What benefit does a high bottom bracket provide?- Mtbr.com
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  1. #1
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    What benefit does a high bottom bracket provide?

    I'm learning about how different geo numbers behave on the trail, but I have yet to hear of any reason why a higher vs a lower bottom bracket height would be preferred. The only exception is pedal strikes, but then why not lower the otherwise high BB a bit lower to benefit from the lower COG while cornering?

    At the moment I am thinking that it is simply a limitation on the bike that does this.

    This came up from reading comments on the Pivot 429 carbon BB being too high while a burly bike like the Stumpjumper FSR is known for having a low BB height. What is going on there?

  2. #2
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    It really depends on how you are riding the bike. A higher BB lets you get over logs without getting stuck on your chainring/bashguard and gives you fewer pedal strikes. So if you are riding where rocks, logs and big roots are everywhere then a higher BB makes sense. I ride on the East Coast, and a higher BB is definitely a benefit. If your trails are smoother, then it makes more sense to have a lower BB for better handling. I have rode in the midwest in Ohio and Indiana and I prefer a lower BB for those trails because they were smoother and twistier.
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  3. #3
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    +)Good for clearing obstacles.

    -) less stable at speed.

  4. #4
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    I have a 14.1 inch BB on my kona. Its really fun for going slow over obstacles. Its not fun for going fast or flicking the bike around. All in all, id rather have a lower bb again.

  5. #5
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    Thanks guys. Makes sense. Sounds like in my case lower bottom bracket is where it is at being that I'm in SoCal.

    I ride a stumpjumper and so far I have not had any pedal strikes and only had a few on my spearfish before adjusting.

  6. #6
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    Quote Originally Posted by Art.C View Post
    I'm learning about how different geo numbers behave on the trail, but I have yet to hear of any reason why a higher vs a lower bottom bracket height would be preferred. The only exception is pedal strikes, but then why not lower the otherwise high BB a bit lower to benefit from the lower COG while cornering?

    At the moment I am thinking that it is simply a limitation on the bike that does this.

    This came up from reading comments on the Pivot 429 carbon BB being too high while a burly bike like the Stumpjumper FSR is known for having a low BB height. What is going on there?
    My custom rigid/hardtail bikes have ~13" BB hts. Do not care for BBs under about 12.25". I want the pedal and chainring/bash clearance, plus I find a higher BB to be more flickable and responsive to body english. Stability at speed has not been an issue.

    Ruts, rocks, logs, roots, narrow side slope trails--up and down. Have caught the bash on roots, rocks and logs. Whacked pedals on the same plus the ground in ruts and side slopes, sometimes even with the pedals level.

    Some of the worst is grounding a pedal while climbing techy trails. Was on a 4" travel fully with an unsagged BB ht of 12.7". Missed a lot of climbs because of pedal strikes.
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  7. #7
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    what shiggy said.

    pretty interesting this came up as i've been messing with my bikes lately.
    i'm coming off a vassago jabberwocky - low bb, a bunch of bb drop (29'r)

    i'm currently riding a 26" wheel bike that had a fairly high bb to start with. I put a f29 (fox 29'r fork) that i had laying around on it.

    what i've found is really interesting and a lot of fun for our tighter, twisty, flowy trails:
    the longer fork lifts the bb even more (but just a hair) but it also rakes the front end out a bit.
    the end result is a bike that's flickable as hell (or goes edge to edge faster as i like to say) but steers a hair slower than before so its not nervous as a cornered rat.

    i'm diggin it.......would love to hear what you guys think of it.......

  8. #8
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    Adding: I have a custom frame with an EBB that I run geared. When I first set it up I ran the EBB "down", putting the BB ht ~12.2".

    Rode it for about a week and it was just not quite right. Felt dead, sluggish.

    Rotated the EBB to the "top" position, which raised the BB 1/2". Raised the saddle and the bars the same amount. No other changes.

    On the next ride the bike came alive. Light, responsive and fun.
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  9. #9
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    Quote Originally Posted by Art.C View Post

    This came up from reading comments on the Pivot 429 carbon BB being too high while a burly bike like the Stumpjumper FSR is known for having a low BB height. What is going on there?
    DW-Link geometry, the bb is actually pretty low if not the lowest of the full suspension design, because when you accelerate the bb height does not change after sag. Also promote more corner-like-it's-on-rail sensation too.

  10. #10
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    In it and On it

    Ever hear a rider describe a frame as being in it or on it?

    I have learned an in it frame means a lower bottom bracket. You feel inside the frame and you can rail into corners.

    An on it frame means you have a higher bottom bracket. Yea, you can rail into corners, but you have an on the top feeling.

    I prefer lower bottom bracket frames ... and I can really notice it all other things being equal.

    An on it frame

  11. #11
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    I have heard that several times, especially in reviews of early 29'er bikes.

    Thanks

  12. #12
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    I have bikes with high and low BB and I prefer the high BB so i don't have to worry all the time about pedal strikes. Having that extra BB height has been nicer on the trails. I also like feeling "on" the bike vs. in it for some reason.

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