BB drop/ height on singlespeed bikes- Mtbr.com
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  1. #1
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    BB drop/ height on singlespeed bikes

    I read in a few places that having a high bottom bracket is essential for singlespeeding. I think that can be over-stated, but it's a worthwhile perspective to consider.

    purely from a handling standpoint and where it puts your center of gravity (not counting rock strikes), how high is too high? how low is too low? sweet spot?

    technically, if you wanted to, you could build a bike with the cranks several inches above the axles and have BB rise, but that would suck to ride. how high are you willing to go to avoid rocks before it raises your center of gravity too much?

    personal experience:
    I have a frame with a pretty darn low BB and 170mm cranks. I ride in some very rocky terrain with lots of white scars on the rocks from pedals and chainrings hitting them over the years. I don't worry too much about rock strikes, although they happen sometimes. the bike is very stable, but I am starting to second guess myself. I will have to measure to confirm, but I think my BB is less than 12" from the ground.

    is it possible that I don't get rock strikes because I ride conservatively, and the low BB is holding me back? there are several bikes on the market with a BB that is 10-15mm higher, which is a lot when it comes to BB drop.
    Last edited by mack_turtle; 08-14-2018 at 11:10 AM.

  2. #2
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    I find that bottom bracket height is sort of inconsequential after awhile (to a degree). Somehow, whether sub-conscious or intentional, pedal strikes sort of disappear. I think I have gotten better at just timing my stroke to avoid strikes and it's become somewhat automatic. I'm in some pretty rocky terrain too.

    That being said, I was riding with another MTBR guy awhile back and he commented about how high my BB was on my URT SS.
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  3. #3
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    I certainly do that too. I ratchet my pedal strokes quite a bit to avoid rocks. I know a higher BB will let me be more generous with the handling, but I don't know how much difference 1cm would make. It's all subjective but it could be significant.

  4. #4
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    I too ride in a very rocky area, and am currently on a Nimble 9 with a rigid fork. The bb is really low due to that frame being built around a bigger fork. The only thing I have done to try to curb bottom end damage is running a tiny drivetrain (26/15). I get a few pedal strikes now and again but I don't find the low bb to be a problem.

  5. #5
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    I know it's not drop per se, but I want my BB center to be as close to 12.25" off the ground (with a rigid fork) as possible.

    Pisgah, State College, some parts of Breckenridge... I can't go lower without pedal strikes.


    And I hate pedal strikes more than I hate Bud Light.

    I get it that a bike can "carve" better with a lower BB, but I'm more of a chopper.

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  6. #6
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    My custom frame has 55mm of BB drop (29er) which I requested. I run 180mm cranks, no pedal strike issues unless I try to pedal where I shouldn't which I think is pretty normal.

    I have yet to put my suspension fork on(Fox 34 120mm), which would raise it up even further. I've been thinking about doing it recently, but haven't made a move yet.

    I've ridden two bikes recently that had very low BB's. Both had 70mm drop and 175mm cranks, (also both had gears). I was pedal striking all over. That to me was annoying and scary at times. I should also note that one had B+ tires and the other was a fatbike with a suspension fork. I think the low pressure tires really contributed to the problem.

    Just because your not pedal striking doesn't necessarily mean your not riding aggressively enough IMO. Frankly I think responses should include which pedals are being used by all. Flats have a greater chance of striking IMO. BTW I'm on SPDs.
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  7. #7
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    Good point about the pedals, I think. It probably does make it marginally more intuitive to back pedal when necessary on clipless.

    I'm riding SPDs, too.
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  8. #8
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    I am on Chromag Contact pedals, which are fairly large. I don't remember if riding SPDs a while ago was more likely to have strikes, but it's reasonable to assume that strikes happen more often with big fat flat pedals.

    I encountered this thread and particularly enjoyed this nugget:
    Quote Originally Posted by G-reg View Post
    Folks seem to be talking about pedal strikes like they are some kind of apocalyptic catastrophe. To jack up the BB in order to avoid all pedal strikes is a bit "the nail telling the hammer what to do."

    I'm in the low as practical BB crowd. Why compromise handling 99% of the time just to avoid that 1% where the hammer has remind the nail of it's place.
    yeah, low BBs can feel nice in some situations, but how low is impractical? from a handling standpoint, how high is ideal, all other things being equal? if I could build a bike with some sort of adjustable BB drop from 30 to 70mm and ride a smooth bike park on it, where would I want the BB?

    then there's this:
    Quote Originally Posted by *OneSpeed* View Post
    Just because your not pedal striking doesn't necessarily mean your not riding aggressively enough IMO.
    I think that's what I am getting at. Since someone pointed out to me that high BBs are the bees' knees for this reason, it has me paranoid and riding self-consciously with regard to pedal height. I keep braking before corners and asking "would I have cleaned the hill after it more handily if I didn't brake so hard? why did I brake so hard, what was I afraid of?" if the answer is that I was afraid of hitting a rock and killing my momentum (not to mention my toes, knees, and possibly my face), then would an extra centimeter of clearance make me ore confident?

