diplomatically.
    You are spot on, pedal clearance and BB clearance have decreased and it's playing havoc with mountain biking. Perhaps a low BB helps newer riders, but it makes it miserable for those of us who know how to ride.

    I suspect the changes in trail development, to a more flow orientation, is the reason the bikes are being dumbed down.

    I liken the difference between a flow bike and a mountain bike to off and on piste skis.
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  36. #36
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    My 09 fsr xc comp has bb of 13.10, my abajo peak has 13.5. 26 vs 29. I ve noticed fewer pedal strikes with abajo.

  37. #37
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    Quote Originally Posted by Nurse Ben View Post

    I suspect the changes in trail development, to a more flow orientation, is the reason the bikes are being dumbed down.
    Nope. Its what ever the general public asks for, or in our case what is perceived as popular.

    Im happy having 13" under the crank arm at spindle, we have some huge rock gardens. some you try and ride through, some walking through is best. I live in mtb heaven and within 30 minutes there are 20 trails, and all of them different in what to expect, less one thing they all have some pretty steep canyon climbs.

  38. #38
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    Down right dangerous i would say... Having to go to 165's and still striking alot I'm searching for something with more reasonable bb drop.

    If you ride machine cut/groomed smooth trails... Ya no problem.

    I like primitive trails with rocks and techy obstacles = Low bb problematic.



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  39. #39
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    I think there is a tendency to try to "put a number on it". For me 12.75 inches (323mm) on my HT was too low. 13.25in (336mm) on my FS was also too low with 175mm crank arms. But this is the underlying problem. Is the bike HT or FS? Squishy fat, plus or not so squishy skinny tires? What is the rider's weight, what is the sag, what is the anti-squat? Then riding style, terrain, skill level? Is it an endurance bike, race bike, casual trail day?

    I'm in agreement that BBs are too low too much of the time. But there is a reason most manufactures don't even list BB height, and list a more nebulous BB drop number instead. They don't have any better of a system to express how a given BB height will impact the rider than we do.

    I used online compare tools to compare at least a dozen bikes before I bought my new FS. It was for a host of reasons, but one was to insure that I wasn't buying an experiment of an even lower BB. In general it is up to the consumer to figure out a way to deal with it if they deem it is an issue. Much like stem length, and seat rail position, I know I'm probably looking at contact point changes if I feel the BB is too low. It stinks that crank sets aren't cheap, but for me it is worth it.

  40. #40
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    Quote Originally Posted by adaycj View Post
    I'm in agreement that BBs are too low too much of the time. But there is a reason most manufactures don't even list BB height, and list a more nebulous BB drop number instead. They don't have any better of a system to express how a given BB height will impact the rider than we do.
    I agree BBs are generally too low for chunky/techy terrain and that a lot of factors come into play so two bikes with 13.5" BBs in the geo chart may have quite different rates of pedal strikes for the same rider out on the trail.

    One thing I don't agree with is that BB Drop is nebulous or misleading. BB drop is a more accurate way to describe BB height since it takes out of the equation tires. If you just use BB height you have to then figure out what tires the bike had on when the measurement was taken. Sometimes that is clear and sometimes it is not. If you know the BB drop you can compare two frames more easily.

    Getting both BBH and BB drop in the geo chart is nice.
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    Iím pretty sure the low BB height issue is primarily on FS bikes, hardtails are less problematic because the BB height varies less in use.
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    if this has already been brought up - please forgive me.

    i had 170 mm cranks specced on a particular bike, so i thought i could get away with smaller tires and lower BB. turned out the cranks were actually 175s that they had drilled at 170. so there was the extra 5 mm at the end. i didn't notice this at the time, and i had a bad crash due to crank strike. stayed off the bike for 3 weeks or so. lucky i didnt break anything. just something to consider. need to make sure of your crank length.
    i have true 165s on one of my bikes now.

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    Quote Originally Posted by kosmo View Post
    No free lunch! Low BB gives freaking awesome handling, cornering, etc.
    All a myth that bike industry made people fall for.

    Considering your center of gravity is about ~4 ft. high off the trail and can be adjusted by raising or lowering your body especially with a dropper posts...that few mm difference at the bottom bracket between lower and higher BB has zero affect on handling and cornering but has 100% effect on pedal strikes vs. no pedal strikes.

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    Quote Originally Posted by be1 View Post
    i had 170 mm cranks specced on a particular bike, so i thought i could get away with smaller tires and lower BB. turned out the cranks were actually 175s that they had drilled at 170. so there was the extra 5 mm at the end.
    That's freaking outrageous...

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    Quote Originally Posted by prj71 View Post
    All a myth that bike industry made people fall for.

    Considering your center of gravity is about ~4 ft. high off the trail and can be adjusted by raising or lowering your body especially with a dropper posts...that few mm difference at the bottom bracket between lower and higher BB has zero affect on handling and cornering but has 100% effect on pedal strikes vs. no pedal strikes.
    I think the greater BB drop is primarily what gives the increase in stability. Either way the difference is pretty obvious. I understand why some don't think the lower BB is worth the trade-offs but I don't understand how you guys can't tell any difference other than more pedal strikes.

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    My current bike (Mach 5.5) is specc'd at .2" higher than my old one (2005 SC Heckler), yet I seem to get a lot more pedal strikes, and for the first time ever one sent me off the bike a few weeks ago. 175mm cranks on both. I haven't actually measured actual bike to bike but seems odd. I suppose I am riding deeper in the travel possibly. Not a huge concern as I just try and pay attention and time my pedal strokes. I just find it odd. I am running slightly smaller tires than factory on the new one and larger on the old, but the difference is really noticeable. We do ride a lot of chunky stuff too. However if increased pedal strikes are the tradeoff between the two bikes, I'll take it.

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    Quote Originally Posted by be1 View Post
    if this has already been brought up - please forgive me.

    i had 170 mm cranks specced on a particular bike, so i thought i could get away with smaller tires and lower BB. turned out the cranks were actually 175s that they had drilled at 170. so there was the extra 5 mm at the end. i didn't notice this at the time, and i had a bad crash due to crank strike. stayed off the bike for 3 weeks or so. lucky i didnt break anything. just something to consider. need to make sure of your crank length.
    i have true 165s on one of my bikes now.
    Seems the norm on 175->170 cranks.
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    Quote Originally Posted by JMac47 View Post
    Seems the norm on 175->170 cranks.
    all of my other 170 cranks didnt have the extra 5 mm. it's not normal. it's a cost-saving measure.

