How do brake discs fail?

[erik]

I've heard of warped discs and seen one rear disc that had small radial cracks developing from the holes in the disc. I'm not sure how thin the cracked disc had worn and if the cracks were caused by it being thin, or some other reason (iirc, it didn't look that thin). From what I've read, warped discs seem to be due to faulty discs rather than the discs getting too thin.

So how do extremely worn discs fail? Anyone seen one? How thin were they and what was their thickness limit?

[FROSTY:Me]

Ive seen the result of a disk that flew to pieces. Its the ol thing with brakes-You expect em to work . when they dont you are in really deep doodoo . --we found a bit of disk further up the track that looked like a bit of pizza someone had taken a bit out of the pionty end

[reofix]

tolerances on brake discs are very conservative (as you would expect) from memory bmw new 4.5 mm .... throw away at 4mm

[JimO]

my Cagiva has brembos on it and they are being replaced under warranty as they are warped at 2500 miles (not ks)

[erik]

tolerances on brake discs are very conservative (as you would expect) from memory bmw new 4.5 mm .... throw away at 4mm

My bandit 400 and sv650s' discs are the same. The bandit's discs are worn to 3.5-3.6mm at the thinnest point now, so I'd better replace them. It's done 93,000km though, so it's not like I didn't get my money's worth out of them.

[dynamite]

I had a disk cracked from the vent holes out to the edge. took it into the bike shop to order a new one, it was still fairly unused they thought it was cos someone had heated it up to then cooled it quickly like going through water or something (makes sense remember chem classes at school heat a test tube up then put it under the tap) and also that, that one was a laminated disk, a couple bits of metal glued together so the disks were thin even though the over all width was still close to new. you will fail a wof with a cracked disk because as FROSTY said they are dangerous.