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When looking at geometry on bike websites some give the BB rise as some figure like -6mm and some give the BB height for example 13.0". I tend to use the latter so how do I convert BB rise to BB height?
Also, just to confirm if I've figured it right, is BB rise the vertical distance of the centre of the BB off an imaginery line drawn between the front and rear dropouts?
Cheers
You're right. Though BB is normally measured as "Drop" from the centreline on mountainbikes. So -6mm would to me suggest a BB above the wheel centres.
So to determine height, measure your wheel radius (or half the diameter) with the tyres you're using, then subtract the BB drop.
Thanks Brant
Basically though converting is never going to be that accurate: given tyre/rim diameter is going to vary between different bikes and I'm taking this info off their websites, its kind of going to be very much guessing as to the wheel radius when trying to to convert.
Yes. If you give BB height, you should really spec the tyre size it's for 🙂