jrg

i have an '01, 6k miles and i've been noticing that sometimes when i'm reversing down the driveway i get a squeak as i apply the brakes gently.

anyone experience this?

thanx,
james

Texas S Vier

Believe this is standard on the S4 due to brake set-up (mainly has to do with dust or film that collects on rotor while parked)

2faS4u2pass

normal, nothing to worry about

Genuine NCC170S4

I had this startign at about 1500 miles. At the 5k service the dealer fixed it. No prob since.

TTS_4_to_A6

Normal. 15,000 miles here and they have squealed in reverse for as long as I have had the car.

FWK-S4

Frist, brake squeal is the brake pad vibraitng in the caliper.

Brake pads wear with a taper because when the brakes are applied, the rotation of the disc causes the leading edge of the pad to be pulled into the rotor and the trialing edge to be pulled away slightly (servo effect). As the pads wear, this taper matches the surface of the disc and the pads lie flat against it when applied. This is why new pads aren't as efficient and fade more than pads that have been "worn in".

When you back up, the rotation of the disc is reversed, so it tends to pull the new leading edge in, and throw the new trailing edge out (except that these are the trailing and leading edges, respectively in forward rotation). The result is that the pad doesn't sit flat agianst the disc when you are backing up, and the gap between the dics and the pad allows the pad to vibrate.

The S4 is particularly susceptible to this as the front brakes use four short front pads, which have a greater servo effect.

If you drove your car backwards for a week, the brakes would probably start squealing when you drove forward.

2faS4u2pass

until you drive the car forward to reverse...makes sense (?)

esfor

excellent explanation. thanks.

jrg

thanx for the explanation!