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    Your Mach 5.5 has a pretty long wheelbase, so that may have something to do with it. It is going to take you longer to clear the obstacle in the bottom bracket area than a shorter bike: eg., Jeeps clearing boulders better than a full-sized pickup on up and down trails.

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    Quote Originally Posted by jeremy3220 View Post
    I think the greater BB drop is primarily what gives the increase in stability. Either way the difference is pretty obvious. I understand why some don't think the lower BB is worth the trade-offs but I don't understand how you guys can't tell any difference other than more pedal strikes.
    Same I can clearly feel it I actually work that shit. The bb drop and the weight distribution make we want to get as low on the bike as I can. It's encouraging me nail my technique because the capability is so high.

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    Quote Originally Posted by HHL View Post
    Your Mach 5.5 has a pretty long wheelbase, so that may have something to do with it. It is going to take you longer to clear the obstacle in the bottom bracket area than a shorter bike: eg., Jeeps clearing boulders better than a full-sized pickup on up and down trails.
    Good point. I just built a custom hardtail and set the BB height based on another hardtail [actually rigid] I ride and love. Assumed I wouldn't have low BB issues so I didn't include ISCG tabs for a taco bash. One of my first rides I was charging over a large rock and hit my dang chainring hard. Turns out the much longer bike with a suspension fork puts the BB in harms way a lot more than my old bike.

    So I got a MRP ISCG adapter and a mini-taco bash. I seem to hit it about once a ride. Not a lot, but without the bashguard my chain and chainring would eventually get KIA'd and force me to do the walk of shame.

    Interestingly with 170mm cranks and thin pedals I am not having notable pedal strike issues just the low BB/chainring. My other bike has 175mm cranks. So the shorter cranks seem to make enough difference to mitigate this issue.

    If I ever re-powdercoat this frame I am welding on ISCG tabs!
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    Quote Originally Posted by HHL View Post
    Your Mach 5.5 has a pretty long wheelbase, so that may have something to do with it. It is going to take you longer to clear the obstacle in the bottom bracket area than a shorter bike: eg., Jeeps clearing boulders better than a full-sized pickup on up and down trails.
    Good point! I missed that part....

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    This is an interesting thread and thank you to all of you that contributed.

    With shorter cranks, the legs aren't spread as wide. This raises your center of gravity. With shorter cranks, riding seated also requires raising the seat to get full leg extension. If you are having to ride shorter cranks due to pedal strikes, than the low BB benefits of lowering your center of gravity are probably being offset. What's the point?

    There does become a point where we are all worried about minutia, looking for ways to justify more purchases. I get it if we are all professional racers and every millisecond counts. But for most of us, these minor details that may indeed make a minute difference end up wasting a lot of money chasing the perfect setup. Really it's probably best to just go out and ride what you have, become one with it, improve your skills, and not worry so much if you have to hike-a-bike over a rocky section; learn other approaches to deal with off camber stuff, just deal with it.

    I just got back from a Thanksgiving camping trip where we rode at Santos in FL and Big Creek in Roswell GA. My daughter ended up hijacking my Nimble 9 hardtail, leaving me to ride the dirt jumper I had brought along for fun at the campsite. Short cranks, huge gear, very high BB, stiff fork, skinny tires, steep HA and yet I still managed to have a blast and rode all the trails I would have. We are not racing, just regular people having fun on bikes.

    These are first world problems....

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    Shorter cranks only raise your center of gravity when you've shifted all of your weight to one pedal. It's not the apex of a corner (very dynamic point) that you need the stability so much as everywhere in between. Also, on higher speed trails you don't need to weight the outside pedal much.

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    Quote Originally Posted by jeremy3220 View Post
    I think the greater BB drop is primarily what gives the increase in stability. Either way the difference is pretty obvious. I understand why some don't think the lower BB is worth the trade-offs but I don't understand how you guys can't tell any difference other than more pedal strikes.
    Because that few mm difference at the bottom bracket makes no difference in handling and cornering because center of gravity is up near your ass on the seat. But it does make a difference in pedal strikes vs. no pedal strikes.

    Thinking otherwise is just in your head.

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    Greater handling is a subjective term. Since the center of mass Is between the hips and shoulders depending on how much muscle or fat someone has. To lower the center of gravity you bend your knees and flatten your back. So longer reach and lower seat and top tubes do more for corners than BB height.
    A low BB gives a greater sense of stability. Since there is less pitching of weight. So you feel less movement when braking and turning. This is more of a confidence builder than an effect on handling. But if you are more confident you will brake less. This does have an effect on changing direction. A higher BB is better for an S-turn situation since the COM can be changed faster.


    I still like low BB on down hill bikes since the speed is greater and controlling body pitch isn't something I need to think about.

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    Quote Originally Posted by prj71 View Post
    Because that few mm difference at the bottom bracket makes no difference in handling and cornering because center of gravity is up near your ass on the seat. But it does make a difference in pedal strikes vs. no pedal strikes.

    Thinking otherwise is just in your head.
    The BB drop on my Megatower is 33mm. With the amount of sag it has that results in a pretty low BB. The difference between a BB 5mm higher and it is 22%. That's a 22% increase in leverage (due to the lever arm increasing 22%) between the BB and axles. That in addition to the lower CoG is why the difference in handling is so noticeable. It's very odd you can't tell if one of your contact points moved by over 20%.

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    Quote Originally Posted by Cerberus75 View Post
    A low BB gives a greater sense of stability.
    The lower BB literally changes the roll rate of the system. It's an objective change.

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    Quote Originally Posted by jeremy3220 View Post
    The BB drop on my Megatower is 33mm. With the amount of sag it has that results in a pretty low BB. The difference between a BB 5mm higher and it is 22%. That's a 22% increase in leverage (due to the lever arm increasing 22%) between the BB and axles. That in addition to the lower CoG is why the difference in handling is so noticeable. It's very odd you can't tell if one of your contact points moved by over 20%.
    5mm is ~3/16" of inch. Not very much change near the ground.

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    Quote Originally Posted by prj71 View Post
    5mm is ~3/16" of inch. Not very much change near the ground.
    Ah yes, 5mm is smaller the closer to the ground you are. Solid argument. /s

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    Quote Originally Posted by prj71 View Post
    All a myth that bike industry made people fall for.

