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Standard Sizes

BikeGeek

BrewMonkey
Jul 2, 2001
4,577
277
Hershey, PA
I'm looking to upgrade a mtn frame to commuting duties. I've been checking out handlebar options (moustache, etc.) and I'm seeing various sizes in the clamp area. Is there a standard size for a mtn bike stem that I should be looking for? I always thought there was just mtn or road, but now I'm finding all these "grey area" sizes.

Thanks
 

sanjuro

Tube Smuggler
Sep 13, 2004
17,373
0
SF
There are only 3 sizes which are commonly used:

25.4mm: Standard mtn bars
26.0mm: Standard road bars
31.8mm: Oversized bars (mtn and road)

They do make some road bars which fit 25.4, but there are no mtn bars which fit 26.0 stems.

Besides the strength advantages, 31.8 is getting popular with manufacturers because it helps to standardize bar widths with mtn and road.

I know of a few exceptions (like Deda 31.7 O/S measurement). And, of course, Sheldon Brown has a complete explanation of bar diameters:

http://www.sheldonbrown.com/gloss_st-z.html#stem
 

recidivist

Monkey
Aug 29, 2002
283
1
Soquel, Cali
For what it's worth, road and mountain bars and stems (26.0 v 25.4) can be mixed-and-matched, though your mileage (and safety) will vary between different combinations. It's also possible to buy (or make) shims to use MTB bars (25.4) in road stems.

Note that the rest of the bars also have different diameters -- they're designed for either MTB or road brakes/shifters, etc.