"Glazed" Discs

The Monty · 09-04-2007, 06:00 PM

Have just looked at my rotors and they appear to have taken on a "Glazed" type looked, almost as though they have been hit with a polishing wheel. Im guessing this is what people call Glazed disks, but my question is, does it affect your rotors, how do you get them looking unglazed, and what causes them.
If anyone needs to know, the car is an AU1 Fairmont, and I do a lot of mountain driving.

bodes-sh · 09-04-2007, 06:19 PM

that's why they invented slotted rotors...about the only things it affects are braking performance, and usually they will squeal like anything aswell, it's just a normal thing to happen to brake rotors...there are a couple of ways to get rid of it, get them machined, or rum some sand / emery paper over them to scuff them up a bit, you can do the same with pads, sometimes helps to stop them squealing

The Monty · 09-04-2007, 06:28 PM

Hmm, I have slotteds, so I guess this shouldnt be happening. Just my front left is really noisy, like high pitched squealing when I turn left.

EvilChief · 09-04-2007, 08:59 PM

glazing happens to any type of rotors, occures after heavy and long braking such as towing a trailer or mountain driving mainly. rotors need to be machine to remove glazing, at the same time the pads get a light sanding to remove any grooves and uneven wear. glazed rotors reduce braking performance and encourages queeling.

just imagine having friction between tyres and a dry road and friction of tyres on a wet road, same principle.
oh and good luck with the emry paper over the rotors u will be there for hours and if they are warped wont do a difference, we only emry the rotors straight after machining them to give it some texture and eliminate any possible sqeeling, but we only give it a quick and very light hit while its still rotating on the bench

The Monty · 10-04-2007, 03:27 AM

Thanks evilchief, they are a little warped, so they do need machining anyway. Can you still machine slotteds as you would normal rotors, or are they different?

au2sw · 10-04-2007, 06:06 AM

if they are warped, my advice would be to just replace them, once they are warped, theres little you can do to fix them, as there are legal limits on how much you can machine a rotor/drum. if your replacing the rotors, replace the pads at the same time, never use old pads on new rotors, you'll find your brakes are below par if you do. and i dont know much about slotted rotors, but i would assume you would be able to machine them too, but im not 100% sure.
col

EvilChief · 10-04-2007, 01:23 PM

Quote:

Originally Posted by au2sw

if they are warped, my advice would be to just replace them, once they are warped, theres little you can do to fix them, as there are legal limits on how much you can machine a rotor/drum. if your replacing the rotors, replace the pads at the same time, never use old pads on new rotors, you'll find your brakes are below par if you do. and i dont know much about slotted rotors, but i would assume you would be able to machine them too, but im not 100% sure.
col

ahhhhm ... no mate ... warped rotors can be machine straight again, no need to throw them away if they are still well within minimum size limits. and as for new brake pads, again u can reuse them if there is still plenty of meat on them, they just need to be rubbed back to remove grooves and uneven wear. as for slottered and cross drilled rotors, they can be machined just like normal rotors

Chooka67 · 10-04-2007, 02:38 PM

just replace them

The Monty · 10-04-2007, 04:10 PM

Ummm, 20k's old discs, no. Not going to change 800 dollars worth of brakes, because I may be able to machine them. It doesnt even make sense. Thanks for the nice first post. And welcome.

The Monty · 10-04-2007, 04:12 PM

Thats just like saying, gee, my tyres need rotating, stuff it, Ill just replace them. Pfffftt..

The Monty · 10-04-2007, 04:14 PM

Quote:

Originally Posted by au2sw

if they are warped, my advice would be to just replace them, once they are warped, theres little you can do to fix them, as there are legal limits on how much you can machine a rotor/drum. if your replacing the rotors, replace the pads at the same time, never use old pads on new rotors, you'll find your brakes are below par if you do. and i dont know much about slotted rotors, but i would assume you would be able to machine them too, but im not 100% sure.
col

Discs are only 20 ooo k's old, so should be able to be machined as the warpage isnt that bad, and discs are supposed to have enough meat on them to be machined from new. They are DBA slotteds. And the pads are get changed at the same time, as I have Ultimates in at the moment, and I hate them.