    Considering your center of gravity is about ~4 ft. high off the trail and can be adjusted by raising or lowering your body especially with a dropper posts...that few mm difference at the bottom bracket between lower and higher BB has zero affect on handling and cornering but has 100% effect on pedal strikes vs. no pedal strikes.
    Yup, pretty much a myth perpetuated by people who aren't engineers and by bike manufacturers who want to sell an idea.

    Simple math is all that's necessary:

    5mm is what percentage of 1200mm?
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    Quote Originally Posted by Nurse Ben View Post
    Simple math is all that's necessary:

    5mm is what percentage of 1200mm?
    100% irrelevant

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    Quote Originally Posted by prj71 View Post
    All a myth that bike industry made people fall for.

    Considering your center of gravity is about ~4 ft. high off the trail and can be adjusted by raising or lowering your body especially with a dropper posts...that few mm difference at the bottom bracket between lower and higher BB has zero affect on handling and cornering but has 100% effect on pedal strikes vs. no pedal strikes.
    Not correct. BB height has to do with the BBD, or BB drop, which is the distance between the height of the BB and the center of the wheels. Have this negative and you'll have a hard time to even balance on a bike. The bigger BBD, more stable the bike will be.

    I can say that my bike has a BB some 5mm lower than my previous one, depending on frame settings. At first I have several pedal strikes. After I got used to it, I'm faster with less (or the same) number of strikes. Remember, we're talking of a 5mm difference on a BBD from 25 to 30mm.

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    Quote Originally Posted by jeremy3220 View Post
    100% irrelevant
    So is most of this discussion and your point is?

    I mean really, we got a guy comparing a 10mm change in BB height to a half degree change in HTA.

    Then we got a guy who actually thinks he rails a corner way better because his BB is 1/4" lower.

    Seriously, this is some pretty ludicrous stuff, at what point has this low BB benefit nonsense jumped the shark?

    I would agree that raising the BB too much, like lowering the BB too much, could lead to problems, but we're talking about 5-10mm, not enough to matter in regards to handling, but clearly (based on rider feedback) enough to increase pedal strikes.

    What sucks is that I've had to reduce my crank length to 165mm to make my bikes rideable, and the BB is still too low.

    My BB threshold is 340mm for all mountain, and 345 for rock crawling, anything less is a PITA.
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    [QUOTE=jeremy3220;14457275]100% irrelevant[/QUOTE


    Don't know where you got the 22%/5mm BS but it seems pretty irrelevant to me.I think you should give up on math and go ride.

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    [QUOTE=joecx;14458035]
    Quote Originally Posted by jeremy3220 View Post
    100% irrelevant[/QUOTE


    Don't know where you got the 22%/5mm BS but it seems pretty irrelevant to me.I think you should give up on math and go ride.
    From the people who say it doesn't matter. I did fine in all my calculus/Diff. E courses.

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    [QUOTE=jeremy3220;14458063]
    Quote Originally Posted by joecx View Post

    From the people who say it doesn't matter. I did fine in all my calculus/Diff. E courses.
    Whatever, I'm done with this idiotic discussion

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    Quote Originally Posted by Nurse Ben View Post

    I would agree that raising the BB too much, like lowering the BB too much, could lead to problems, but we're talking about 5-10mm, not enough to matter in regards to handling, but clearly (based on rider feedback) enough to increase pedal strikes.
    BB drops and heights are relatively short distances so yeah 5-10mm is a big change. Decreasing your reach or chainstay length by 10mm are less drastic changes. I can feel the difference in my hardtail and enduro bike with the hardtail being easy to tip side to side. BMX bikes with their high BB (positive BB drop I think) are ultra obvious. I can tell the order of my three bikes' BB drop even though I haven't actually calculated the BB ride heights.

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    Low bb height and pedal strikes.

    Just a quick question as it seems many if you may know. I have an Intense Primer that came with a 34 130 fork. Iím considering a 34SC 120. It will suit my XC style more. I do not tend to have a lot of strikes now. I also run the rear shock in the 115 mode all the time. Lastly I run the sag at 25 percent and like a firm pedal platform. Will the 10mm shorter fork drop the BB height much? Any guesses if it would be substantial? HTA affect? Thanks in advance!



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    Quote Originally Posted by trmn8er View Post
    Just a quick question as it seems many if you may know. I have an Intense Primer that came with a 34 130 fork. Iím considering a 34SC 120. It will suit my XC style more. I do not tend to have a lot of strikes now. I also run the rear shock in the 115 mode all the time. Lastly I run the sag at 25 percent and like a firm pedal platform. Will the 10mm shorter fork drop the BB height much? Any guesses if it would be substantial? HTA affect? Thanks in advance!



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    I'd say 3mm per 10mm change in fork length is about average. You could strap a large velcro strap to the crown and arch to limit travel to see how you like it.

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    Quote Originally Posted by trmn8er View Post
    Just a quick question as it seems many if you may know. I have an Intense Primer that came with a 34 130 fork. Iím considering a 34SC 120. It will suit my XC style more. I do not tend to have a lot of strikes now. I also run the rear shock in the 115 mode all the time. Lastly I run the sag at 25 percent and like a firm pedal platform. Will the 10mm shorter fork drop the BB height much? Any guesses if it would be substantial? HTA affect? Thanks in advance!



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    You can do an extended crown race or crown race spacer to make up for this if you want to keep the geo while going lighter with the fork.

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    Quote Originally Posted by fmendes View Post
    Not correct. BB height has to do with the BBD, or BB drop, which is the distance between the height of the BB and the center of the wheels. Have this negative and you'll have a hard time to even balance on a bike. The bigger BBD, more stable the bike will be.
    That is absolutely not true.

    Explain how nobody ever complains about balance on these bikes:


    Low bb height and pedal strikes.-bromp.jpg

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    Quote Originally Posted by syl3 View Post
    That is absolutely not true.

    Explain how nobody ever complains about balance on these bikes:


    Click image for larger version. 

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    I don't know what that is but as I mentioned before BMX bikes have a positive BB drop and it's very noticeable how twitchy that makes the bike side to side. That doesn't mean it's hard to balance per se, it suits its purpose well, but that purpose isn't rough high speed mtb trails.

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    Quote Originally Posted by syl3 View Post
    That is absolutely not true.

    Explain how nobody ever complains about balance on these bikes:


    Click image for larger version. 

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    Better yet, explain why anyone would ride that. I can't imagine someone riding that and not complaining about it afterwards. LOL

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    Quote Originally Posted by Nurse Ben View Post
    So is most of this discussion and your point is?

    I mean really, we got a guy comparing a 10mm change in BB height to a half degree change in HTA.

