R36 Brake Woes

[MrWolf]

Hi guys,

I've been having a very persistent (and annoying) issue with what I assume are my brakes.

Long story short, once warmed up, I get a high pitch squealing sound emanating from the front of the car. The characteristics are,

- Only when going <~20km/h
- Can be whilst rolling or accelerating
- Disappears the moment the brakes are tapped, but will re-appear once the brakes are released.
- Hard braking a few times seems to temporarily remediate the situation, but the sound returns after not long

The pads and rotors were replaced a touch over a year ago and there is no apparent impact on braking performance. Car has been scanned and there are no codes coming up.

This video is pretty much exactly what's happening, inclusive of sound (may need to turn up volume).

It is usually extremely loud and as you can imagine, not a good look for an R36

Any thoughts?

[gldgti]

I get the exact same symptoms with my allroad but on the rear.

I figure its the type of pad / rotor combination, just luck of what is in there. It wouldnt surprise me if it went away if I swapped pads (but I havent)

[Umai Naa!!]

What brand pads and rotors?

[MrWolf]

I get the exact same symptoms with my allroad but on the rear.

I figure its the type of pad / rotor combination, just luck of what is in there. It wouldnt surprise me if it went away if I swapped pads (but I havent)

Hmm, my pads up front and at the back are different, so maybe. I wouldn't have thought the combination would make a difference if the sound occurs without braking?

What brand pads and rotors?

DBA T3 rotors and TRW pads on the front. Rear wheels are using DBA T2s and QFM HPX pads.

[Martin]

So after changing the rotors and pads things were ok?
This problem started some time later?

I would be checking the stone guards for clearance and the wheel bearings for play
Also check for tiny grooves in the rotors - get them skimmed
Also check that the caliper is able to slide freely
Finally, smear a thin layer of copper grease across the back of the brake pad

[Umai Naa!!]

I think the answer lies in the pad/rotor combo.

[MrWolf]

So after changing the rotors and pads things were ok?
This problem started some time later?

I would be checking the stone guards for clearance and the wheel bearings for play
Also check for tiny grooves in the rotors - get them skimmed
Also check that the caliper is able to slide freely
Finally, smear a thin layer of copper grease across the back of the brake pad

Thanks for the list Martin. I'll have a suss and see if any of the above makes a difference.

It kinda of just randomly started a little bit after changing the brakes. Hard to say exactly when.

I think the answer lies in the pad/rotor combo.

Are you able to elaborate more on why the combination would be the cause? Not saying you're wrong, but I'm just curious why it would make a difference in this instance.

[Martin]

Thanks for the list Martin. I'll have a suss and see if any of the above makes a difference.

No problem - it's just a logical check list - expect it to be non obvious but should be solvable

Are you able to elaborate more on why the combination would be the cause?

Umai Naa!! is very knowledgeable and experienced
There can be situations where specific rotor hardness and pad compound (fibre/ceramic/metal and friction level) don't work nicely together

[Umai Naa!!]

As per above, some pad and rotor combos are just plain noisy.

Moving away from OEM-style pads and rotors does tend to lead to this result though.

Current favourite for R36 owners is ATE Ceramic pads, with ATE discs. While you're probably looking at around $650 fitted, for the fronts alone, they are very good on performance, low noise and low dust. This is all probably too late for you now, but maybe something to kep in mind, if you're planning long-term ownership.

[Umai Naa!!]

Perhaps speak with your preferred workshop about getting the pads de-glazed, and having noise-reduction paste (Wurth makes a reputable one), applied to the pads and calipers?