# Ways to help increase BB height?



## sandyeggo (Mar 6, 2011)

The BB on my geared bike (11 Cannondale Flash) is significantly lower than my SS bike (11 Cannondale Trail SL3) -- to the point where I can put them side-by-side and the pedal of the Flash will easily fit underneath the pedal of the Trail. As a consequence, I have an issue with pedal strikes on the Flash. I really love the Flash (light, fast, responsive) and until I started riding the SS, the pedal strikes were just annoying. With the Trail, I don't even think about pedal strikes but when I get back and ride the Flash it seems all I do is worry about pedal strikes which makes riding it not as fun for me as it should be. 

Any ideas to "increase" the BB height (or reduce pedal strikes)? Ideas that come to me are taller tires (not sure if there are any that would really make a difference) and/or shorter cranks (not sure that would make that much of a difference either). 

Any thoughts would be appreciated. Thanks!


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## jtrops (Aug 4, 2008)

What fork do you have? How much travel, how much sag? According to the Cannondale site the Flash has a higher BB by about 2/10". Are you running the fork on your flash on the soft side? 

The only thing that would bring your BB up without screwing the GEO, would be shorter cranks and fatter tires (F+R). If you add quite a bit of fork length it will raise the BB, but not without changing the GEO. 

From my experience changing cranks from 175 to 170 makes a difference with pedal strikes, so it could be worth it.


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## whoda*huck (Feb 12, 2005)

jtrops said:


> What fork do you have? How much travel, how much sag? According to the Cannondale site the Flash has a higher BB by about 2/10". Are you running the fork on your flash on the soft side?
> 
> The only thing that would bring your BB up without screwing the GEO, would be shorter cranks and fatter tires (F+R). If you add quite a bit of fork length it will raise the BB, but not without changing the GEO.
> 
> From my experience changing cranks from 175 to 170 makes a difference with pedal strikes, so it could be worth it.


Shorter cranks does not raise the BB height. It will lessen pedal strikes, but you pay for that with less leverage/power with each pedal stroke. 
OP, these days bikes are being designed with lower bottom brackets to give you a more "in the bike" instead of "on the bike" feeling. Have you measured the actual BB height of each bike?


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## was98strat (Jul 10, 2007)

reducing pedal strikes is easy...stop pedaling through your turns!!! the only way to increase the BB height is to physically raise it, The only way to do that is to use longer travel forks, or reduce the sag on the front for. Either one will change your geometry.


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## net wurker (Sep 13, 2007)

I don't know if your frame/fork will handle it or not, but a 650b wheelset/tires would give you an extra 3/4" pedal clearance. Not a cheap option, though.


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## net wurker (Sep 13, 2007)

Pedal strikes can happen in rock gardens, too, where 'not pedaling' isn't always an option.


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## theMeat (Jan 5, 2010)

Bigger wheels, bigger tires, shorter cranks or shorter pedals will all help.


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## Guerdonian (Sep 4, 2008)

whodaphuck said:


> Shorter cranks does not raise the BB height. It will lessen pedal strikes, but you pay for that with less leverage/power with each pedal stroke.
> OP, these days bikes are being designed with lower bottom brackets to give you a more "in the bike" instead of "on the bike" feeling.


+1 to what he said


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## AndrwSwitch (Nov 8, 2007)

Shorter cranks will help.

Actually not an issue with power output over time. People tend to adjust to it, and develop about the same power they did before at any given effort.

I think with mountain bikes, it can be helpful to be in a higher gear in order to use a smaller angle of rotation at the pedals to pop up the front wheel. That's the only real problem I see with shorter cranks. Although there's some counter-intuitive stuff with shorter cranks - some people find they can push the same, or even a taller gear, efficiently, because their feet don't have to travel around as big a circle. If that applies to you, there'd be no handling downside.

Pez Cycling looked over a few different studies last year and did a writeup.
Crank Length - Does Size Really Matter?

One of their conclusions was that since effects of changing crank arm length are pretty minor and go away with a little practice on the new size, using shorter cranks to get more ground clearance doesn't have much in the way of downsides. If you have access to an academic library, following the references back might be of some interest. The methods definitely leave something to be desired, but it's extremely difficult to test anything to do with endurance sports well.


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## sandyeggo (Mar 6, 2011)

First of all, thanks for all the responses! LOVE this forum!



jtrops said:


> What fork do you have? How much travel, how much sag? According to the Cannondale site the Flash has a higher BB by about 2/10". Are you running the fork on your flash on the soft side?
> 
> The only thing that would bring your BB up without screwing the GEO, would be shorter cranks and fatter tires (F+R). If you add quite a bit of fork length it will raise the BB, but not without changing the GEO.
> 
> From my experience changing cranks from 175 to 170 makes a difference with pedal strikes, so it could be worth it.


Its the Lefty PBR. LBS set it for my weight. I have no idea how much sag there is when i'm not on it, but the pedals of the Flash slide right under the pedals on the Trail when unweighted. 
I looked on C'Dale website and the Flash 29er and Trail 3r (or whatever the SS is for 2012) have identical BB heights. I could have sworn that both cranks were the same on my two bikes (I'll have to check when I am done with work). If that's true, that leaves only sag and the types of tires that make the difference? On the Flash I'm running Kenda Slant 6's and on the Trail I'm running Mountain Kings. Can tires make that much difference? If I recall, we're talking about the Flash pedals being a good inch closer to the ground.

Any recommendations for a "tall" tire?



AndrwSwitch said:


> Shorter cranks will help.
> 
> Actually not an issue with power output over time. People tend to adjust to it, and develop about the same power they did before at any given effort.
> 
> ...


I might try shorter cranks. I'm not racing or anything so losing some efficiency doesn't bother me -- I'd rather be comfortable with bike and how it handles vs. having the most efficient machine out there.

I really hope to make it work because otherwise it is a fun bike. Probably the best alternative of them all is to just get on it and ride -- hopefully I'll just get used to it/learn better technique/learn to time pedal strokes and get past the mental issue.


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## mimi1885 (Aug 12, 2006)

Avoid pedaling in the rock garden with your XC HT. If you try to make adjustment and raise BB on the flash you'd loose the corner on rail, responsive trade of the Flash. I think right tool for the right job, try some AM HT or time your pedal better. 

I have similar problem with my Mojo but I would not want to trade the handling for that however I did put 650b front wheel to relax the HA a bit it suited me perfectly.


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## zebrahum (Jun 29, 2005)

Canfield Crampon pedals will give you additional pedal clearance. Doesn't seem like much on paper, but it's significant.


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## AKamp (Jan 26, 2004)

Not sure what cranks you are running but you could try a bb eccentric if it will fit your frame.


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