    Then we got a guy who actually thinks he rails a corner way better because his BB is 1/4" lower.

    Seriously, this is some pretty ludicrous stuff, at what point has this low BB benefit nonsense jumped the shark?

    I would agree that raising the BB too much, like lowering the BB too much, could lead to problems, but we're talking about 5-10mm, not enough to matter in regards to handling, but clearly (based on rider feedback) enough to increase pedal strikes.

    What sucks is that I've had to reduce my crank length to 165mm to make my bikes rideable, and the BB is still too low.

    My BB threshold is 340mm for all mountain, and 345 for rock crawling, anything less is a PITA.
    Between this and railing about people breaking pr's on their new bikes I'm going to have to ignore.

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    Quote Originally Posted by Kevin Van Deventer View Post
    Between this and railing about people breaking pr's on their new bikes I'm going to have to ignore.
    More power to ya, just need to watch those ski tips as you jump the shark
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    Quote Originally Posted by be1 View Post
    all of my other 170 cranks didnt have the extra 5 mm. it's not normal. it's a cost-saving measure.
    I sit corrected.
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    I have a bike with a 425mm chainstay and a 308mm BB height (which is just over 12") and a 175mm crank. Yes, pedal strike is an issue if I'm not mindful of my pedal position cornering on technical single tracks. This thing handles well and rock steady on the downhills. I don't have to think about it, it is natural part of riding.

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    My Ripmo has 341mm BB and 175mm cranks. It has the lowest BB that I have ever owned and I got a lot of pedal strikes the first few months of riding it. I got better about the strikes and still get some, but I am constantly aware and am always thinking when I get close to something that I might strike so I flinch waiting for it. It is a mental thing now and I hate having that feeling! I am thinking about getting shorter cranks to help overcome the mental part of it.

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    Quote Originally Posted by ToYZiLLa View Post
    My Ripmo has 341mm BB and 175mm cranks. It has the lowest BB that I have ever owned and I got a lot of pedal strikes the first few months of riding it. I got better about the strikes and still get some, but I am constantly aware and am always thinking when I get close to something that I might strike so I flinch waiting for it. It is a mental thing now and I hate having that feeling! I am thinking about getting shorter cranks to help overcome the mental part of it.
    It used to be a 13.4 inch BB height was plenty. But today's suspension travel on average bikes is ever increasing, and what was once a high BB is now low. An example is the Ripmo, a 6" travel bike. All of a sudden, a 13.4" BB height is low (assuming a rider is using sag and all of the travel). And if you don't want to strike pedals on a 6" travel bike, you're probably getting into the mid 14" BB heights, which is high by almost everyone's standards. I guess that leaves some riders decreasing sag or getting 165mm cranks.

  81. #81
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    Quote Originally Posted by JMac47 View Post
    I sit corrected.
    just something you need to verify depending on your cranks. some do it that way. some don't. if i had checked i would have saved some bruises. lesson learned.

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    Thatís not that low for a hardtail, compare to the Kona Honzo which has a 310mm bb height.

    Folks with pedal strike issues are on full suspension bikes for the most part.

    Quote Originally Posted by HotelBravo26 View Post
    I have a bike with a 425mm chainstay and a 308mm BB height (which is just over 12") and a 175mm crank. Yes, pedal strike is an issue if I'm not mindful of my pedal position cornering on technical single tracks. This thing handles well and rock steady on the downhills. I don't have to think about it, it is natural part of riding.
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    True, but the pedal strike issues are not generally happening while there is significant suspension compression, pedal strikes are a problem while pedaling, at or near sag.

    Quote Originally Posted by Pisgah View Post

    It used to be a 13.4 inch BB height was plenty. But today's suspension travel on average bikes is ever increasing, and what was once a high BB is now low. An example is the Ripmo, a 6" travel bike. All of a sudden, a 13.4" BB height is low (assuming a rider is using sag and all of the travel). And if you don't want to strike pedals on a 6" travel bike, you're probably getting into the mid 14" BB heights, which is high by almost everyone's standards. I guess that leaves some riders decreasing sag or getting 165mm cranks.
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  84. #84
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    Get 165mm cranks and never look back. You wonít notice any difference in performance, pedal strikes will greatly decrease, only issue will be raising seat and cockpit to accommodate shorter cranks.

    I havenít ridden anything longer than 165mm cranks for the last five years, my wife runs 160mm, my Muniís are all 150mm.

    Long cranks are from a bygone era when mountain bikes were simply road bikes with knobbies and flat bars.

    Quote Originally Posted by ToYZiLLa View Post
    My Ripmo has 341mm BB and 175mm cranks. It has the lowest BB that I have ever owned and I got a lot of pedal strikes the first few months of riding it. I got better about the strikes and still get some, but I am constantly aware and am always thinking when I get close to something that I might strike so I flinch waiting for it. It is a mental thing now and I hate having that feeling! I am thinking about getting shorter cranks to help overcome the mental part of it.
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  85. #85
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    Quote Originally Posted by Nurse Ben View Post
    Thatís not that low for a hardtail, compare to the Kona Honzo which has a 310mm bb height.

    Folks with pedal strike issues are on full suspension bikes for the most part.
    Well stated. Thank you for the insight, Nurse Ben.

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    I am totaly with post #84. For some trails my HT is much more fun with 165 and the negative side is more rumors if you ask me.

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    Quote Originally Posted by 33red View Post
    I am totaly with post #84. For some trails my HD is much more fun with 165 and the negative side is more rumors if you ask me.
    just got some 165s and it does feel different in a good way. feels more natural for my short legs. not aware of any negatives.

  88. #88
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    Quote Originally Posted by Nurse Ben View Post
    Get 165mm cranks and never look back. You wonít notice any difference in performance, pedal strikes will greatly decrease, only issue will be raising seat and cockpit to accommodate shorter cranks.

    I havenít ridden anything longer than 165mm cranks for the last five years, my wife runs 160mm, my Muniís are all 150mm.

    Long cranks are from a bygone era when mountain bikes were simply road bikes with knobbies and flat bars.
    165mm? I was thinking 170mm, but I was wondering if 5mm would really make any difference at all. What 165mm cranks are you running? Also how tall are you and what is your inseam?

  89. #89
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    Quote Originally Posted by ToYZiLLa View Post
    165mm? I was thinking 170mm, but I was wondering if 5mm would really make any difference at all. What 165mm cranks are you running? Also how tall are you and what is your inseam?
    6', typically wear a 34/35" inseam pant, sz 13 feet.

