[mpop302]

My last coupe was plagued with brake dust and squeal.
Am I supposed to slam on the brakes hard a few times to bed the brakes on the new one?

[claykin]

Bedding your brakes is no guarantee to avoid squeal. I live in Florida and typically deal with squeal during the cooler winter months when humidity is lower. The squeal tends to stop as warmer more humid months arrive. That's been my experience over the years with several different BMW models, all with MSport brakes.

[Tenac]

Originally Posted by mpop302

My last coupe was plagued with brake dust and squeal.
Am I supposed to slam on the brakes hard a few times to bed the brakes on the new one?

I've always done this just for the want of my brakes to wear evenly. I found with all my BMW's its best to keep them clean as possible to avoid any noise. So far so good on that, however after rain/wash and parking with them wet they do make noise first few times of stopping. Bedding is designed to keep the surfaces matching and clean off any oil that might have been missed by the installer who cleans them upon replacement.

[cfm56d7b]

Squealing / squeaking brakes are usually caused by ...

1. Small rock or debris stuck between the pad and the rotor surface. What may be squealing sound could be in fact scraping sound instead.

2. Rust. Thin layer of rust will form if moisture deposits on the rotor surface. As rust gets shaved off by brake pads, high-pitched squeal will be typically generated.

3. Thinning pads which did not experience even wear on both sides. So the brake pad meets the rotor surface partially.

4. Brake pads with a high metallic content. As larger metal flakes are exposed in the brake compound, these flakes are literally dragged across the rotor surface causing noticeable squeaks.

How to reduce squeaking brakes:

- Ensure that the caliper pistons exert the same pressure across the entire brake pad surface
- Consider softer pads with an aggressive initial bite; and yes - these brake pads will generate dust which is an indicator that the pads are working as designed: preserve rotor life at the expense of the brake pads and expose a fresh brake pad surface with each revolution
- Consider rotors which help shave off brake compound to prevent glazing: slotted, J-hook rotors

[mpop302]

[QUOTE=cfm56d7b;30547436]Squealing / squeaking brakes are usually caused by ...

1. Small rock or debris stuck between the pad and the rotor surface. What may be squealing sound could be in fact scraping sound instead.

2. Rust. Thin layer of rust will form if moisture deposits on the rotor surface. As rust gets shaved off by brake pads, high-pitched squeal will be typically generated.

3. Thinning pads which did not experience even wear on both sides. So the brake pad meets the rotor surface partially.

4. Brake pads with a high metallic content. As larger metal flakes are exposed in the brake compound, these flakes are literally dragged across the rotor surface causing noticeable squeaks.

How to reduce squeaking brakes:

- Ensure that the caliper pistons exert the same pressure across the entire brake pad surface
- Consider softer pads with an aggressive initial bite; and yes - these brake pads will generate dust which is an indicator that the pads are working as designed: preserve rotor life at the expense of the brake pads and expose a fresh brake pad surface with each revolution
- Consider rotors which help shave off brake compound to prevent glazing: slotted, J-hook rotors

I think mine were due to dust. Power washing or going through car wash would eliminate sound for few hours until the wheel/rim gets dusty again (dustier wheels correlated to more squeak)

[cfm56d7b]

[QUOTE=mpop302;30547443]

Originally Posted by cfm56d7b

Squealing / squeaking brakes are usually caused by ...

1. Small rock or debris stuck between the pad and the rotor surface. What may be squealing sound could be in fact scraping sound instead.

2. Rust. Thin layer of rust will form if moisture deposits on the rotor surface. As rust gets shaved off by brake pads, high-pitched squeal will be typically generated.

3. Thinning pads which did not experience even wear on both sides. So the brake pad meets the rotor surface partially.

4. Brake pads with a high metallic content. As larger metal flakes are exposed in the brake compound, these flakes are literally dragged across the rotor surface causing noticeable squeaks.

How to reduce squeaking brakes:

- Ensure that the caliper pistons exert the same pressure across the entire brake pad surface
- Consider softer pads with an aggressive initial bite; and yes - these brake pads will generate dust which is an indicator that the pads are working as designed: preserve rotor life at the expense of the brake pads and expose a fresh brake pad surface with each revolution
- Consider rotors which help shave off brake compound to prevent glazing: slotted, J-hook rotors

I think mine were due to dust. Power washing or going through car wash would eliminate sound for few hours until the wheel/rim gets dusty again (dustier wheels correlated to more squeak)

Although "dusty" or softer brake pads were designed to reduce squealing, ironically "dusty" brake pads will generate squealing / squeaking sounds if the dust isn't removed quickly enough by the rotor rotation. Brake dust + heat can lead to a glazed brake pad or rotor surface. That's where having the right rotor helps. The rotor should shave a thin layer of brake pad compound with each revolution.

Glazing can happen even without significant dust being generated. Simply put: excessive heat will harden the brake friction material and cause glazing. Then, the hard glazing typically transfers from the pad surface onto the brake rotor.

Choosing the optimum brake pad can be an art form:

- Can operate effectively under heat
- Soft enough to allow being shaved by rotor rotation
- Hard enough not to produce too much dust