Bearings Announce Their Death Long Before They Die

This works through bicycle bearings in the order the parts actually depend on each other.

What a bearing is doing

A bicycle bearing lets one part rotate against another with minimal friction, using balls running between hardened surfaces. Those surfaces are separated by a film of grease, which also excludes water and grit from the contact area. When the grease is displaced or contaminated, the balls run directly on the races and begin to indent them.

Those indentations produce the notchy, rough feeling riders describe, and once present they cannot be polished out. So the entire life of a bearing is a story about whether its grease stayed clean and in place.

Play, the first symptom

Play is movement where there should be none, and it is the easiest fault to detect without removing anything. Check a headset by holding the front brake and rocking the bike forwards and backwards, feeling for a knock at the head tube. Check hubs by grabbing the rim at the top and pushing it side to side, which reveals looseness at the axle.

Mid-traffic, check the bottom bracket by pushing a crank arm towards and away from the frame with the chain off the chainring. On adjustable bearings play is often simply an adjustment; on cartridge units it usually means replacement.

Roughness and grinding

Spin a wheel with the bike lifted and listen, since a healthy hub is nearly silent and a failing one rumbles. Turn the handlebars slowly with the front wheel off the ground, feeling for a notch that pulls the bars towards straight ahead. That notch is an indented headset race and is a common outcome of riding with a loose headset for weeks.

Turn the cranks backwards with the chain removed to isolate bottom bracket feel from drivetrain drag. Roughness without play means the surfaces are already damaged, so replacement is likely rather than adjustment.

Water is the main killer

Most bearings fail from contamination rather than from accumulated rotations, which is why winter commuters replace them more often. Water forced past a seal by road spray or a pressure washer emulsifies the grease and starts corrosion within days.

The headset lower bearing sits directly in the path of everything the front wheel throws upwards, which is why it fails first on so many bikes. Mudguards reduce that exposure substantially, which is one more reason they are the best value accessory on a commuting bike.

Never aim a pressure washer or a strong hose jet at any bearing, since that drives water directly past the seals.

Servicing versus replacing

Loose ball bearings with cup and cone adjustment can be cleaned, regreased and reset, often many times over a bike's life. Cartridge bearings are sealed units, and while some can be prised open and regreased, most are replaced when worn. Replacement usually needs specific tools such as bearing presses or headset cup tools, which is why this is a common shop job.

Catching a bearing at the play stage rather than the roughness stage frequently turns a replacement into an adjustment. Regreasing a hub before winter is cheap insurance on a bike that will spend months in salt spray.

A quick monthly check

Rock the bike with the front brake held, listening and feeling for a knock at the headset. Lift each wheel, spin it, and rock it sideways at the rim to check hub condition and adjustment.

Push both crank arms sideways to check the bottom bracket, then turn them backwards to feel for roughness. Spin the jockey wheels and the pedals, both of which contain bearings that are commonly ignored until they seize. The whole check takes a couple of minutes and catches the faults that turn into expensive ones.

The takeaway

Check for play monthly, because play caught early is an adjustment and play ignored is a new part.

The bike you ride daily beats the better bike you keep indoors.