    I like SRAM GX DUB, DM chainrings from SRAM are quality and not expensive, a couple offset options. I run Shimano XT 8100 12 sp, previously ran GX 11sp, works great, same crank and chainring for both systems.

    I think the new Shimano XT 8100 12sp stuff comes in 165mm, not sure about the DM chainringe options cuz it's new

    Each 5mm is ~1/4", doesn't seem like much, but taken together a 10mm shorter crank will make a vary big difference in pedal strikes.
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  90. #90
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    I hate the new low BB trend. As an east coast rider itís one of the first specs I look at when buying a bike. Both my Devinciís I run in high mode as well.

  91. #91
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    Quote Originally Posted by Tinshield View Post
    I hate the new low BB trend. As an east coast rider itís one of the first specs I look at when buying a bike. Both my Devinciís I run in high mode as well.
    I agree; Iím 6í2Ē...175mm cranks are already downsized for me...I used to run 180mm cranks. I will add, that the issue is during climbing...not so much on the DH

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    Quote Originally Posted by Nurse Ben View Post
    6', typically wear a 34/35" inseam pant, sz 13 feet.

    I like SRAM GX DUB, DM chainrings from SRAM are quality and not expensive, a couple offset options. I run Shimano XT 8100 12 sp, previously ran GX 11sp, works great, same crank and chainring for both systems.

    I think the new Shimano XT 8100 12sp stuff comes in 165mm, not sure about the DM chainringe options cuz it's new

    Each 5mm is ~1/4", doesn't seem like much, but taken together a 10mm shorter crank will make a vary big difference in pedal strikes.

    Thanks for the info. I am 5'10 with a 32" inseam. Right now I am running with what came stock on the bike which is a 12sp SRAM NX drivetrain.

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    Quote Originally Posted by Dark Meat View Post
    I agree; Iím 6í2Ē...175mm cranks are already downsized for me...I used to run 180mm cranks. I will add, that the issue is during climbing...not so much on the DH
    Maybe you could try an easier gearing. My inseem is 34.5 and i love 165. All my bikes are geared to climb and i feel the smaller/shorter dead spot is usefull to climb but i accept the low speed. I just love not always needing to ratchet for some trails.

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    I climb a lot, nothing flat Sheri live. My long rides are generally +5k, much of it is 250-500í per mile, High Sierras, Cascades, and I do it all with 165mm cranks.

    Iíve ridden long cranks; most large frames come with 175mm cranks, it was only after I started riding muni and played with crank lengths ranging from 75-185mm that I really learned how much is enough and how much is too much.

    You owe it to yourself to try shorter cranks.

    Quote Originally Posted by Dark Meat View Post
    I agree; Iím 6í2Ē...175mm cranks are already downsized for me...I used to run 180mm cranks. I will add, that the issue is during climbing...not so much on the DH
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    This thread must have cursed me. Had my first pedal strike ejection in forever yesterday after a friend and I traded bikes for a bit. Maybe it was because of a low BB. Maybe because of riding deeper into the travel. Maybe it was because of longer cranks. Maybe it was because we can't see obstacles right now due to too many leaves. I dunno. All I know is it hurt like hell and I don't fancy doing that again any time soon!

  96. #96
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    This thread is pretty ridiculous.

    I've got a FS bike that I have more pedal strikes with on technical climbs. It's irritating AF, is what it is. When I built my hardtail, my various component choices raised the bb, but I only went 5mm shorter on the cranks (to 170mm). What I notice with shorter cranks is the change in gearing, and it's not something I'm a big fan of.

    I want/need low end gearing for climbing long, steep stuff and the shorter the cranks, the smaller the chainring needs to be to compensate. I'm not really willing to experiment too much with crank length because that means spending even more money on experimenting to get the gearing how I want it. In conversations with some of the aftermarket chainring manufacturers about other issues, they're cutting back on NW chainrings smaller than 30t as it is, which is not a trend that makes me happy. Maybe with other people using shorter cranks, it'll encourage the chainring mfrs to continue offering more smaller sizes. But it probably won't happen until the bike mfrs start equipping bikes with shorter cranks from the start.

    Anyway, the bb on my hardtail is at a height that I like. I haven't measured it, but the mfr's geo chart doesn't really help. I'm running a fork 20mm longer than stock, and I'm also on 29x2.6 tires. I definitely notice that I can crank through chunk that I have to slow down and clock my pedals for (and oftentimes still have a pedal strike) on my FS. That makes me happy. When it comes time to buy a new FS, I'll probably measure it finally and use it as a consideration in my purchase. My trails local trails don't really have lots of high speed corners, though. Sure, I notice lower bb as a benefit on stuff like that, but that's not what I ride most of the time.

    A high bb DOES help on some of the descents around me. A fair number of the descents are fairly ledgy (eroded root drops) and there are usually lots of them in series where they occur. I'll huck them when the landing zone looks good, but if I don't like the landing zone, I'm going to want to take them a bit slower. Increased clearance for the bb makes a difference with how large of a ledge I can "roll", or more accurately, how much I have to float the front wheel out away from the lip of the ledge before I let it drop down. Wheelbase is a factor here, too, of course, but if your bike is long and low enough, that almost completely eliminates that slow speed rolldown from your options. You have to float the front wheel so much that you're effectively just hucking the ledge anyway. The faster, more aggressive riders will gap some of them, but that riding style has never been me.

  97. #97
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    Quote Originally Posted by Harold View Post
    This thread is pretty ridiculous.

    I've got a FS bike that I have more pedal strikes with on technical climbs. It's irritating AF, is what it is. When I built my hardtail, my various component choices raised the bb, but I only went 5mm shorter on the cranks (to 170mm). What I notice with shorter cranks is the change in gearing, and it's not something I'm a big fan of.

    I want/need low end gearing for climbing long, steep stuff and the shorter the cranks, the smaller the chainring needs to be to compensate. I'm not really willing to experiment too much with crank length because that means spending even more money on experimenting to get the gearing how I want it. In conversations with some of the aftermarket chainring manufacturers about other issues, they're cutting back on NW chainrings smaller than 30t as it is, which is not a trend that makes me happy. Maybe with other people using shorter cranks, it'll encourage the chainring mfrs to continue offering more smaller sizes. But it probably won't happen until the bike mfrs start equipping bikes with shorter cranks from the start.

