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

> wrote
> 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?

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.


> Or perhaps the
> dramatic difference in brake performance my boyfriend swears that he
> notices are simply due to the brake pads wore down?

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

Thanks for your advice Pete! 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?

The message . com>
from contains these words:

> 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?

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.

>
> 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?

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.


> 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

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

"Guy King" wrote
> 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.

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

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

> wrote in message
oups.com...
> 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
>

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

"Ronny" wrote
> 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

Yeah, no beeping on the B5 though, just a small icon on the dashboard.

Pete

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