EvilChief · 10-04-2007, 06:13 PM

Quote:

Originally Posted by Chooka67

just replace them

thats some very bad advice mate, if u dont know what u r talking about, then dont say anything

:

replacing rotors is only neccessary when rotors are undersized or cracked or damaged
recommended when rotors are xthou km old and ceverly warped and coming close to minimum thickness

EvilChief · 10-04-2007, 06:15 PM

monty: rotors can be machines several times, most have minimum thickness staped on them, otherwise download the catalogue from dba.com.au and look up ur model, colum D will show u ur minimum thickness

if u r still unsure about machining ur rotors, see an local expert and get their opinion

i do this for a living

au2sw · 11-04-2007, 06:11 AM

ok, to start with there was no mention of how bad the warp was when i first posted, for all i know it may have been sevre enough that that machining would take them to their legal limit, it does happen, i have seen it. and i guess pads is a personal choice, but i would replace them if my discs were getting a new face as i wouldnt worry about the machining until my pads were a bit on the low side (with still enough meat obviously), obviously depending what the surface of the disc is like though.
in monty's case, fairly new glazed discs, with slight warp, machine and all is good. and you want to replace your pads, so there is no issue there. but if they were fairly new and it didnt matter what pads you were using, a bit of emery tape to roughen them up (remove the glaze on them also) and re-fit them.
never meant to upset you you evilchief
col

Tornado · 11-04-2007, 11:18 AM

Quote:

Originally Posted by au2sw

never meant to upset you you evilchief
col

I think he was talking to Chooka67

The Monty · 11-04-2007, 03:04 PM

Quote:

Originally Posted by au2sw

ok, to start with there was no mention of how bad the warp was when i first posted, for all i know it may have been sevre enough that that machining would take them to their legal limit, it does happen, i have seen it. and i guess pads is a personal choice, but i would replace them if my discs were getting a new face as i wouldnt worry about the machining until my pads were a bit on the low side (with still enough meat obviously), obviously depending what the surface of the disc is like though.
in monty's case, fairly new glazed discs, with slight warp, machine and all is good. and you want to replace your pads, so there is no issue there. but if they were fairly new and it didnt matter what pads you were using, a bit of emery tape to roughen them up (remove the glaze on them also) and re-fit them.
never meant to upset you you evilchief
col

Nah, its all good. Ill try and get them machined, if it doesnt work, Ill buy newbies. But, yeah, I know that I never said how warped they are, and we all know how warped the AU1's get, so I reckon it should be ok. The warpage is not bad bad, its pretty bad when I was at the drags, trying to slow down from 150 k's in 400m.
I think I first warped them just after getting them, I went up through Mt. Neebo and Mt. Glorious, and down to Somerset, and I got massive brake fade. I got to the bottom, and they were starting to go red, then when I got back to Brissy, I went to a car wah, and I guess the water on them cooled them REALLY quick, and kinda killed them. Havent got any worse since though.

EvilChief · 11-04-2007, 07:37 PM

Quote:

Originally Posted by Tornado

I think he was talking to Chooka67

correct

chooka67 threw a commecnt wildly into this thread without explanation, which was totally wrong advise. such people and such advise drive me up the palm tree, as we hear these stories every day at work when customers come in and come up with some amazing internet sagas.

au2sw: i understand where u r coming from and u gave an explanation why, hence i was happy to explain my side in my first reply to you, and yes i have seen some nicely warped rotors too, which are too close to machining, but we only machine between .2 and .4mm in a rough cut and .1mm in a fine cat which totals in a max of .5mm per side, totaling 1mm overall and that has solved some of the worst warpages u can find, coming from sprint cars

as for pads, sure if they have 5 or 6mm left id recommend to replace them while at it, we normally dont recommend till 3 to 4mm per pad on a regular street car a bit more on a performance orientated car (or we know the owner gives it stick), but if u still have 10+mm, again no need to replace, especially when u run some good pads