skiwi

got the car in the shop, after working with the dealer lead technican on an approach...

this saw the car up on the lift, the abs pump disabled, and 100km/hr achieved (virtually). after this, the squeal was easily identified. (esp will not allow the car power with the wheels off the ground, hence the disabling of the abs pump)

the squeal:
1) was front left brembo
2) remained upon pad replacement

the disc is true, the calliper straight, and no-one has any real idea what is the culprit. the discs at the front are being replaced overnight, and we will see if that has fixed the fault.

i know a bit about cars, but this sort of fault makes me think that the dealer tech earns his money.

on the plus side, with the car out of warranty in 6 months, i now have 2 new front discs, and new brake pads front & rear :-)
dave

skiwi

i've picked the car up after front disc replacement, and the squeal has gone.

why did the squeal disappear when the handbrake was put on (the event that meant we have been chasing our tails over the rear brakes for the last 2 months)? we think that it decreased the pressure in the hydraulic circuit enough to move the front left pad off the disc and stop the squeal.

PaulW

That was the question I was going to ask....hope it doesn't reappear...congrats!

Jkay

If the caliper is holding 1 pad on the rotor, why replace the rotor?

skiwi

the squeal only occurs at 100km/hr and over, and becomes much more pronounced when the brakes are *lightly* touched, and then will go away.

thinking it was an issue with the piston, we removed the backing plate and it made no difference. ditto replacing the pad.

although the disc appears true, i suspect that it isn't - and is warped enough to cause the problem at relatively high rotational speeds.

i'm 70% confident that we've got it, and if not, then a pad kit is due to go in.