This depends on what bearings in what make model year and engine of car.
how to replace wheel bearings on 2004 GMC envoy?
how do you replace rear wheel bearings on nissan pulsar
Usually the runners can be carefully removed using a thin screwdriver and the bearings should drop out. Replace the bearings and replace the runner by using a 30mm socket or press if you have one.
It would be recommended to replace the rear axle bearings and axles when they are worn/bad. If the bearings and axles are okay, just replace the seals.
Wheel bearings? 4X4 ? 4X2?
There are no replaceable camshaft bearings. You will need to replace the head or heads.
How do you replace the front wheel bearings on a nissan frontier 4x4 1999
Wheel bearings? Axle bearings? Differential carrier bearings? Engine main bearings? Engine rod bearings? Engine cam bearings? Need more info to help you.
When they get noisy.
To replace headset bearings on your bicycle, you will need to first remove the old bearings by loosening the headset and taking out the old bearings. Then, clean the headset and grease the new bearings before installing them. Finally, reassemble the headset and adjust it properly to ensure smooth steering.
Which differential bearings? Pinion bearing? Carrier bearings? End axle bearings?
Front wheel bearings on a 4 wheel drive Explorer are not serviceable, replace them.