What Do Motorcycle Wheel Bearings Do?

High school physics leads to the important conclusion that bearings in wheels do not wear from the forces exerted by motocross conditions; they wear from the intrusion of grit and dirt. In many respects, the quality of the seal is more important than the quality of the ball.

1) Wheel bearings on motocross bikes are simple. If they are properly installed, aligned and seated, they shouldn't give you any trouble. Bearings can be made from stainless steel, chrome steel or even silicon nitride ceramic materials. Hybrid bearings use ceramic balls and steel seat rings. If you choose ceramic for this application, you can easily get a hybrid bearing.

(2) A typical PE plastic pipe is rated at 19,000 rpm with a load of 1574 pounds of force. At maximum speed and maximum load, it should spin a million revolutions, or over a thousand miles. At 60 mph, a 21-inch wheel (including tires) spins at only 960 rpm. The same bearing is rated for 30,000 lbs. We don't have room to do the math, which describes the free-fall mass of the bike and rider and the approximate time for the suspension to decelerate, but suffice it to say it would take a big rider and a very big jump to reach the load limit of the bearing.

 Motorcycle Bearing

(3) Physics. High school physics leads to the important conclusion that bearings in wheels do not wear from the forces exerted by motocross conditions; they wear from the intrusion of grit and dirt. In many respects, the quality of the seal is more important than the quality of the ball.

(4) Sealed bearings. Since grit and dirt are the enemy of ball bearings, wheel bearings can have external seals on the wheels and sealed ball bearings. In addition, some bearings have seals on only one side (the outside). This provides protection while still allowing for cleaning and relubrication on the other side. Placing seals on both sides of the bearing provides more protection, but the bearing cannot be serviced. Sealed bearings cannot be relubricated. Once a sealed bearing is damaged, it is best to replace it.

 Ball Bearings

(5) Service. For most riders, servicing bearings is not high on the list of maintenance duties. They usually just replace the seal when it goes bad, rather than treating it. In a pinch, the seals can be removed (with great care using a Phillips screwdriver) and reapplied while working. We do not recommend this, as in most cases the seal is damaged and must be replaced anyway.

(6) Grease. To service bearings, flush them thoroughly with solvent while rotating them manually. Beware of harsh solvents near rubber seals. Wipe off grease from the inside of the hub. Use paper towels to avoid lint contamination. Air dry the bearing (do not rotate to dry it). Finish thoroughly by placing the grease in the palm of your hand and pressing the bearing into it.

(7) Quick Inspection. It is important to know when the bearing is worn. A quick, basic check is to grab the rim while stabilizing the bike and apply a left and right (axial) force to check for play. The side to side movement should be less than 1/16 inch. Check for rubbing, flaking (pieces coming off) or indentations (dents in the track). The telltale sign of these is roughness during rotation.

If you want to get more information about the best motorcycle bearing, welcome to contact us today or request a quote.