Bearings on a bike: where are they?
A bike contains between 10 and 20 bearings depending on its complexity. Each rotates around an axle and reduces friction. When they wear out, you'll feel play, grinding, or pedaling resistance.
Headset
Two bearings between the frame and fork. It's the first to suffer because it absorbs all frontal impacts. Symptoms: play when braking hard (the fork "knocks"), grinding when turning the handlebars, a notch at center.
- Common type: sealed cartridge bearings press-fit into cups. Standards: 1"1/8 (standard), 1.5" (tapered steerer), ZS44/ZS56 (zero-stack)
- Service interval: every 6 months or 3000 km in dry conditions. More often in rain or MTB use
- Maintenance: remove stem and fork, extract bearings, clean with degreaser, inspect balls and races. If the races are pitted (brinelling), replace. Otherwise, regrease generously and reassemble
Bottom bracket (BB)
Two bearings supporting the crankset axle. They handle all pedaling power, mud, and water running down the seat tube.
- Types: BSA threaded (68/73 mm), press-fit (BB86, BB92, PF30, BB30), T47 (large-diameter threaded)
- Interval: every 6-12 months depending on usage. In winter MTB, every 3 months
- Wear symptoms: clicking when pedaling, lateral play in the cranks, grinding
- Maintenance: extraction with the right tool (BSA wrench, press-fit remover), cleaning, bearing inspection. On a BSA, you can often just regrease the threads and bearings. On press-fit, replacement is often simpler
Hubs
Two bearings per hub (front and rear), sometimes four on high-end hubs. The rear hub also contains the freehub mechanism (pawls or ratchet).
- Cup-and-cone: classic Shimano system. Loose balls in a machined race. Adjustable and durable, but requires precise adjustment with two flat wrenches (13/15 mm most commonly). Tighten the cone until play disappears, then lock the locknut. If you feel a tight spot, you've over-tightened
- Sealed bearings: no adjustment possible. When worn, you replace them. Removal with a press or bearing puller
- Interval: check for play every 3 months. Regrease cup-and-cone once a year. Replace sealed bearings every 1-2 years
Pedals
Two bearings per pedal (often one needle bearing + one ball bearing). Access is usually straightforward: unscrew the axle cap, extract the axle, clean, regrease.
- Interval: once a year. More often if you ride in the rain
- Tip: the left pedal has reverse threading (unscrews clockwise)
Jockey wheels (derailleur pulleys)
Two small bearings (often plastic bushings on entry-level, sealed bearings on high-end). They wear quickly because they sit in the dirty chain path.
- Interval: check every 2000 km. Replace plastic bushings when they develop play
- Maintenance: soak in degreaser, dry, one drop of oil on the bushings
Which grease to use?
- Lithium grease: versatile, affordable, suitable for 90% of bike bearings. Examples: Park Tool PolyLube, Finish Line Premium
- Marine grease: water-resistant, ideal for headsets and hubs in wet conditions. Thicker, slight rolling resistance
- Ceramic grease: for high-end ceramic bearings. Pointless on standard steel bearings
Golden rule: too much grease is better than not enough. Excess will be expelled naturally. A dry bearing is a dead bearing.
