Wheel bearing checks specs

Actually they do. I've replaced bearings in machinery, where the only fault has been excessive play. Otherwise they've run perfectly smoothly. These are bearings that have not been subjected to any shock. On a wheel bearing, I would assume that once any significant play develops, road shock could crack the ball or race surfaces, leading to rapid failure.

With larger bearings that may be true, but IME bearings up to 75mm diameter at least are hardened right through. Maybe the balls, rollers, and track surfaces are slightly harder than the rest, but the difference, if any is only slight. Mike.

Nope but you can buy such systems for checking plant. Even the cheapest ones cost a four figure sum though & they all rely on the operator to a large extent.

I must admit it's ages since I had to change a wheel bearing, but the last one I did had definitely broken up on the track surfaces - indicating some form of case hardening. Think it was an Austin 1800 front wheel bearing.

If they rely on the operator, you might as well get him just to check the parts they're monitoring - if they are easily accessible like the parts the OP wants monitored on a car.

You can spot the problem earlier which gives you time to plan to fix it, factory downtimes rather more expensive than a hire car:-) & you expect to change bearings, I wouldn't be suprised if the majority of cars make it to the scrapyard with the original bearings in them.

Hi Guy

You can be one when you want, next time the babs come around with the Gattso summonses you just have to say "Do you have a warrant", then you're a warrant checker!

There's a specific name for that condition. I can't remember what it is. Dave Baker would probably know, but even through hardened metal can surface flake, if it is repeatedly hit. Particularly with extremely hard components, like those in a bearing. Presumably the impact locally stresses the surface. Enough to cause a thin layer to crack away from the main component, but not enough to crack the component completely. I'm just guessing. I don't really know why it happens, just that it does.. Once it does happen. In a bearing, the hardened flakes rapidly chew the bearing surfaces and ball cage until the bearing gives up completely. Mike.

Do wheels come off? Is there much noisy warning first?

Oh yes, they get noisy but they normally seize rather than fall off & once they start being noisy they can carry on for thousands of miles or (My last one) become unbearable in a couple of hundred miles.

I've never known wheels to come off. And yes. You get plenty of warning. It's usually quite progressive. Starts maybe just as a whine, which can last for quite a long time, gradually getting worse. The car stays drivable, but long before the bearing packs up completely, the noise and vibration will convince you that you'd better stop. :-) Mike.

It was somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Mike G" saying something like:

Take your pick. Before I looked at this, I was thinking 'spalling, but 'flaking' might be more it.

Definitely the condition I was referring to, but I thaught the name of it was a more unusual one. Thanks for the interesting website. I'll now be able to use more technical terms than just, 'It's buggered' :-) Mike.