Glazed dics

[dazerc]

Hi
i done a couple of trackdays a few months ago but ever since my brakes havn't been as good.
I have replaced the brake fluid with some higher boiling point fluid that seamed to help but they still arn't as good. the discs don't look a bright silver colour but a more blueish tinge. i have done a good 3000 miles in the car since the trackday but the brakes don't seam to of got any better.
do i need new discs and pads???
Thanks

[rich 36]

You can get cream for that

[dilbert]

You can get the disks skimmed. There is a tool which fits the the stub axle and can skim the disks in situ. If the disks have got very hot, as is suggested by the colour, the hardness of the disks may have changed significantly. How it's changed depends on what thermal cycling the disks have been exposed to.

A budget alternative to skimming the disks, is to use a clean fine emery cloth wrapped around a block of wood with a flat face. If you are careful you can cut the glazed surface without damaging the disks. If you're going to change them anyhow, then you don't have to worry if you're not happy with the result.

[rich 36]

Hello matey, how are you?

[dazerc]

The discs have only been on the car about 5000 miles so have a bit of life left in them. so might give them a going over with the emery cloth. I think they have got really hot from the couple of trackdays where i done a 15 min session then let them cool for half hour or so then was back on track. The brkes never faded while on track which was good.

[dilbert]

rich 36 said:

Hello matey, how are you?

Yeah, I'm fine. Car is back now. No troubles at all getting it down, except with the windscreen washers. It failed the MOT on them, and the trouble was that the feedpipe from the washer bottle was blocked inside the tank.

Tried all manner of things, but in the end couldn't get the tank out because the securing strap bolts had gone rotten. Had I removed it, it would never have gone back on. In the end we improvised a waser bottle out of a jumbo screenwash can, and a piece of copper pipe.

MOT man was happy, and my new clutch held up fine, in fact the work has made the whole transmission a joy to use.

I only had one blast, other than the journey home, a total of about 500 miles, and it's now back off the road again. It's nice to have it home though, I can do lots of little jobs slow time. I'd forgotten how much I enjoy listening to the old girl really. I didn't us ethe stereo once during those 500 miles.

You?

[dilbert]

dazerc said:

The discs have only been on the car about 5000 miles so have a bit of life left in them. so might give them a going over with the emery cloth. I think they have got really hot from the couple of trackdays where i done a 15 min session then let them cool for half hour or so then was back on track. The brkes never faded while on track which was good.

Go gently with it. Technique really is key. Hold the block to the disk and turn the disc to get the motion. Don't use excessive pressure at the edges, and try *not* to work from the edges to the middle.

Skimming is way preferable if you can.

Edited by dilbert on Saturday 17th March 19:52

[dazerc]

Ok thanks

[rich 36]

Dilbert,

I've had a Mini washer bottle alongside the spare wheel,
for months now since mine went the same way
how odd.

Do I detect an element of retention in your voice

you'll be sorry losing that engine note in your ear my friend

richard

[dilbert]

rich 36 said:

Dilbert,

I've had a Mini washer bottle alongside the spare wheel,
for months now since mine went the same way
how odd.

Do I detect an element of retention in your voice

you'll be sorry losing that engine note in your ear my friend

richard

Hehe,

A bit of retention I suppose. I wouldn't want to have enjoyed it too much. If I had, and I have to sell it, I think my heart might break.

Hoping I can turn things around.

[rich 36]

Best of luck chap,
And I was indeed about to continue our frequent correspondence
as a matter of fact

[dilbert]

rich 36 said:

Best of luck chap,
And I was indeed about to continue our frequent correspondence
as a matter of fact

I'll keep you posted.

[GreenV8S]

dazerc said:

The discs have only been on the car about 5000 miles so have a bit of life left in them. so might give them a going over with the emery cloth. I think they have got really hot from the couple of trackdays where i done a 15 min session then let them cool for half hour or so then was back on track. The brkes never faded while on track which was good.

I doubt that's the problem, but if you're going to do that you must make sure you use Garnet paper not ordinary Al Oxide based stuff. It's worth checking that the discs are smooth and flat (no grooves, and both faces parallel). If the pads have got really hot they may have been cooked and need replacing. With ordinary single pot calipers you will sometimes find that the calipers flex so much under heavy braking that the pads take up a taper, which means you get uneven contact with the disc when it has all cooled down again. New pads will cure this, or just give it a few thousand miles of gentle driving.

[steve_d]

My thoughts are that the pads are cooked.
A new set may well fix any issue there may be with the disc.

Steve

[dern]

GreenV8S said:

but if you're going to do that you must make sure you use Garnet paper not ordinary Al Oxide based stuff.

Why is that? I've deglazed discs and pads before using aluminium oxide paper and it's been fine.

I normally stick a piece in an ordinary electric sander for the discs and lay a sheet on a level surface for the pads.

[GreenV8S]

dern said:

GreenV8S said:

but if you're going to do that you must make sure you use Garnet paper not ordinary Al Oxide based stuff.

Why is that? I've deglazed discs and pads before using aluminium oxide paper and it's been fine.

It's explained here: www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

[dern]

GreenV8S said:

dern said:

GreenV8S said:

but if you're going to do that you must make sure you use Garnet paper not ordinary Al Oxide based stuff.

Why is that? I've deglazed discs and pads before using aluminium oxide paper and it's been fine.

It's explained here: www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

Ah, won't do that again then. Thanks.