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Handlebar diameter?

BikeGeek

BrewMonkey
Jul 2, 2001
4,577
277
Hershey, PA
Off the top of your head, is the diameter of a mountain bar the same as a road bar? In other words, can I clamp a road bar in my mountain bike stem without a shim?
 

oldfart

Turbo Monkey
Jul 5, 2001
1,206
24
North Van
Only the new oversize, what is it 31.8? bars and stems are cross compatible with road or mountain bars and stems. Some people use 25.4 stems with road bars, but its not a good fit. The result is often a bar which won't stay put because the there is not a proper amount of surface contact with the bar due to the different sizes, it only fits where it touches. If you're using a light thin wall bar or carbon bar, do you want to risk distorting and potentialy weakening the bar? Not me. I needed a short 1 inch ahead stem for my old Cross bike and got a Profile stiffy. It wouuldn't hold the bar. It kept rotating down. Eventually I stripped out the threads and had to helicoil it. Then the steel bolts broke off. Just not enough surface area in direct contact with the bar.