    Anyway, the bb on my hardtail is at a height that I like. I haven't measured it, but the mfr's geo chart doesn't really help. I'm running a fork 20mm longer than stock, and I'm also on 29x2.6 tires. I definitely notice that I can crank through chunk that I have to slow down and clock my pedals for (and oftentimes still have a pedal strike) on my FS. That makes me happy. When it comes time to buy a new FS, I'll probably measure it finally and use it as a consideration in my purchase. My trails local trails don't really have lots of high speed corners, though. Sure, I notice lower bb as a benefit on stuff like that, but that's not what I ride most of the time.

    A high bb DOES help on some of the descents around me. A fair number of the descents are fairly ledgy (eroded root drops) and there are usually lots of them in series where they occur. I'll huck them when the landing zone looks good, but if I don't like the landing zone, I'm going to want to take them a bit slower. Increased clearance for the bb makes a difference with how large of a ledge I can "roll", or more accurately, how much I have to float the front wheel out away from the lip of the ledge before I let it drop down. Wheelbase is a factor here, too, of course, but if your bike is long and low enough, that almost completely eliminates that slow speed rolldown from your options. You have to float the front wheel so much that you're effectively just hucking the ledge anyway. The faster, more aggressive riders will gap some of them, but that riding style has never been me.
    I ride 160mm until I travel to where you are. Then I bump it to 165mm crsnks. Doesn't seem like much but the effective gearing feels more natural and I can stay out of my 50t ring in the back for a few days (I tend to ride 10days straight when I visit WNC). I think there is now a 28t with XT 12speed at least I hope since I plane to switch drivetrains in 2020

    I have no real issues with 165mm in Pisgah with the tech climbs and can peddle through stuff easier than my home trails. Granted my BB is 13.5"

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    Quote Originally Posted by ToYZiLLa View Post
    I am thinking about getting shorter cranks to help overcome the mental part of it.
    A higher bottom bracket bike is the better solution. Don't have to think about it then anymore.

  99. #99
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    Low BB you say?? What could possibly go wrong?

    https://www.instagram.com/p/B50dEauFOKm/
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  100. #100
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    Quote Originally Posted by HotelBravo26 View Post
    I have a bike with a 425mm chainstay and a 308mm BB height (which is just over 12") and a 175mm crank. Yes, pedal strike is an issue if I'm not mindful of my pedal position cornering on technical single tracks. This thing handles well and rock steady on the downhills. I don't have to think about it, it is natural part of riding.
    Your bike would handle exactly the same if your BB height was 335mm. Except you wouldn't have to be mindful of your pedal position.

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    I swapped wheels on my Shred Dogg this weekend from 27.5 x 2.8 to 29 x 2.6, raising my BB from ~335mm to 350mm. Rode this morning on my back yard trails, got to this little three rock wall that is a 50/50 on my 27.5 set up because it's hard to work the pedals as you clamber over the rocks.

    This morning I literally rode straight over those rocks without ratcheting or pausing, all for the love of 15mm.

    Oh, and the bike handles fine
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  102. #102
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    E13 and RF SIXC also come in a 165mm length.

    I hated the low bb on my V2 Ibis Ripley (12.99"). It's what bums me out most about the bike. Now on an Evil Offering with 170mm cranks and I gotta admit it wasn't that big a deal making the switch from 175s. Not sure about 165s but for anyone on the fence about down-sizing I suggest giving it a try.

  103. #103
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    "Length 165mm, 170mm, 175mm We are proud to be the only manufacturer offering Trail cranks in 165mm length to accommodate the ultra-low bottom brackets".

    73mm spindle width in carbon only: $399

    RF Cranks can run different spindle lengths.

    Quote Originally Posted by rockman View Post
    E13 and RF SIXC also come in a 165mm length.

    I hated the low bb on my V2 Ibis Ripley (12.99"). It's what bums me out most about the bike. Now on an Evil Offering with 170mm cranks and I gotta admit it wasn't that big a deal making the switch from 175s. Not sure about 165s but for anyone on the fence about down-sizing I suggest giving it a try.
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  104. #104
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    I thought this was a pretty interesting discussion on the topic. https://www.daveypushbikes.com/blog/...tood-dimension
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  105. #105
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    Quote Originally Posted by Cerberus75 View Post
    I ride 160mm until I travel to where you are. Then I bump it to 165mm crsnks. Doesn't seem like much but the effective gearing feels more natural and I can stay out of my 50t ring in the back for a few days (I tend to ride 10days straight when I visit WNC). I think there is now a 28t with XT 12speed at least I hope since I plane to switch drivetrains in 2020

    I have no real issues with 165mm in Pisgah with the tech climbs and can peddle through stuff easier than my home trails. Granted my BB is 13.5"
    I'll say that I don't have very high power output so for me it's a bit more notable.

    What pisses me off is that just about every aftermarket chainring mfr discounted my desire for a 28t ring for shimano m9100. Now, I also use the 10-45 cassette because I don't want a long-ass cage derailleur, but in order to do it I had to use the Eagle quick link method and just buy a regular NW ring in 28t flavor. I use 170mm cranks with this configuration and I do notice that it's a little tougher to push than an 11-46 with 175mm cranks on a heavier bike. If I went shorter on the cranks, I could see wanting to run a 26t chainring or compromise with the long-ass cage and a 10-51 cassette. Neither of which I care to do.

    When I first set up this drivetrain, I was on a 30t Wolftooth ring (the Shimano XT 28t wasn't available yet) and it was just too big. I could push it for awhile, but I kept blowing myself up trying to push it all the way up the bigger climbs. If I were to do it over again right now, I'd probably get a Shimano crank and 28t Shimano ring. But I still don't think I'd go shorter than 170mm on the crank arms. Especially since nobody makes a 26t ring for those cranks at all. At any rate, I don't have any pedal strike problems at all with this configuration, so I'm happy with it.

  106. #106
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    I run SRAM GX Eagle 165mm crank, DUB BB, and SRAM Round NW 26t chainring. I prefer NW but the smallest made with the zero offset I need for my GG bikes is a 28t.

    I just changed from SRAM GX 11sp to Shimano XT 8100 12 sp 10-51, works like a champ.

    I don't think the derailleur cage length is an issue, at speed it's tucked up because you're pushing bigger gears, climbing through tech is low speed so it's really isn't all that exposed, and anyway the part you smack most is the derailleur body. I do a serious amount of boulder grinding, my derailleurs need a skid plate

    Dream bike: Pinion FS. Waiting on a suspension that works, even if an idler pulley is necessary

    I'd consider running a 165mm carbon crank, but I'd need to run boots cuz I smack a lot of rocks, which would further reduce clearance, so I'm sticking with aluminum for now.