    I'll do some more research tonight. and my research, I mean ride my bike.

  9. #9
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    Quote Originally Posted by *OneSpeed* View Post

    Just because your not pedal striking doesn't necessarily mean your not riding aggressively enough IMO. Frankly I think responses should include which pedals are being used by all. Flats have a greater chance of striking IMO. BTW I'm on SPDs.
    Possibly but friends I SS with that ride clipless tend to bail and walk stuff where I'll plow thru ratcheting back/forth and grunting it out(5.10s platforms, primarily uphill stuff, downs seem OK), so in the end they get less pedal strikes. I can bail anytime, them not so much tho I think like Yogi Berra said it's 90% half mental.
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  10. #10
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    Quote Originally Posted by socal_jack View Post
    Possibly but friends I SS with that ride clipless tend to bail and walk stuff where I'll plow thru ratcheting back/forth and grunting it out(5.10s platforms, primarily uphill stuff, downs seem OK), so in the end they get less pedal strikes. I can bail anytime, them not so much tho I think like Yogi Berra said it's 90% half mental.
    That's just a level of commitment. When I rode flats, I bailed too early. Now, I tend to grunt it out more with my SPDs.
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  11. #11
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    My displeasure (fear) of pedal strikes comes from eating shit and getting injured. Nothing that required surgery or anything but I was sore for weeks. It leaves an unpleasant impression on your subconscious. I imagine other people have been up-ended by the same thing.

    Examples:
    https://www.youtube.com/watch?v=sAQp...l=DaveMitchell

    https://www.youtube.com/watch?v=OtCr..._channel=oruwu

    skip to 45 seconds
    https://www.youtube.com/watch?v=gTHY...l=JoshGingrich

    You get the idea. Moaning, wheezing, four letter words...

    The other thing that's noteworthy is that I do not notice any decrease in the handling when I ride a bike with a slightly higher BB. (Not that I think 55mm of BB drop is high). In that sense, there's no drawback to having a little buffer.
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  12. #12
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    Singular Hummingbird here, with the EBB set at about 7 o’clock.....

    BB height is around 310mm/12.25” and BB drop is in the region of 38mm/1.5”.

    It suits me down to the ground - we don’t have that much rocky going around here but plenty of ruts and off-camber stuff. I don’t have a problem with pedal strikes but I do ratchet quite a lot (a geared riding mate of mine is always commenting on it....) and instinctively time pedal strokes to clear tree stumps etc.

    It is, I think, one of the overlooked things about singlespeed riding - you get to know exactly how far a pedal stroke will take you, much like when you’re running, really.

  13. #13
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    Quote Originally Posted by Andy R View Post
    Singular Hummingbird here, with the EBB set at about 7 o’clock.....

    BB height is around 310mm/12.25” and BB drop is in the region of 38mm/1.5”.
    interesting. so you have yours almost at the lowest point and it's still only 38mm of drop? that seems quite high.

    I kinda wish I had a EBB frame now so I would experiment. my low BB is low and stable, but the place my riding suffers is in the chunk. not so much from pedal strikes, but from not being able to nimbly hop my bike up ledges and uphill rock gardens. I know that's 99% skill and strength, but I have to wonder if a frame that is not excessively low would help.

    what's the range of adjustment for that EBB? If I remember correctly, the Niner Biocentric II had 8.5mm of adjustment.

  14. #14
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    Some good points shared here.

    Another is that if you ride with a dropper post, and use it, then your BB can be substantially higher without deleterious effects. Reason being that lowering your CoG by several inches with the dropper is *way* more effective than a 5mm change in static BB height.

    All other points about ratcheting and crank length still apply.

  15. #15
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    Quote Originally Posted by mack_turtle View Post
    interesting. so you have yours almost at the lowest point and it's still only 38mm of drop? that seems quite high.

    I kinda wish I had a EBB frame now so I would experiment. my low BB is low and stable, but the place my riding suffers is in the chunk. not so much from pedal strikes, but from not being able to nimbly hop my bike up ledges and uphill rock gardens. I know that's 99% skill and strength, but I have to wonder if a frame that is not excessively low would help.

    what's the range of adjustment for that EBB? If I remember correctly, the Niner Biocentric II had 8.5mm of adjustment.
    I’ve just re-measured and, with the EBB at the 7:30ish position, the BB drop is actually 42mm.
    It’s a Phil Wood EBB insert, so 1/2 inch or 12.7mm of throw.

  16. #16
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    Quote Originally Posted by chuckha62 View Post
    That's just fear of commitment. When I rode flats, I bailed too early. Now, I tend to grunt it out more with my SPDs.
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