Help me with my squealing front brakes

[benebob]

Put new pads on this summer on my 280i(axis ceramics with shims built in). They squealed horribly so I took 'em back off and lubed everything up with anti-squeal and beveled the leading edge of the pad. They were good for about 500 miles then the squeal returned. Any ideas on a way to come to a stop without drawing the glares?

[Jonny weggie]

Normally the squealing is caused by the brake pads being glazed over, the fact that you have put new one's on and greased all around suggest that they could still be touching the disc's so unless you try and tweek the pin's that hold them in,so that the pads are not touching the disc's, i would go out and try some hard braking somewhere safe to get them bedded in.
regards jonny...

[honestjohntoo]

Squeal comes mostly from the metallic parts of a brake installation, such as drum or disc, shoes and backplate, callipers, cylinders, pistons, etc. The energy input comes from the rubbing of the linings when the brakes are applied, but it will likely be the metallic parts which vibrate and emit noise.

For the vibration to exist there must be (air) spaces in the calliper/piston/pad or drum/shoe/cylinder bearing surfaces/assemblies that allows the excitation, such as dirt, wear, wrong parts, stuck pistons, etc.

Thus, common disc brake squeal cures are:

• Thoroughly clean all parts.

• Wash off the dust and debris. Brake cleaner or just plain water and washing-up liquid is fine.

• Pads must be identical in size and shape.

• Rogue/performance pads may be unsuitable or wrongly sized. Fit only manufacturers recommended items.

• Inspect for seized pistons and damaged dust seals.

• Upon reassembly use proprietary brake grease on all touching metal parts. Actually I use Copper-Ease.

• Fit any recommended metal shims.

• Ensure retaining pins/clips ([particularly clips) are not worn.

• Any or all of the above may contribute to a solution.

A useful work-around is to use a resilient material to form a shim on the pad backplate, this allowing some realignment to occur between the calliper and the pads. When no such material is used and brake grease is not effective, a pack of suitable self adhesive material can be purchased which is cut to shape and stuck to the clean backplate. After peeling off the protective paper, cover those areas of the backplate which contact either the piston or the calliper body. Offcuts can be used to build up a second layer where the piston makes contact. One can readily see how this might compensate for undue component wear or wrong parts.

Not recommended are:

• Roughing up friction surfaces creates less actual pad/disc contact and results only in reduced braking effect, as does:

• Chamfering the edges of the pad, which also reduces contact area and braking effect.

Sure, they may actually have an empirical effect on squeal but at the cost of reduced efficiency, not the best solution, methinks!

The bottom line is, regular and thorough routine maintenance.

[matt-man]

I had this problem and it turned out to be the pads.

I found that by doiung what you have done i would get a few miles of squeal free travelsbut within no time at all they were back to being noisy!

I had mintex road/track pads which were fantastic at stopping the car and no over heating, and have since swapped to standard AP lockhead pads. The squeal has vanished BUT they definatly arent as good..!!

[benebob]

Thanks guys, calibers are clean rust free (including pistons) and look like they just rolled out of the factory, not an ounce of dirt, shims are attached to the back of the pads on axis. No other issues aside from that 1-20 percent compression coming to a normal stop. All other stops are perfectly quite. I was hoping for a good technique to make it stop.

[honestjohntoo]

benebob said:

I was hoping for a good technique to make it stop.

You could try driving several hundred yards at the start of each journey, with the brake lightly applied to heat up the pads and discs and to speed up the bedding in process to achieve better contact between your new pads and the original discs.

As I said, the squealing is being generated by ill-fitting (ill-contacting) components making the metal components sing. If you get a marginal improvement, try increasing the distance heating/bedding-in until the noise is gone.

[SEvans]

matt-man said:

I had this problem and it turned out to be the pads.

I found that by doiung what you have done i would get a few miles of squeal free travelsbut within no time at all they were back to being noisy!

I had mintex road/track pads which were fantastic at stopping the car and no over heating, and have since swapped to standard AP lockhead pads. The squeal has vanished BUT they definatly arent as good..!!

Got exactly the same on mine. Mintex 1144 pads all round and squeal no matter what I have tried. Like the pads but may have to try something else once they wear out. Cheers Steve.

[adam quantrill]

I have 1144's and they don't squeak. Maybe you have a mouse nest in the caliper ;^)

Copaslip behind the pads/shims often works, or you could put in some extra shims cut from pop cans, it's worth a try, or just don't brake lightly but use the engine instead with the added bonus of some pops and crackles!

Edited by adam quantrill on Friday 23 October 17:22

[jeff m]

Run out guage on the disc

[Keri]

When I was trying to limit the squealing on a few of the WMS kits on the Wedge I found that grooved discs helped (second only to pad choice) - the grooves seem to reduce the buildup of resonance.

I can't help but think that the "bell" shape of the Granada disc makes things much worse!