Brake Disk wear

( |-| |2 ][ $ · 4 Jul 2010 at 09:51

I got an advisory on my latest MOT for brake disk wear. I knew they were getting low as they've developed a lip on the each. Probably about 1mm in depth but it could easily been 0.5mm and I couldn't measure the difference.

How do I know when the disks need changing? Would be a shame to change them now if they've got another 1k miles left, on the opposite side I don't want to be going into a corner or coming off a slip road hard on the brakes and have a disk crack.

What does happen when they get too low?

MOOGLEYS · 4 Jul 2010 at 10:17

A small lip is nothing to worry about, Have a look at the condition of the discs and pads make sure there are no signs of deep scores or uneven wear. You average approx 2 sets of pads to a set of discs. This also depends on the car and how you use the brakes.

Eventually if the discs get to low then they could crack or shatter but you have to seriously neglect them for this to happen..

Fr0dders · 4 Jul 2010 at 11:28

garage are having you on.

My main dealer told me my discs needed doing as they were lipped, 6 months after telling me they still had plenty of metal left and were going strong.

Just because they are lipped doesnt mean all of a sudden they arent working.

They wont need replacing till the lip is so bid the pads dont make contact with the disc properly, and you will be able to feel it as the brakes wont brake properly.

Just keep an eye on it and dont let the lip get too big.

Lopéz · 4 Jul 2010 at 12:39

You can tell when a vented disc is really knackered, you can see the shape of the vanes throught the disc

Joshy · 4 Jul 2010 at 12:56

Probably best taking the wheels off, measuring the thickness of the discs with a vernier/micrometer and comparing it with the manufactures' minimum specifications.

Dogbreath · 4 Jul 2010 at 13:27

Joshy said:
Probably best taking the wheels off, measuring the thickness of the discs with a vernier/micrometer and comparing it with the manufactures' minimum specifications.

This is the only way of knowing for sure if the disks are in otherwise good condition.

However, if a set of disks only had 1000 miles left in them they would be extremely close to the minimum thickness already.

Deleted User 234324 · 4 Jul 2010 at 15:10

My old car had a 1-2mm lip on the discs, I took it to a local garage because of vibration when braking, discs were warped, they used a lathe to sheer off 1mm of disc to even it out.

Said there was still loads left, should last a year or more based on the mileage i did.