ZINN & THE ART OF - VeloPress

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11.9 Loosening and tightening the compression bolt on a threadless headset
5mm
hex key
The shaft of a traditional road bike stem
extends out at an angle of about 73 degrees from
the fork steering tube so that, when installed
on the bike, the shaft is horizontal out to the
handlebar (Figs. 11.1, 11.8). Stems on track
sprint bikes historically tended to be angled
downward when mounted on the bike. Stems
with 90-degree angles and greater, resulting
in an upward angle on the assembled bicycle
(Figs. 11.2–11.5, 11.7, 11.9), are becoming commonplace
on road bikes and even track bikes.
PRO TIP
compression bolt
clamp
bolts
Spacers with Carbon Steering Tubes
If the fork has a carbon steering tube, always
place one spacer above the stem (Figs. 11.5,
11.9). That way, the entire stem clamp is
clamped onto the steerer, and there is no chance
for the upper part of the clamp to pinch the end
of the steerer. This is a good idea for a steel or
aluminum steering tube as well.
If you want to raise the handlebar up high, be
careful about using too many spacers below the
ZINN & THE ART OF ROAD BIKE MAINTENANCE
top cap
spacer
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REMOVE CLAMP-TYPE STEM FROM
THREADLESS STEERING TUBE
1. Loosen the horizontal clamp
bolt(s) (Fig. 11.5) securing the stem
around the steering tube.
LEVEL 1 2. Unscrew the compression
bolt. With a 5mm (usually) hex key,
unscrew and remove the compression bolt
(or “adjusting bolt” because it compresses
the headset into the proper bearing adjust-
stem; consult the owner’s manual for the fork for
recommendations on maximum spacer stack
height. From a strength and stiffness perspective,
it’s preferable to use an up-angled stem, rather
than a level or down-angled one with a lot of spacers
below it. And, of course, make sure the support
plug inside the steering tube (which prevents the
stem clamp from crushing the carbon steering
tube) is supporting the area under the stem clamp.