    Quote Originally Posted by Harold View Post
    I'll say that I don't have very high power output so for me it's a bit more notable.

    What pisses me off is that just about every aftermarket chainring mfr discounted my desire for a 28t ring for shimano m9100. Now, I also use the 10-45 cassette because I don't want a long-ass cage derailleur, but in order to do it I had to use the Eagle quick link method and just buy a regular NW ring in 28t flavor. I use 170mm cranks with this configuration and I do notice that it's a little tougher to push than an 11-46 with 175mm cranks on a heavier bike. If I went shorter on the cranks, I could see wanting to run a 26t chainring or compromise with the long-ass cage and a 10-51 cassette. Neither of which I care to do.

    When I first set up this drivetrain, I was on a 30t Wolftooth ring (the Shimano XT 28t wasn't available yet) and it was just too big. I could push it for awhile, but I kept blowing myself up trying to push it all the way up the bigger climbs. If I were to do it over again right now, I'd probably get a Shimano crank and 28t Shimano ring. But I still don't think I'd go shorter than 170mm on the crank arms. Especially since nobody makes a 26t ring for those cranks at all. At any rate, I don't have any pedal strike problems at all with this configuration, so I'm happy with it.
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  107. #107
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    Quote Originally Posted by Nurse Ben View Post
    I run SRAM GX Eagle 165mm crank, DUB BB, and SRAM Round NW 26t chainring. I prefer NW but the smallest made with the zero offset I need for my GG bikes is a 28t.

    I just changed from SRAM GX 11sp to Shimano XT 8100 12 sp 10-51, works like a champ.

    I don't think the derailleur cage length is an issue, at speed it's tucked up because you're pushing bigger gears, climbing through tech is low speed so it's really isn't all that exposed, and anyway the part you smack most is the derailleur body. I do a serious amount of boulder grinding, my derailleurs need a skid plate

    Dream bike: Pinion FS. Waiting on a suspension that works, even if an idler pulley is necessary

    I'd consider running a 165mm carbon crank, but I'd need to run boots cuz I smack a lot of rocks, which would further reduce clearance, so I'm sticking with aluminum for now.
    hitting rocks isn't my concern. it's sticks that poke out everywhere. some of which aren't just loose debris, but they're roots that are attached and poke out. Those are the real derailleur eaters. How far "tucked up" the cage is doesn't matter much. The length and how much leverage gets put on it WHEN it snags something is what matters. The shorter the cage, the less likely it is to bend into the spokes when that happens, and the less real estate there is for it to snag on a stick in the first place.

    So long as I can get the gearing I want from a shorter cage derailleur, I have no reason to use a long-ass cage. Crank length plays into it, and if I don't have to run shorter than I have, then I also will not do that.

  108. #108
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    Quote Originally Posted by prj71 View Post
    Your bike would handle exactly the same if your BB height was 335mm. Except you wouldn't have to be mindful of your pedal position.
    Well, it doesnít happen often enough to shift the entire center of gravity of the bike up an inch, or run a bigger wheel. Iíve seen those on this thread with a 335+ BB height that also site pedal strike.

    Iíve gone from pedals to clip-ins and that solves the problem as well.

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    Only my opinion here, but it's not the low BB height. It's the LENGTH of the bike. Modern longer bikes sit lower over the obstacles. I can't draw a diagram on the forum, but it's just a basic triangle.

    Let's compare a 2 Door Jeep compared with a 4 door full size truck. Same ground clearance, but the big truck will high-center before the short Jeep. Same thing on your bike. The farther the wheels are apart (over a peak) the lower the bottom bracket.

  110. #110
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    Quote Originally Posted by itsnotbroken View Post
    Only my opinion here, but it's not the low BB height. It's the LENGTH of the bike. Modern longer bikes sit lower over the obstacles. I can't draw a diagram on the forum, but it's just a basic triangle.

    Let's compare a 2 Door Jeep compared with a 4 door full size truck. Same ground clearance, but the big truck will high-center before the short Jeep. Same thing on your bike. The farther the wheels are apart (over a peak) the lower the bottom bracket.
    It is back to the surfer comparaison.
    Some love long boards some love the short ones.
    I prefer a bike with less stability, more playfull.
    Some prefer differently.

  111. #111
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    Quote Originally Posted by 33red View Post
    It is back to the surfer comparaison.
    Some love long boards some love the short ones.
    I prefer a bike with less stability, more playfull.
    Some prefer differently.
    To his point, surfboards don't have to worry about getting high centered. On certain features/obstacles his point is valid. The longer the wheelbase the worse the break over angle will be which could lead to more opportunities to strike a pedal.

    And to your point, I prefer longer. Bikes that is... I suck at surfing.

  112. #112
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    Quote Originally Posted by itsnotbroken View Post
    Only my opinion here, but it's not the low BB height. It's the LENGTH of the bike. Modern longer bikes sit lower over the obstacles. I can't draw a diagram on the forum, but it's just a basic triangle.

    Let's compare a 2 Door Jeep compared with a 4 door full size truck. Same ground clearance, but the big truck will high-center before the short Jeep. Same thing on your bike. The farther the wheels are apart (over a peak) the lower the bottom bracket.
    and length of bike is mostly based on size of frame, so us big guys get screwed doubly.

    I think we all know how to use the terrain to reduce pedal strike, placing our wheels where they maximize clearance, so given that skill is more or less static, the low BB is an issue for all riders just to different degrees.
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    Advice from someone who's learned from the 'Families and Riding with Kids' forum -- short cranks are where it's at!

    One of the other advantages aside from fewer pedal strikes I don't see mentioned is that "needing to raise the seat" also equates to "can fit a dropper with more extension".

    I'm ~5'11" and have switched to 152 / 155mm cranks on all my bikes now.

    Trailcraft makes a nice direct mount crank (currently using their cranks on my primary bike -- a older Niner EMD 9 with a 308mm BB):
    https://www.trailcraftcycles.com/pro...-mount-cranks/


    If you want a cheap way to experiment, you could try what I did to test -- older bike with a square taper BB + cheap kids cranks (Suntour XCT Jr, $30) + 64 BCD 1x chainring (USA Made Components, $17).


    For those looking for a smaller 0mm offset chainring, I'd come across these at 26T (note that I haven't personally tried them and they do have some notes about incompatibility with some chains):
    https://www.ebay.com/itm/Narrow-Wide...-/252763752200

  114. #114
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    Quote Originally Posted by Nurse Ben View Post
    and length of bike is mostly based on size of frame, so us big guys get screwed doubly.

