Any disadvantages of low BB besides climbing?- Mtbr.com
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  1. #1
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    Any disadvantages of low BB besides climbing?

    Are there any other obvious disadvantages of a low bottom bracket other than climbing and possibly clipping cranks on the way down? DH bikes are still around 340mm but with 200mm of travel what could actual bb height be? I only ask as the new evil insurgent in x-low is really low... Cheers

    edit: found some other stuff regarding this online so all good thanks!
    Last edited by BakerFitness; 10-06-2015 at 02:05 AM.

  2. #2
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    For me....the pedal strikes while pedaling through really rocky sections, especially uphill and flats next. DH- less of an issue.

  3. #3
    jrm
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    The key is the 15 to 17mm sag they suggest. So in the lowest position with a 150mm your resulting BB height is somewhere around ~12.4 to 12.3~which isn't that low. If want a higher sagged BB ie: ~12.66-12.7~ then consider using a 160mm fork. IN the end your riding style will adjust to the lower CoG. Not to mention the bike will handle better...

  4. #4
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    A lower BB is less ground clearance. In particularly rocky technical terrain (think northern New England), a lower BB means more rock strikes - to your chainring/bashguard and not just pedals. If you're crawling up and over sharp pointy rocks, a super-low BB is a real PITA. This consideration isn't applicable everywhere, obviously.

  5. #5
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    Quote Originally Posted by Stripes View Post
    No, learn to ratchet the cranks and that will help you with the pedally technical stuff.
    No, there are times where ratcheting isn't an option and momentum is needed. Pedal strikes are going to happen, whether you know how to ratchet your cranks or not. They will happen more frequently with a lower bottom bracket. People that say "just ratchet" haven't ridden much technical pedally stuff, in my experience.

  6. #6
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    Its not just pedal strikes. I had a 12.9bb xc bike and it would scrape the frame/bb itself. I really enjoy low speed rock crawling, going up and down. Taking the silly bad line off in the corner just to see if I can clear it. I have a 14.5 inch BB bike, and not much is off limits. My 12.9 inch bb bike was really no fun at all to do that on. Its only an inch and a half on paper, but man that makes an enormous difference.

  7. #7
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    Harder to lift the front.

  8. #8
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    More in the bike feel, more planted, which some people find is less desirable than an agile bike that floats. Reduces the lean angle that prevents you from pedaling too, especially if you have long feet and have a mid-foot over axle foot placement. If you're used to a road bike or HT (not too uncommon to see 300mm/11.8"), a FS with 330mm/13" BB shouldn't need much adjustment. Pedal strikes tend to mainly happen in the new-to-you bike adjustment phase, then becoming as rare as any other bike.

  9. #9
    LMN
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    1. Obviously pedal strikes.
    2. Makes your front end effectively higher. (May or may not be an issue).
    3. In theory at least, a bit harder to get the front end up.

    Not many disadvantages.

    The pedal strikes can be easily fixed by shorter cranks. You give up a bit of mechanical advantage with shorter cranks but that can be adjusted for by changing your gearing.
    "The best pace is suicide pace, and today is a good day to die." Steve Prefontaine

  10. #10
    dwt
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    Any disadvantages of low BB besides climbing?

    Quote Originally Posted by mountainbiker24 View Post
    No, there are times where ratcheting isn't an option and momentum is needed. Pedal strikes are going to happen, whether you know how to ratchet your cranks or not. They will happen more frequently with a lower bottom bracket. People that say "just ratchet" haven't ridden much technical pedally stuff, in my experience.
    +1. The "ratchet the pedals" people are just like the "flow" people. The truth is that they don't ride technical terrain or if they do they ride it slow.


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  11. #11
    dwt
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    Quote Originally Posted by One Pivot View Post
    Its not just pedal strikes. I had a 12.9bb xc bike and it would scrape the frame/bb itself. I really enjoy low speed rock crawling, going up and down. Taking the silly bad line off in the corner just to see if I can clear it. I have a 14.5 inch BB bike, and not much is off limits. My 12.9 inch bb bike was really no fun at all to do that on. Its only an inch and a half on paper, but man that makes an enormous difference.
    I'm in agreement, though rocks, logs, etc. will hit your chainring(s) before the bb. Scraping your chainring messes up your balance & impedes forward movement of your bike. So I use chainrings 34t or less. I like the same sort of terrain, but fast as I can do it. Where if you don't ride tubeless, you constantly risk front pinch flats.


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  12. #12
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    I noticed the additional pedal/crank end strikes immediately.
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