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I know that most commonly MTB's use 1 1/8" steerers and older non-suspension bikes use 1" but I don't really know anything about the width of modern road bikes. Do they now use 1 1/8" or do they use a different width?

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up vote 8 down vote accepted

Most modern bicycles, be they road or mountain, use 1 1/8" threadless headsets. You will occasionally find bicycles, particularly in the lower cost ranges, that will still use an old 1" threaded headset and a threaded quill stem, but these are becoming more and more rare every year.

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There are also some oversided headsets (1.5in) used in downhill / freeride mountain bikes. They are not too common outside of this niche. – Benzo Jun 19 '13 at 19:32

Tapered headsets with a larger lower bearing are becoming more common on road bikes. Doesn't make any difference to what stems fit, but if you are replacing a headset (or fork), it matters.


(And 1" threadless headsets also exist. Most likely to be on an older bike that has had a new headset fitted, I suspect.)

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On enduro and DH also, e.g. Trek Slash – Vorac Nov 22 '13 at 9:30

Tapered 1.125/ 1.5 inch head tubes are common on many higher end mountain bikes in 2013 with more bikes and manufacturers heading this way. Most top suspension forks are offered in both straight and tapered steerers. It is possible to use a headset that reduces bottom width in tapered head tubes to a straight 1.125 steerer.

Tapered headsets improve stiffness and strength.

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