Dear Tom and Ray: My brother-in-law, Sam, thinks our wheel bearings are "going bad" on the right rear. My husband, James, and I don't hear any noises that would suggest a problem. But ever since Sam put the idea into James' head, he's been set on fixing it. We've done fairly simple repairs ourselves in the past, but I don't think we should do this one, for two reasons: (1) I'm not convinced there's anything wrong, and (2) it's too complicated to perform by ourselves with no experience at all in this area. My question: How do we know if the bearings are "going bad," and should we do it ourselves or take it to a professional?

TOM : You don't tell us what kind of car you have, Tegan. Some cars' wheel bearings are easy to change, and some are just a little less difficult than building a nuclear submarine in your backyard.

RAY : If you want to tackle it yourself, here's what you'd do: Assuming it's a front-wheel-drive vehicle, jack up the back end of the car. Then, with the engine off and the front wheels chocked, start by spinning the wheel that Sam suspects.

TOM : If a wheel bearing is gone, you almost always can either hear it or feel it. You might hear a slight growling sound. Or, if you hold on to the coil spring for the strut, you can actually feel the vibration of a bad bearing in your hand. It'll feel like there's grit or sand keeping the wheel from spinning smoothly.

RAY: You can compare one wheel against the other to see if one is noisier or grittier. If you conclude that one of the bearings is bad, then you can move on to stage two of Sam's diabolical plan to wreck your car -- doing the repair yourself.

TOM: Some cars are easy, and some aren't. Generally speaking, changing a rear wheel bearing on a front-wheel-drive car isn't too bad.

RAY : The problem is that you won't have some of the tools you'll need -- like a bearing press. But you can still do part of the job yourself. You can remove the disc or drum from the rear axle, and take that to a local machine shop and ask them to remove the bearing and replace it. And then put that brake assembly back on the car yourself.

TOM : What's the worst-case scenario? You misdiagnose it and replace a bearing that doesn't need replacing; you get stuck in the middle of the job and need to buy $300 worth of tools you'll never use again; and you do the job wrong and the wheel falls off.

RAY: And what's the best-case scenario? You do it all right and you save 100 bucks. So, given the cost-benefit analysis, I'd lean toward letting a professional handle this.

TOM : And I'd recommend taking Sam's car when you go out together from now on. Good luck, Tegan!