Minimum BB height for MTB?
08-08-20, 08:12 AM
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Minimum BB height for MTB?
Hello, i am designing a bicycle frame for first time. I am making a hardtail trail MTB with 27.5 wheels. What should be the minimum Bottom bracket height?
08-08-20, 09:37 AM
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I made a 29er hardtail with a 70mm BB drop which is considered low for an MTB. But because it's a 29er (big wheels) that works out to about 312mm from the ground to the centre of the BB. The person I was making it for likes a low BB and isn't usually riding on big rocks. He hasn't had any pedal strike issues.
So it depends on the use case but I think quite low makes a nice riding bike.
So it depends on the use case but I think quite low makes a nice riding bike.
08-08-20, 05:50 PM
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Agreed that riding style, suspension presence, crank arm length and other factors come into play. This is one design spec that duplicating what has worked before on a production bike (independent on wheel size) is a good starting dimension. Andy
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08-09-20, 01:26 PM
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Yes although many of us in the real world don't "send it" as much as the designers of production MTBs anticipate. So it's often OK to go a bit lighter gauge on the tubes and a bit lower BB.
08-09-20, 08:21 PM
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Andy.
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08-12-20, 11:45 PM
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I like around 300 to 305mm sagged with 170mm cranks and 130/140mm travel forks. Remember that hardtails change their geometry quite a bit as they go through their travel, unlike full suspension bikes. If you plan to run a long travel fork, the changes are more dramatic than a little XC fork. Keep that in mind as you design the bike.
08-17-20, 09:48 AM
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Recalling Cannondale, still on US soil back then, had a 'Beast Of the East' MTB with a higher than the regular BB.
