AI 速览
- A rear hub that clicks under load almost always has a worn drive-side bearing — not a freehub problem.
- Press bearings in squarely contacting only the outer race — hammering on the inner race brinells the balls instantly.
- DT Swiss Star Ratchet hubs use 6903 bearings; Hope Pro 4 uses 6803 — never assume one size fits all.
- Axle torque matters as much as preload: a 12 N·m thru-axle and 40 N·m locknut are typical trail-hub specs.
/ 01
Symptoms and diagnosis
Three sounds mean hub bearings are dying. A dry click under hard pedaling is a pitted drive-side ball surface. A constant rumble when you spin the wheel off the bike is a dry non-drive bearing. And a notchy feel when you turn the axle by hand — like rolling over gravel — means the grease is gone and the cage is failing.
Pull the freehub and axle, wipe the bearings, and check for play. Anything more than about 0.05mm of radial play you can feel with your fingers is a write-off. Don't bother re-greasing sealed bearings — by the time you can feel it, the balls have brinelled the races.
/ 02
Tools required
Hub bearing service kit
| Tool | Purpose | Notes |
|---|---|---|
| Bearing press (Park HHP-3) | Square install | Use with 1/2" rod |
| Brass drift punch | Drive out old bearing | Brass, not steel |
| Dead-blow mallet | Striking drift | Avoid steel hammer |
| Calipers (0-150mm) | Bearing ID/OD check | Digital preferred |
| Waterproof grease | Shell bore lube | Phil Wood or marine |
/ 03
Identifying the right bearing
Pop the seals gently with a pick and read the number printed on the rubber. 6803 (17x26x5mm) is the most common 12mm-axle bearing, used in DT Swiss 350 and Hope Pro 4. 6903 (17x30x7mm) is the workhorse for 15mm thru-axle fronts. 15267 and 15268 are the oversized Shimano designs for XTR cup-and-cone hubs. Never substitute — the inner diameter, outer diameter, and width all have to match the hub shell.
/ 04
Removal: protect the shell
Drift out from the opposite side. Tap alternately at 12, 3, 6, and 9 o'clock — never walk the bearing out by hammering one spot. The shell will ovalize and the new bearing won't seat. If a bearing is seized, a heat gun on the shell (not the bearing) to about 80°C breaks the corrosion bond without distorting anything.
/ 05
Installation: press and preload
Grease the bore. Press the new bearing in by contacting only the OUTER race — driving on the inner race brinells the balls against the race instantly. The Park HHP-3 with the right adapters costs about $130 and pays for itself on the second hub. Seat until flush, no further — over-pressing loads the bearing axially and shortens its life.
Preload varies by hub design. Star-ratchet DT Swiss hubs use only the wave washer under the end cap — no user adjustment. Hope hubs use a 17mm adjustable nut. Chris King sets preload at the factory and you don't touch it. Cup-and-cone Shimano needs the classic cone-plus-locknut dance.
/ 06
Hub-specific torque
Common hub torque and preload specs
| Hub | Preload | Axle torque |
|---|---|---|
| DT Swiss 350 / 240 | Wave washer only | 8 N·m end cap |
| Hope Pro 4 / Pro 5 | Adjustable 17mm nut | 40 N·m locknut |
| Chris King R45 | Factory-set collar | Do not adjust |
| Shimano XTR cup/cone | Cone + locknut | 35-50 N·m axle |
| Industry Nine Torch | Adjustable end cap | 6-8 N·m |
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