AI 速览
- Integrated (IS) headsets use drop-in cartridge bearings — the most common type on modern road and gravel bikes, identifiable by the 36° bearing seat machined directly into the head tube
- Indexing — a notched, detent feel when turning the bars — means the bearings are brinelled from impact and must be replaced, not adjusted; tightening the top cap on indexed bearings just accelerates the damage
- Set preload with the stem bolts loose: turn the top cap bolt until all play disappears with no binding, then torque the stem bolts to 5–6 Nm on a carbon steerer
- Re-grease the bearing seals annually in wet climates; a full bearing swap is typically needed every 2–4 years depending on mileage and weather exposure
/ 01
Headset types you will meet
The four headset families and where each one is found. The code (EC, ZS, IS) follows the SHIS standard.
| Type | SHIS code | Bearing style | Where you will find it |
|---|---|---|---|
| Threaded | — | Loose ball or cage | Vintage road, low-end commuters |
| External cup | EC34, EC44 | 1-1/8" cartridge, pressed into cup | Older road and early MTB |
| Zero-stack (semi-integrated) | ZS44, ZS56 | Cartridge pressed into the head tube | Modern MTB, some gravel |
| Integrated | IS42, IS52 | Drop-in cartridge (e.g. 41.8×6.5) | Most modern road and gravel |
/ 02
Symptoms it needs service
There are three failure modes, and each points to a different fix. The first is a faint dry scratching when turning the bars — the bearings still have life but the grease is gone; remove, clean, regrease, reinstall. The second is indexing: a clear detent or notch every few degrees of rotation. The bearing races have brinelled — small dents where the balls sit under load — and the bearing is dead. Adjustment will not help.
The third is play: a small click when the front wheel is rocked back and forth with the front brake locked. This usually means the top cap preload has loosened. Snug it up with the stem bolts backed off, then re-torque the stem. If play returns within a ride or two after re-preloading, the bearings are worn and the stem is no longer clamping true — replace them.
/ 03
Bearing replacement
Removing an integrated headset bearing is a job for a bearing drift or a flat-blade screwdriver tapped gently around the inner race — drive it down and out through the head tube. The bearing seat in an IS frame is a 36° chamfer; the new bearing drops in by hand and is seated by tapping the inner race gently with a soft mallet, or by installing the fork and snugging the top cap to draw it home.
Always match the bearing code exactly. Common sizes include 41.8×6.5 (Campagnolo/standard road IS), 41.8×7 (FSA), and 47×7 (some gravel). The diameter and height differ by fractions of a millimetre but the difference between a correct fit and a loose one is exactly that fraction. Take the old bearing to the shop; do not guess from the frame model year.
/ 04
Adjusting preload properly
The most common mistake is cranking the top cap bolt with the stem already tight. The top cap exists only to set bearing preload before the stem is clamped; once the stem is torqued, the top cap carries no load and can be removed entirely. Sequence: loosen stem bolts, snug top cap bolt until all play disappears but the bars still turn freely with no notchiness, then torque the stem bolts to spec (5–6 Nm on a carbon steerer, 6–8 Nm on alloy).
On a carbon steerer, never exceed the maximum spacer stack printed on the steerer or in the fork manual — usually 30 mm total above the headset top cover. More than that and the steerer can crack at the top clamp under load. If the stem is sitting high on spacers, cut the steerer or flip the stem before adding more.
/ 来源