    I think we all know how to use the terrain to reduce pedal strike, placing our wheels where they maximize clearance, so given that skill is more or less static, the low BB is an issue for all riders just to different degrees.
    I find it terrifying when racing enduro. Very easy to make mistakes when putting out maximum effort sprinting out of corners and such.

    One such pedal strike cost me a broken collarbone, scapula, glenoid, and ribs. Maybe it would have happened anyway, hard to tell because I never saw what I clipped.

  115. #115
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    Quote Originally Posted by rockman View Post
    I find it terrifying when racing enduro. Very easy to make mistakes when putting out maximum effort sprinting out of corners and such.

    One such pedal strike cost me a broken collarbone, scapula, glenoid, and ribs. Maybe it would have happened anyway, hard to tell because I never saw what I clipped.
    I clipped a big rock sticking out of a small bank on the edge of the trail. I was skidding down the trail on my face before I even realized what happened. Rock was hiding in the grass and I never even saw it. BB height was irrelevant there though as my crank arms wasn't even in the down position. Certainly has made me more cautious and I ordered a full face helmet a couple days later. LOL

  116. #116
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    Quote Originally Posted by TimTucker View Post
    Advice from someone who's learned from the 'Families and Riding with Kids' forum -- short cranks are where it's at!

    One of the other advantages aside from fewer pedal strikes I don't see mentioned is that "needing to raise the seat" also equates to "can fit a dropper with more extension".

    I'm ~5'11" and have switched to 152 / 155mm cranks on all my bikes now.

    Trailcraft makes a nice direct mount crank (currently using their cranks on my primary bike -- a older Niner EMD 9 with a 308mm BB):
    https://www.trailcraftcycles.com/pro...-mount-cranks/


    If you want a cheap way to experiment, you could try what I did to test -- older bike with a square taper BB + cheap kids cranks (Suntour XCT Jr, $30) + 64 BCD 1x chainring (USA Made Components, $17).


    For those looking for a smaller 0mm offset chainring, I'd come across these at 26T (note that I haven't personally tried them and they do have some notes about incompatibility with some chains):
    https://www.ebay.com/itm/Narrow-Wide...-/252763752200
    Canfield Bikes has Gpx style cranks down to 145mm.

  117. #117
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    I hit a rock hiding in the grass, I was cranking full speed on a flow trail, pedal hit the rock and I went flying, fortunately I only suffered some bruising, but when it was all said and done I ended up a good twenty plus feet from where I hit the rock.

    Clipping trees with my bars has caused broken bones and messed up bikes, but that is all on me, whoops

    So I saw that Canfield had some short cranks on sale, but all the spindles were 83mm. I'd take a shorter crank if I could get it, esp for my longer travel bike.
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  118. #118
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    Clipping trees is more of a concern to me than a pedal strike- this is why I am reluctant to go wider with my bars. I still run "antique" bar ends and they've save my hands more than once. I still manage to bash my shoulder cutting a tree too close- fun!
    I race XC with a 2005 Raleigh M80. Yes, I really do.

  119. #119
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    Quote Originally Posted by Nurse Ben View Post
    I hit a rock hiding in the grass, I was cranking full speed on a flow trail, pedal hit the rock and I went flying, fortunately I only suffered some bruising, but when it was all said and done I ended up a good twenty plus feet from where I hit the rock.

    Clipping trees with my bars has caused broken bones and messed up bikes, but that is all on me, whoops

    So I saw that Canfield had some short cranks on sale, but all the spindles were 83mm. I'd take a shorter crank if I could get it, esp for my longer travel bike.
    If they dont have them in 73mm spindles they should soon. If you hit the contact tab on the website and ask them to let you know when a size you want is in. They'll let you know.

  120. #120
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    Quote Originally Posted by Cerberus75 View Post
    Canfield Bikes has Gpx style cranks down to 145mm.
    They do, but they're both heavier and more expensive than Trailcraft.

  121. #121
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    Quote Originally Posted by TimTucker View Post
    They do, but they're both heavier and more expensive than Trailcraft.
    It's about a wash with the weight. Since the Canfield cranks weight is with the BB. They are less expensive though. How durable are they?

  122. #122
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    Quote Originally Posted by Cerberus75 View Post
    It's about a wash with the weight. Since the Canfield cranks weight is with the BB. They are less expensive though. How durable are they?
    Trailcraft is 570g for 152mm cranks and 26t chainring, 690g once you add in the BB.

    Canfield shows 760g for 155mm cranks and BB. Doesn't look like the weight includes a chainring, which would put you even higher.

    Hard to assess durability myself since I haven't had any pedal strikes since switching, but they feel solid and there are some pretty hard riding kids over in the family forum and I've yet to hear of anyone breaking them.

  123. #123
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    What the heck is going on in this thread? Now we're sampling kids on 155mm cranks as a relevant data point??? Not only that but we're getting weight weenie about it at the same time? Awesome.

    And what would you say if someone said...

    The solution is is a properly designed bike, not 145mm cranks. (?)
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    Stop asking how much it weighs and just go ride it.

  124. #124
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    Quote Originally Posted by *OneSpeed* View Post
    What the heck is going on in this thread? Now we're sampling kids on 155mm cranks as a relevant data point??? Not only that but we're getting weight weenie about it at the same time? Awesome.

    And what would you say if someone said...

    The solution is is a properly designed bike, not 145mm cranks. (?)
    Meh, this thread hasn't made sense since a few posts back, Post #1 I'd say.

  125. #125
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    I used to ride a 650b converted Prophet. It had to be run in XC mode, so the BB was 19mm above the wheel axles. I think the clearance was 14.5" or something crazy like that. Cleared everything! But I got an Ibis Ripmo with 29 x 2.5 tires. It is not as tall as the Prophet, and it has the same length cranks. I think that it is almost 3/4" lower but I got used to it pretty quickly. It handles so much better.

    I ride New England rocks and roots. MA, NH and VT. Still like the Ripmo more. I also ride a Fat Bike with a lower BB, but without suspension, no troubles. I think you get used to what you ride. Some configurations are better to get used to. I am 5' 8" tall, 160 lbs and 56 years old. When the BB is below the centerline of the axles, the bike is more stable. Now that is not to say that you can't ride like that but I like the center of rotation below the BB.
    My name is Chris and I ride a Ripmo now.

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