Bearings

BMX bearings: the wear part that decides how a wheel rolls

A bearing costs a fraction of the price of a hub and yet dictates all of its smoothness. On a race bike exposed to dust, mud and the pressure washer it is a consumable, no differently from a brake pad or a chain. Replacing it in time avoids damaging the seat in the hub shell, a far more expensive repair.

Sealed ball bearings: reading a reference

BMX race hubs use cartridge ball bearings with rubber seals, identified by a code such as 6902-2RS or 15267-2RS. The 2RS suffix means two rubber seals, the standard protection for outdoor use. The digits encode inner diameter, outer diameter and width: all three dimensions must be matched exactly, and a bearing with the same bore but a different width will not fit.

Finding the right reference

Three methods, in order of reliability. The reference is usually etched on the face of the worn bearing: that is the safest source. Failing that, measure inner diameter, outer diameter and width with a vernier caliper. Finally, many manufacturers publish the bearing list for each model of BMX hub. If in doubt, send us the exact brand and model of the hub rather than ordering on axle diameter alone.

Compatibility by axle diameter

• 10 mm axle: 10 mm bore, the most common fitment front and rear.
• 15 mm axle: 15 mm bore, on the front hubs of recent forks.
• 20 mm axle: 20 mm bore, on through-axle hubs.

Axle diameter gives you the bore, but nothing else: two 10 mm hubs can call for two different references depending on shell width and the type of cassette driver fitted.

Washers, spacers and build clearance

Washers and spacers are not accessories: they set the distance between bearings and the load on the cones, and therefore the preload. A missing or under-length spacer leaves side play that will destroy a new bearing within a few sessions. Always reassemble in the same order with the same parts, and replace a marked or distorted washer at the same time as the bearing.

When to replace, and why not to wait

• Side play: the wheel moves left to right once the axle is tightened.
• Noise: rasping, crackling or a grinding sound at low rotation speed.
• Rotation that catches: the wheel no longer spins freely, or stops in steps.
• After a pressure wash or a wet season, even with no clear symptom.

A seized bearing ends up turning in its seat and wearing the bore of the hub: at that point it is the hub that needs replacing.

The brands we stock

Pride supplies the original bearings for its front and rear hubs, referenced by model. Excess offers the bearings and washers matching its own hubs and several very widely used standards. Stealth covers its 20 mm axle builds. For hubs from other brands, standard references cover the vast majority of cases, provided all three dimensions are confirmed.

Servicing and removal

A 2RS bearing needs little maintenance, but degreasing it in solvent strips the factory grease and shortens its life: clean the outside, not the inside. Removal is done with a drift or puller pushing on the outer race, never on the seals. On refitting, lightly grease the seat to make the next removal easier, and check the tension of your spokes while the wheel is apart.

The BMX RACING advice

Send us the etched reference, or the brand and model of your hub: we identify the bearing, the matching washers and the quantity needed for the complete wheel. Dispatched within 24 to 72 hours, you can spread the cost over 2 or 3 payments.