Discs 'blueing'

**Libra** · Wednesday 30th June 2010, 10:48

When I picked my car up from the garage after having the MOT done, there was a little note sating that there was blueing on the discs. This would indicate that the discs have gotten hot. I have looked at them and there are two bands in the middle of the disc which are darker than the disc surface colour.

I had the discs, pads and brake fluid replaced last year with Volvo parts, so what can I do to stop the brakes getting so hot even when driving at normal speeds. I find that I have to really work the pedal for the brakes to start to work. Even my dad mention this. Its is almost as if the brakes are overwhelmed by the weight of the car.

What can I do?

**Liddo** · Wednesday 30th June 2010, 11:05

If the discs are getting that hot, doesnt that suggest that you may have sticky calipers???? If they are genuine discs and pads, I'd expect them to behave normally and wear correctly etc etc.

I suppose you'd need a rolling road and no braking to check properly. My old BM 5 series calipers would bind to the discs once they warmed up, so much so that the steering wheel would nearly jump out of my hands! New calipers sorted it though

**Libra** · Wednesday 30th June 2010, 11:30

Thanks for that. If what you suggest turns out to be right, surely new seals and 'bits' to refurbish the callipers would suffice considering that they are Brembo.

I have taken some pictures for you to see....
Fronts

the rear is normal - I think

**Liddo** · Wednesday 30th June 2010, 11:47

In no expert Darren, it was just a thought

I had something also similar to that aswell, and it turned out to be a faulty set of pads. The compound was ROCK hard, so i binned them, bought a new set, and the disc then wore evenly.

Its gonna take some messing i think

**Libra** · Wednesday 30th June 2010, 11:50

Thanks for your honest reply. I am no expert either, so I am asking around on forums.

**princepugh** · Wednesday 30th June 2010, 13:39

I'd get it looked at ASAP and concur, it is almost certainly caused by binding. If the pads/ disks get badly 'glazed' they'll have to be replaced - this would explain your braking symptoms too.

**Libra** · Wednesday 30th June 2010, 14:31

Originally Posted by princepugh

I'd get it looked at ASAP and concur, it is almost certainly caused by binding. If the pads/ disks get badly 'glazed' they'll have to be replaced - this would explain your braking symptoms too.

Thanks. I have emailed a brake specialist - Ian Goney of godspeedbrakes and see what he has to say.

**wegal** · Friday 2nd July 2010, 15:00

Looks to me like glazed pads. Change the pads for new ones and that should increase your brake feel. My pads very rarely wear out, i nearly always glaze them by about 50% wear. It doesnt have to be sticking caliper, although thats easy to check, just "rock " the car forwards on the clutch and see how she rolls, on a flat surface she should come to a gradual stop, if they are binding you will feel a braking effect.

Most likely you have just been a bit enthusiastic with the brakes and glazed the pads over, that wear line looks familiar to me :-) if the calipers where sticking it would probably only be one side and the blueing would be more even over the disk surface.

My money is on pads, its also the cheapest and fastest fix.

**pookie** · Friday 2nd July 2010, 23:22

Very old mechanic's trick.
To deglaze pads for diagnostic purposes etc. Remove pads, get some 180's grit production or whatever paper, put the production paper on a FLAT surface, rub the pads on the grit until the glazing has gone. Refit pads. Damn sight cheaper than new pads. Be careful of the dust.

Pookie

**wegal** · Saturday 3rd July 2010, 09:17

Yeah ive dont that too pookie lol, thing is that when you glaze the pad its not just the surface that is damaged the whole pad is heat treated and will be harder than it should be, the end result if you keep running them is loss of brake feel and faster wear on the disks, also if you do that make sure that the pads are put back in exactly the same position they came out of or you will have really odd brakes till they rebed.

For a short run, however its not a bad idea, its just a lot of work to strip them out and put em back, probably in the knowledge that you will have to do it again soon but with new pads, spend the money on new ones and do the job once.

**Libra** · Saturday 3rd July 2010, 09:53

cheers guys. When I went out Thursday, I gave the bakes a work out with two bigs is stops and the marks have gone from the discs. They are now the same colour all over.