Brake squeal

[850R]

Having fitted my Volvo 850 with the AP set up, callipers, rotors and matched with Carbotech pads, I’m getting lots of low speed brake squeal, drives me mad! I made sure I copper slipped the hell out of the of the pads, they were bedded in as per they should. The Callipers were refurbished, including new hardware etc

Has anyone had experience of this, should I spend a morning stripping them down again and seek some anti squeal shims etc?

Turning the radio up is simply not an option!!!

Thanks

[E-bmw]

Fit normal road pads.

[850R]

Thanks, not an option at the moment though.

[Drezza]

Happened when I did mine, went away after about 2k miles, just turn the radio up louder

[The Wookie]

TL:DR:

Anyone that says they've actually conclusively fixed brake squeal with copper slip is either lying or is the flukiest bd alive, particularly given that it's not even the right grease for the job as it breaks down at high temperature.

Your options are:
- Put up with it
- Try some different pad materials
- Set fire to it

From experience option 3 is the most effective and likely the most satisfying

Long version:

Hundreds if not thousands of brake applications have gone through here, I can only think of one single occasion where specifying Daikalub NVH grease on the abutment pins at regular intervals has actually solved an issue and it was a very specific high frequency squeal

For 99% of the cases, let me share some of the misery of what it means to be a brake engineer trying to solve an NVH issue on an application where you aren't able to do a proper CAE analysis:

Deliberately driving round in traffic for literally hours with instrumentation up to your eyeballs

Repeating the same obscure set of manoeuvres at walking pace on some god forsaken proving ground again and again for days/weeks on end.

Eventually you isolate the source of the noise to show that the brakes are only an excitation and that it's another part of the car actually causing the issue, then the customer says 'we can't change that' so you have to fix it even though it's not really your problem

Cue weeks putting cars on and off ramps, gluing accelerometers and bolting odd shaped mass dampers to random parts of the car

Doing it all again and again with dozens of pad iterations with different chamfer angles, cutouts, lubricated shims, damped backing plates

Then once more round the loop with tiny variations in disc/caliper/bracket design for another several weeks

Then, my personal favourite part, you get it to a point where you're happy enough with it, hand the car to someone else in your department to validate only to find their driving style is slightly different and it squeals like fk as they're driving it out of the car park

Going round the circle for literally months, gradually chipping away at the noise until you arrive at an acceptable production solution where you only get a grumpy e-mail every 6 months from the customer's quality engineer when there's a fringe tolerance car that still squeals, even though it's their fking bit of the car that's always been the problem and you could fit any similar brake system to it and it would have exactly the same issue

ETA - Thank fk we now have a proper NVH brake dyno to significantly reduce (albeit not necessarily eliminate) this misery. Best million quid we've ever spent.

Edited by The Wookie on Thursday 21st January 15:44

[Far Cough]

Carbotech pads is your issue...... They are great but the downside is you sound like a double decker bus !!

[850R]

Thanks for the feedback, both funny and informative, I’m going to pop some anti squeal shims in regardless, another chap dropped me a PM about the pads too, they are mighty impressive I must say, fast road use and a handful of track days, if the shims do not help, well I guess I’m going to have to live with it!!!

Cheers though!!

[Dave Brand]

The Wookie said:

TL:DR:

Anyone that says they've actually conclusively fixed brake squeal with copper slip is either lying or is the flukiest bd alive, particularly given that it's not even the right grease for the job as it breaks down at high temperature.

Your options are:
- Put up with it
- Try some different pad materials
- Set fire to it

As one of my former colleagues, with a lot of experience in friction material formulation, said a long time ago: "anyone who claims to understand brake squeal is either a fool or a liar."

[LimSlip]

Copper grease has worked for me several times in the past to "fix" brake squeal, the problem with it is that it's usually only a temporary fix.

[The Wookie]

LimSlip said:

Copper grease has worked for me several times in the past to "fix" brake squeal, the problem with it is that it's usually only a temporary fix.

Just as likely to have been the act of taking everything off and putting it back together that cured the squeal temporarily

[thebraketester]

Use ceratec. Miles better than copper slip