I
have noticed that there are different sizes and types of headset
and stem, what are they?
Traditional
headsets fit threaded fork steerers, Aheadsets fit unthreaded
steerers. You can tell which system you have by looking at the
handlebar stem.
Traditional quill stem for bikes with threaded steerers
and headsets |
Aheadstem for bikes with unthreaded steerers and Aheadsets |
When
the fork is threaded, the stem's quill fits inside the steerer.
When the fork is unthreaded, the Aheadstem is clamped over the
unthreaded steerer. Most better-quality mountain bikes and a
growing percentage of road bikes have come Aheadset equipped
since the mid 1990s. Note that headsets and stems made for unthreaded
steerers are not interchangeable with headsets and stems made
for threaded steerers. There are three common sizes.
Standard
or 'one inch' - found on most road bikes and first-generation
mountain bikes.
Fork steerer diameter: 1" (25.4mm).
Aheadstem clamp internal diameter: 1" (25.4mm).
Stem quill diameter: 7/8" (22mm).
Headset locknut is usually 32mm.
Avenger or 'inch and an eighth' - found on
most better quality mountain bikes since the mid 1990s.
Diameter of fork steerer: 1 1/8" (28.6mm).
Aheadstem clamp internal diameter: 1 1/8" (28.6mm).
Stem quill diameter: 25.4mm.
Headset locknut is usually 36mm.
Evolution or 'inch and a quarter'- popular
in the early 1990's, now rarely seen.
Diameter of fork steerer: 1 1/4" (31.8mm).
Aheadstem clamp internal diameter: 1 1/4" (31.8mm).
Stem quill diameter: 28.6mm.
Headset locknut is usually 40mm.
In short, if you need a new headset, stem or fork you'll need
to do some careful measuring. Alternatively, bring the old component
to one of our shops to ensure you get the correct replacement.
Quill stems offer
a little up-and-down height adjustment, but be aware of the
stem's minimum insertion line. This line should be out of sight,
buried in the fork steerer, when fitted.
Aheadstems offer
zero height adjustment. If you feel you're bars are too low,
swap the Aheadstem for a higher
rise one.
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