AI quick summary
- Most cartridge bearings fail from water ingress and grease wash-out, not load — good seals and fresh grease do more for lifespan than any upgrade kit
- Hub bearings need the most frequent service in wet climates: a year-round commuter ridden through rain should have hub bearings serviced or replaced every 6–12 months
- Headset bearings fail from brinelling under impact (potholes, crashes) more than from rotation wear — replace when the steering feels indexed or notched, not just gritty
- Use a marine-grade or lithium-complex bicycle grease for steel bearings; avoid thick automotive NLGI-2 grease in low-torque bearings like jockey wheels and pedal bodies, where it causes drag
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Service intervals by location
Realistic service and replacement intervals for bearings on a bike ridden year-round in a wet temperate climate. Dry-climate or summer-only riders can roughly double these.
| Bearing location | Service interval | Replacement interval |
|---|---|---|
| Hub (rear, drive side first) | 6–12 months | 2–4 years |
| Hub (front) | 12 months | 3–5 years |
| Headset | 12 months (regrease seals) | 2–4 years or after a crash |
| Bottom bracket (cartridge) | not serviceable | 2–4 years |
| Pedal | 12 months | 3–5 years |
| Jockey wheels (derailleur) | 12 months | when noisy or visibly worn |
/ 02
Symptoms by location
Each bearing on a bike has its own failure signature. A hub bearing goes rough first under load — usually the drive-side rear, because it carries the most weight and the most sealing surface — and is felt as a vibration in the pedals rather than heard. Lift the rear wheel, spin the cranks, and grab the chainstay: a rough hub transmits a buzz through the frame that a smooth hub does not.
A headset bearing announces itself through the handlebars. The first sign is a faint dry scratching when sweeping the bars side to side off the bike; the second, more advanced sign is indexing — a clear detent every few degrees. A bottom bracket goes rough with a click or creak on every pedal stroke, often only under load and not on the stand. A pedal bearing announces itself with a click under power, almost always the left pedal first because it receives more off-centre load.
/ 03
Grease: which one and how much
Bearing grease is not all the same. The relevant properties are base oil viscosity, thickener type, and water resistance. For steel cartridge bearings on a bike — hubs, headset, bottom bracket — a lithium-complex grease with NLGI consistency 2 (Park Tool PPL-2, Phil Wood, Finish Line Premium) is the universal choice. It has good water washout resistance, stable viscosity across the temperatures a bike sees, and is compatible with the rubber seals used on cartridge bearings.
Marine grease (waterproof, calcium-sulfonate based) is the right call for hubs ridden through winter rain or for any bearing regularly submerged. Avoid automotive wheel-bearing grease — it is formulated for much higher temperatures and loads, and its tackifiers can make small bearings feel sluggish. For low-torque bearings (jockey wheels, some pedal bodies) a lighter oil or low-NLGI grease produces less drag and is more appropriate.
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When to replace vs service
Cartridge bearings are sealed units — when they feel rough, you either replace them or, in the case of serviceable ones (rare on modern bikes), carefully pry out the seal, flush with solvent, repack with grease, and re-seat the seal. Servicing a sealed cartridge bearing buys you months, not years, and is usually a stopgap until a replacement arrives.
Replace when: the bearing feels notched (brinelled), the seal is damaged or missing, you can feel play when the bearing is unloaded, or there is visible rust weeping from the seal. Service only — by cleaning, regreasing, and resealing — when the bearing still spins smoothly but has begun to sound dry. A bearing that has been run rough for more than a few hundred kilometres is past service; the races are already damaged.
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