Audi S4 2002 Warped Brake Rotors

Hi Everyone! I borrowed my boyfriend's Audi the other day and drove for four miles with the hand brakes on. Of course, the brakes started smelling like
burnt rubber and my boyfriend is pretty upset about this. My question is, how can you tell if the brake rotors are warped? Or perhaps the dramatic difference in brake performance my boyfriend swears that he notices are simply due to the brake pads wore down? Ultimately, I am very sorry for the damage, but I am skeptical of how much damage can driving for 4 miles w/ hand brakes on can do to a powerful car?
Thanks for all your help! Mei
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I'm assuming we're talking about rear rotors, as that's where the hand brake is applied. I doubt your action actually warped the rotors. More likely, you just wore down some of the pad material, and this you can inspect visually. If the pads are worn out, just get new ones.
I'm not sure how you could check if the rear rotors are warped. With the front ones it's easy - you just feel your steering wheel shaking when applying brakes. The rear brakes don't do a lot of braking and they're not anywhere near the steering elements, so you wouldn't be able to feel much if anything. If you suspect the rear rotors are warped, you can have them resurfaced, assuming they're still thick enough, but like I said, I seriously doubt you warped them in the first place.

Like I mentioned, the rear brakes don't do a whole lot of braking, so even if your pads are almost finished, you shouldn't feel "dramatic difference in brake performance". Maybe the brake fluid has boiled over and needs to be replaced? Again, I wouldn't think that driving with a handbrake on would normally cause this, but...
Pete
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Thanks for your advice Pete! :D I've also just called around to a few shops, and it's amazing the range of feedback I got from them. One was like "Oh no no, what have you done!" kinda advice and said that I must bring the car in immediately for inspection as this can cause dangerous driving. While another one was similar to your advice. You are right, it was only the back rotors that was heated up and gave off the burnt rubber smell. I looked over the front and back rotors and ran my finger on it (after it cooled off), and noticed that the back rotor's disks seem to depress about a milimeter or so as I run my finger from the outer ring in. But this depression was pretty consistent and smooth throughout the disk. Does this indicate warping? Or just normal wear & tear?
Also, I'll take up your advice on checking the brake fluid. Easy enough to do as a first check. I am thinking that my "action items" would be prioritized as following:
1) check brake fluid, add more if needed 2) check brake pads, change them if needed 3) bring car to shop for inspection, resurface back rotors if needed 4) change brake rotors as a last resort
What do you think?
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from snipped-for-privacy@gmail.com contains these words:

No, that's just wear. As the disc (as we Brits call 'em) spins and the pads press against it they wear down slowly.
Warping would be when it's not the same distance from a fixed point (like the hub) to the disc as you spin it. If you're bothered, jack it up and take a wheel off, blu-tac a pencil or something to the hub and adjust it to touch the disc. Spin the disc. If the pencil is sometimes touching, sometimes not - then it's warped. Or, more accurately, it has "run-out" - that's not run out as in expired, but run-out as in the plane of the disc is not at right angles to the axis of the hub.
--
Skipweasel
Si hoc legere scis nimium eruditionis habes.
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"Guy King" wrote

That's actually a much better explanation of warping. It's not that the thickness is different as I explained it, but that the surface is uneven because of deformation, usually due to heat.
Pete
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Thanks Guy, Thanks Pete! Your objective and knowlegeable advice is much appreciated. I'll see what I can do to help return my boyfriend's "other girlfriend" back to shape!
Thanks once again! Mei
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Symmetrical grooves in the rotor shouldn't be an issue. It happens sometimes when some harder element of the brake pad encounters the rotor and grinds it down over time. On the other hand, warping is normally associated with different thickness of a whole area of a rotor as compared to other areas. It usually happens when different parts of the rotor don't cool off evenly (like when you come to a complete stop afer a lot of hard braking and keep your foot on the brake pedal so the pads are still pressed hard against the rotor, but only in that one place). It would be difficult to verify this with your finger I suppose. You'd need to take the rotor off and actually measure it with a pretty exact equipment.

Sounds good, except (1). Adding more fluid may not necessarily take care of the issue. The fluid may be overworked and need replacing altogether. As it is, Audi recommends to replace it every 2 years, handbrake riding or not. :)
Pete
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I don't know how you could drive with the handbrake on, there is a massive warning light on the B6 as I have done it a few times, and it beeps like mad :)
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"Ronny" wrote

Yeah, no beeping on the B5 though, just a small icon on the dashboard.
Pete
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Mei, I am thinking that perhaps another action item might be -
5) Replace boyfriend.
Dan D '04 A4 1.8Tq MT-6 Central NJ USA
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Dano58 wrote:

Yes I think so too.
Possible reality: warped brake rotors, brake pads worn thin
Likely reality: warped boyfriend, girfriend's patience worn thin.
Solution: Replace failing parts with new.
/Robert
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