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  1. #1
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    Shorter cranks on more aggressive rig?

    8 Hours Ago
    Could anybody help me make up my mind on going for shorter cranks on an AM/Enduro style bike? Iím in need of a new ring, cassette, and BB so now would be the time to do it. Iíve always ridden 175s on everything, Iím 6í1Ē with about 34Ē inseam. I am currently running the 175 cranks from my old bike which had a higher BB than what I am on now (12.4mm drop, 27.5, hefty sag).

    The advantage for pedal clearance is obvious, I scrape and catch my pedals more now and have to watch my timing more but Iím managing. Iím running platform pedals and tend to mash when Iím trying to keep the pace up so Iím a little afraid of losing torque / power to mash climbs and sprints. Does anyone think shorter helps any for control on jumps, manualing, technical terrain or hinders? It seems like longer might actually give more stability for handling since your legs are spread a touch more but I have heard the opposite can be true? I realize weíre talking a tiny change but Iím looking for opinions... 170, 165, or ride what I got? Thanks for any insight.

  2. #2
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    I recently went from 175 to 170 - primarily because all the new bikes have such low bottom brackets. Pedal strikes improved, and honestly, I find the 170s far more comfortable. I can't tell a difference on power in the slightest, I even think it's maybe more efficient - I do for sure notice my knees like the 170s better.

    I'm basically the same height as you, tempted to throw a 165 on next and test that on a Fuel EX.

    Walt posted some of his experiences with short cranks in the plus forum where he had positive results. However, a few people will invariably argue you lose power. Honestly it boils down to personal preference. In my experience, it's been a huge improvement.

  3. #3
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    I run a 170 on my FS rig and a 175 on my SS. I think the biggest thing I notice is that I don't notice really any difference. More importantly, I have not experienced any negatives with the shorter crank arm. I'm 5'8" so that may factor into it a little FWIW.

  4. #4
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    I am 6' and just put some 165 on my bike to gain pedal clearance. I cannot tell the difference from the 175 it replaced.


  5. #5
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    The taller you are, the less it matters I think.

    You mechanically already "fit" a 175mm crank. Im 5'7, I dont fit a 175mm crank. Even with 170's my knees sometimes end up at a weird angle that I cant apply power at.

    Ill admit that even at 5'7 the stallout feeling I get is pretty rare. Riding the same trail, I'll hit that weird stall out on only one section, and maybe once every 3rd or 4th ride. Id benefit from 165's I think.

  6. #6
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    Quote Originally Posted by One Pivot View Post
    The taller you are, the less it matters I think.

    You mechanically already "fit" a 175mm crank. Im 5'7, I dont fit a 175mm crank. Even with 170's my knees sometimes end up at a weird angle that I cant apply power at.

    Ill admit that even at 5'7 the stallout feeling I get is pretty rare. Riding the same trail, I'll hit that weird stall out on only one section, and maybe once every 3rd or 4th ride. Id benefit from 165's I think.
    An oval ring would help you with that stallout feeling you are getting as well

  7. #7
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    True, but I wonder if ovals are working around a crank length issue! I'll eventually try an oval, but I know stepping down a crank size would be a good move too.

    There's a ton of road focused articles on this, but mtb is finally coming around too.

  8. #8
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    I'm 6'1" and I recently put 165mm cranks on my Stache. I absolutely think that it was one of the best purchases I've made. I wrote my thoughts about them here. http://forums.mtbr.com/26-27-5-29-pl...l#post13769005
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  9. #9
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    5'4" here on a 2017 Fuel EX-8 27.5+. Went from the stock 175 cranks to 165 cranks. The best upgrade I did to my bike bar none. Pedal strikes are now the exception. I also went with 32T oval. Also, I noticed a smoother cadence on my climbing.

  10. #10
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    Quote Originally Posted by One Pivot View Post
    True, but I wonder if ovals are working around a crank length issue! I'll eventually try an oval, but I know stepping down a crank size would be a good move too.

    There's a ton of road focused articles on this, but mtb is finally coming around too.
    I'm 5'6" 165mm cranks with an oval, I may go to 160s I feel the oval more on tech climbs but it didn't solve the hitch at the top of too long of a crank when I ran 170s

  11. #11
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    Thanks for the discussion. I nearly ordered 165mm cranks but decided to compromise on 170mm for now and see how that goes. I didn't want to give up any seat clearance or change bar height, I feel like everything is fairly dialed as it is. I'm sure 170 won't be much of a change but I'm betting I'll like it.

  12. #12
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    I'm at the absolute minimum size with my new bike and 165s cranks. It's a 29er and I smash my taco all the time. Had I went with longer cranks (not recommended by bike company) I would've had to reduce the dropper stroke to fit.

  13. #13
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    Quote Originally Posted by One Pivot View Post
    The taller you are, the less it matters I think.

    You mechanically already "fit" a 175mm crank. Im 5'7, I dont fit a 175mm crank. Even with 170's my knees sometimes end up at a weird angle that I cant apply power at.
    This is true. A 6' 1" person can run just about any crank length. But the standard 175mm cranks are too big for lots of people. Sizing down isn't a big deal. Sizing up has disadvantages.

