Wheelchair and scooter bearings are cylindrical housings that allow for free movement of caster wheels, caster forks, rear wheels on manual wheelchairs, motors, gearboxes and some suspension components of power wheelchairs and scooters. In fact, bearings are more prevalent than you might think: the average manual wheelchair has 12 bearings!
Over time, bearings become worn, causing a general deterioration of the wheelchair or scooter part the bearing is attached to. Symptoms can include:
Increased effort to push a wheelchair (or self-propel)
Decreased agility of a manual wheelchair
Squeaks, groans, etc. of manual wheelchairs, power wheelchairs and scooters
Outright failure of the bearing (the bearing breaks apart)
The good news is that in most cases, bearings are easily replaceable. All you need is the size of the bearing, the reference number if available, and the bearing type. Note the example below:
Many bearings found on wheelchairs and scooters have a alpha numeric reference or just a numeric reference number stamped on the side of the bearing which refers to the type and size of the bearing. In most cases, that is all you need to purchase the correct bearing. For alpha numeric reference numbers ending in Z, ZZ, RS, or 2RS, they are all interchangeable (Z and ZZ refer to a metal outer side shield and RS and 2RS refer to a rubber outer side shield protecting the balls inside the bearing). If your bearing has no reference on it, you will have to measure. If the bearing reference appears worn off, you may be able to see it stamped on the other side. You should also note whether the bearing has a flange or snap ring attached to it.
Some points to consider before purchasing (on manual wheelchairs):
Caster wheels: Spin the casters to see if they spin freely - Inspect them closely for hair and other debris that may be caught or wrapped around the axle preventing them from moving freely.
Caster forks: are they straight and even? A bent caster fork can cause the chair to not roll easily or straight. You can also give the chair a shove on even ground - it should roll straight. If not, you may need caster forks instead of bearings. If the caster fork is wobbly, check that it is properly tightened as a loose caster fork can appear to be worn out bearings. Also make sure the dust cap is securely in place (on top of the stem) - this prevents debris and liquids from falling into the stem bearing.
Rear wheels: The wheel itself should roll freely and not wobble. If the wheel is wobbly, check that the axle is secure and not wobbly. Many times a rear wheel with play is down to the axle not being tightened all the way. If you are using quick release axles and the wheel is a bit wobbly, it may just need to be adjusted (most quick release axles have an adjustment under the button to account for excess slack)
Remove the old bearings by pushing a long blunt object into the center of the bearing on one side to push out the bearing on the other side. You can use a screwdriver for this step, however it is recommended to push on the inner race of the bearing (the center part). Turn the caster or wheel over to do the same for the other. For manual or power wheelchair caster fork barrels, you'll have to remove the caster fork first. You can lay the wheelchair on its side (for manual wheelchairs) or prop up the wheelchair (for power wheelchairs). On wheels, there may be a spacer in between the bearings - save for later re-installation. For caster fork barrels, there can be multiple spacers and washers in a certain order which you must note to re-install. Most bearings seat into the space with little effort but some require a gentle pounding to get them in. You only want as much force as necessary to push the bearing in. Two much force can damage the wheel or housing. A rubber mallet works well for this (for casters and wheels, use a cloth or block wood with a cloth on both sides to prevent damage to the caster or wheel). Do one side, re-insert the spacer if you had one before, turn over and repeat. When reinstalling the axle and tightening, take care not to over tighten as this can put undue strain on the bearings. Wheelchair and scooter bearings are all sealed requiring no maintenance or lubrication.