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Thread: Burnt Disk Rotors???

  1. #1

    Default Burnt Disk Rotors???

    ok iv'e had a slight dilemma with the front left brake rotor. I had new disk and pads installed last friday and since then i have not driven the car hard at all and no hard breaking. Top speed iv'e travelled so far is 50kph.

    Anyways today i noticed that the front left rotor on the outer edge has a slight gold tinge to it where as the right hand side is all one colour. There is no difference in the feeling between the two distinct colours on the disk either.

    Im worried that ive stuffed up the rotors somehow. Should i be worried or is it nothing at all and im just stressing too much.

    heres a few pics.

    front left
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    front left again
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    front left again
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    front right
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    CURRENT: 2009 VW Passat R36


    PREVIOUS: 2008 Mazda 3 MPS

  2. #2
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    Default

    Probably over stressing, I am guessing that the caliper pistons weren't pushed in far enough when fitting the new pads and they were sticking. Thus the brakes overheated.

    I did the same on my rear on the merimbula cruise, disc looked exactly the same as yours. By the time I got back home it was back to normal colour.

    I did check that the wheel was free to spin at Merimbula.

  3. #3

    Default

    well its been that colour all day and the car hasnt been driven since 8:00am.... they do have the slight squeel still but not as often or as loud as when they were first installed

  4. #4

    Default

    Looks like a little glazing of the rotor to me. No big deal.

    When bedding in brakes i was always told just to get up to 60 ish kph then brake hard, then repeat for a while.

    Never heard about having to take it easy on the pads for a while or anything?

  5. #5
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    I've been told there is a specific bedding in process that is recommended.
    Quote Originally Posted by boost View Post
    When bedding in brakes i was always told just to get up to 60 ish kph then brake hard, then repeat for a while.
    From memory - repeating twelve times, starting moderate brake pressure each time braking a little harder up to max braking pressure.
    Alternatively, just drive normally but be aware for the first day or so that you have less brakes. A whole lot less brakes when you first drive away from the service.
    If things are glazed up too much, then some hard braking can clean it off...but ease off rather than hard stop. you want to avoid coming to a sudden stop under hard brakes while doing de-glazing because what can happen then is the glazing adheres to the pad and lifts off the disk leaving a pad shaped area on the disc with no glaze. Then the glaze has to wear away from the pad and there's some potential for excess wear because there's an uneven glazing surface on the disk.

    Someone correct me if any of that is terribly wrong, please.
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  6. #6

    Default

    wel tunehouse said they did the initial bed in procedure but i never asked them what they actually did and then they told me to just take it easy from then, which i have and this. kinda sucks and very embarrassing when u come to a stop and the brakes are squeeling like a dying cat lol

  7. #7
    Join Date
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    What combination of pads and rotors are you using ?, maybe shoot greg from gsl a quick message about your issue, he is very helpful with these sorts of dilemmas.

  8. #8

    Default

    matt they are the dba street series slotted and A1RM pads. bought from him as well

  9. #9

    Default

    hmmm ok well....i went past tunehouse saturday morning and when i got there the gold mark was gone from the rotors. On their initial inspection he told me they look fine and no glazing has occurred although the squealing is still there and alot of it. It is ok when the car is first driven in the mornings but once everything starts warming up its squeals no matter how hard or whenever i press the brakes and it is pissing me off but tony (guy from tunehouse) says its the pads because of the ceramic in them. I have booked it in for the coming friday and they are going to put like a anti squel paste thing on the back of the pads to see if that helps with it.

    Any other opinions and options as to why they might be squealing so much as i have always thought that brakes would quieten down once thy are warmed up properly???
    CURRENT: 2009 VW Passat R36


    PREVIOUS: 2008 Mazda 3 MPS

  10. #10
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    Squealing is caused partially by glazing, the noise is actually the pad vibrating on the disc. It is not helped by the air inside the piston expanding with heat and trying to escape (something like rhe reed in a mouthorgan) causes the squeal. Anti squeal paste helps sometimes by dampening the pad, but it usually only lasts a short time as it gets flattened. We used to put two hacksaw blades in a hacksaw and cut a slot at 45 degrees across the centre of the pad, successful in 80% of cases.

    Anti Squeal Shims were more successful than anything - a thin steel shim with about 1/3 of the circumference of the piston cut out of the shim. The Theory is that it allowed the air in the hollow piston to escape and therefore stopping the air expanding and trying to escape by pushing on the pad causing it not to sit flat and vibrate.

    My QFM pads squeal ever so slightly on first application and occassionally when brakes cool down, but it is so slight it's not worth doing anything to fix.

  11. #11

    Default

    Thanks for the info rd415. Might tell tunehouse to do that hacksaw thing. Well basically anything that can stopthe squealing as its getting to the point now like this morning its squealing as soon as i dive off and its soooooo loud and embarressing =(

  12. Default

    Sorry about the delay guys, we've been closed for the last week whilst we relocated to a larger warehouse.

    Quote Originally Posted by STEALTH_MPS View Post
    but tony (guy from tunehouse) says its the pads because of the ceramic in them.
    They're not a ceramic pad, they're an organo metallic. Squeal is caused by harmonics between the backing plate and the caliper itself, and generally isn't related to the actual pad material.

    If you've only done 700-800 k's, and only done very light driving, then the A1RM probably hasn't transferred enough material to the rotor yet. Most QFM pads, but in particular the A1RM are very sensitive to having a good layer of pad material laid down onto the rotor. The A1RM isn't a pad to be babied, you need to give it hell. I've ran it in both my past 2 rally cars, and also my Cross 6 tow vehicle, and they've been dead quiet all in 3 cars. I would start by taking them out, giving them a light rub on some smooth concrete, put them back in, go through a decent bed in procedure, and if you like, fit a soft anti-squeal shim kit. We stock EBC's one, and is about $17.50 per axle set.
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