    The one advantage of having a shorter crank is being able to get a better hinge in attack position, or at least not needing quite as much flexibility. The farther your feet are in attack position, the more flexibility you need in your hamstrings to get the ideal position.

  14. #14
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    Quote Originally Posted by trailsnales View Post
    I realize weíre talking a tiny change but Iím looking for opinions... 170, 165, or ride what I got? Thanks for any insight.
    I've gone from 175mm cranks to 170mm cranks and back to 175mm cranks on three different bikes. The middle one had a lower BB hence the desire for shorter cranks. Within this ^^ limited range of length I did not notice any significant difference.
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  15. #15
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    I'm 5'6'', ride a 27.5 trail bike and low BBs are great but do have their downsides. My knees are also pretty rough so 165mm cranks work great for me and I almost never have pedal strikes unless it's really techy climbing and I'm not in a spot to ratchet. I do not find climbing to be any more of an effort. All pros and no cons in my book.
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  16. #16
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    It kind of blows me away how often this subject comes up of late. Part and parcel of the low BB's the bulk of bike companies are cramming down our throats these days.

    I like 170's.

  17. #17
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    Iíve always ran 175mmís on my mountain bikes since the eighties. Iím 5í7Ē and now running 165mm on my Evil Calling. I mistakenly thought I needed the length for levage power. Donít really notice any difference except pedal sticks seemed to be less and my hip flexors arenít as sore on long rides
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  18. #18
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    I just went 165 from 175 on my 29 HT that has a low BB, especially with the 650b+ I run in the winter. If there is a reduction in power I haven't noticed it yet. Spinning a smaller circle feels good and I'm glad I gave it a shot. I enjoy the low BB, but with big flat pedals and 2.8 650b tires I was having a bit of trouble in some spots.
    I got some bad ideas in my head.

  19. #19
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    I swapped from 175s to 170s at 5'11" and am never going back.

  20. #20
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    I'm seeing some pedal "scratches" on my Intense Primer when the rear Fox shock is in full travel position. But I am purposely riding that bike through techy situations such as baby heads and rock gardens.

    Not getting hard strikes but some "scratches"

    Bike Has Truvativ Stylo Eagle Boost GXP, 175mm cranks

    Was considering upgrading my wheels then cranks to something like the SRAM Dub XO1 or XX1 in 165mm but noticed they only come in 170 length.

    Difference between 170 and 175mm is a whopping 1/5th of an inch wondering if that would even make a difference and if I would be better off on 165's or 167.5"s?

    I'm 5'8" and ride a medium

  21. #21
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    Quote Originally Posted by newking View Post
    Not getting hard strikes but some "scratches"

    Bike Has Truvativ Stylo Eagle Boost GXP, 175mm cranks

    Was considering upgrading my wheels then cranks to something like the SRAM Dub XO1 or XX1 in 165mm but noticed they only come in 170 length.

    Difference between 170 and 175mm is a whopping 1/5th of an inch wondering if that would even make a difference and if I would be better off on 165's or 167.5"s?
    Difference for the pedals or for your body ergonomics?

    Doesn't sound like you have pedal strike issues as is, but 5mm can drastically reduce pedal strikes. Having moved from 175mm to 170mm and back to 175mm cranks I don't really notice that +/-5mm.
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  22. #22
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    I am 6í5Ē and swapped my 175 for 170 mm cranks for pedal clearance. I notice no downside as far as pedaling goes. Good improvement for pedal clearance though. If you are shorter I would not hesitate to try even shorter cranks.

  23. #23
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    Quote Originally Posted by newking View Post
    I'm seeing some pedal "scratches" on my Intense Primer when the rear Fox shock is in full travel position. But I am purposely riding that bike through techy situations such as baby heads and rock gardens.

    Not getting hard strikes but some "scratches"

    Bike Has Truvativ Stylo Eagle Boost GXP, 175mm cranks

    Was considering upgrading my wheels then cranks to something like the SRAM Dub XO1 or XX1 in 165mm but noticed they only come in 170 length.

    Difference between 170 and 175mm is a whopping 1/5th of an inch wondering if that would even make a difference and if I would be better off on 165's or 167.5"s?

    I'm 5'8" and ride a medium
    You can find the Dub NX and GX level in 165mm at Jenson's. I run 165mm on all my bikes.
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  24. #24
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    I don't really find that the "aggressiveness" of the bike or the riding itself really makes a difference in terms of pedal strikes.

    I run the same length on my 80mm HT as on my 140mm AM bike.
    15mm is a second-best solution to a problem that was already solved.

  25. #25
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    5'8" and new enduro bike came with 170s when I have always been used to 175. Haven't any pedal strike yet and my knees are happy with the extra clearance at top of stroke. Bike also has a 34T compared to when I used to run 32T, so cadence is about the same.

  26. #26
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    I am 6 feet tall and went from 175 to 165. My only regret is that I picked the wrong colour of crank arms. Should have stayed with black.

    Have a look on a ruler at how much 5 mm really is. It is almost imperceptible.
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