# Bottom bracket height, demystified



## pretender (Sep 18, 2007)

http://www.belgiumkneewarmers.com/2007/12/how-high.html

_Because races took place on grass, the bicycle’s bottom bracket had to be much higher than that of a traditional road bike so the toe clips wouldn’t drag in the grass—this is a detail the Frogs figured out in the 1950s._


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## Greg Hejtmanek (Aug 17, 2007)

People are all over the place on that one. I have roadbikes, track bikes, road fixies, mtb, cross bikes (probably 18 in all )and pay attention to the BB drops. The ones that ride nicest have low BB heights( (more drop). If you ride slow on a steep bank track clicking a pedal isn't a good thing, so I agree a small drop on a all around track bike is a factor .
In cross I also ride big ass tires which puts the BB height up a little higher anyway. Back in the old days with Lyotard pedals and toeclips high BB was a total necessity. Now with the lower profile pedals not so much. I think 68 is probably IMHO a pretty good average drop.
I did a survey on the web and it seems that American frames seem to have posted between 62-68 mm drop and some of the Belgian frames less than that more like 58-60 ish. Be interesting to see what e-Ritchey thinks. I used to like higher BB on all my bikes, now I am leaning toward more drop. Some of the decision has to do with your riding style and the courses you ride. I think the Belgians ride in conditions that higher BB might work out better. Remember it is freeking cold along the North Sea in winter.


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## 271828 (Jan 22, 2004)

Greg Hejtmanek said:


> I did a survey on the web and it seems that American frames seem to have posted between 62-68 mm drop and some of the Belgian frames less than that more like 58-60 ish.


I tried to do a similar survey. But I've noticed that many manufacturers do not include BB drop on their geometry charts. Is there a way to calculate or estimate BB drop from the geometry charts? Some companies have BB height listed. But since the height of BB depends on what tires you are running, I am not sure if I can get an accurate BB drop from BB height.


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## MIN in PDX (Nov 29, 2007)

BB drop does not depend on your tire choice - BB height does. BB drop is measured by running a line from axel to axel and determining the BB center from this line. That is drop. BB height is the distance from the ground, which is tire dependant. 

I prefer low BB personally. It's much more stable on corners at high speed. My cross bike has a 74mm drop and my track bike is in the 5xmm range and I'd stay I feel much more stable and planted on a high speed corner on my cross bike.


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## Greg Hejtmanek (Aug 17, 2007)

True dat, because as you figured out BB height is dependant on tire size. So I am thinking that it is a wildass guess to get a formula. I would bet a big company like Bianchi, Spec. Kona and Redline spec the bikes with what tire is in stock that day, so the same frame from day to day production could vary a cm or so on BB height. That is why I don't like BB height from the website info. 
I noticed that more and more places mention bar height from center of front wheel to top of bars. That is nice when comparing track to road to cross to mtb positions.


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## MIN in PDX (Nov 29, 2007)

BB height is really relevant for MTBs, in my opinion. BB drop measurement avoids ambiguity with bike-to-bike comparison.


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## zank (Aug 4, 2005)

I like 7 cm.


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## MIN in PDX (Nov 29, 2007)

I like your style Zank. Nice bikes on your site.


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## dead flag blues (Aug 26, 2004)

My next cross bikes will be customs, and i'll leave it up to the builder(s). I think my latest inclination is to keep the bb drop a tad lower..


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## MIN in PDX (Nov 29, 2007)

I like your style Zank. Nice bikes on your site.


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