Time to change rotors?

[Formermercowner]

My front brakes make a whistle sound sometimes when i brake. I have new pads (driven 500km). The car is a bmw m4 2015 modell, never had a disc change and just now noticed small craks in the disc.

[hC1001]

The minimum thickness is etched on the rotor. I would go by that unless one of those cracks reach the edge of the rotor. The cracks developing in your rotors arent anything to worry about unless you are lower than min thickness.

[weytie]

Take of your wheel and punch out that baked brake dust in the holes. That's the reason why they start cracking, as the holes don't transfer any heat like that.

[SD ///M4]

Originally Posted by Formermercowner

My front brakes make a whistle sound sometimes when i brake. I have new pads (driven 500km). The car is a bmw m4 2015 modell, never had a disc change and just now noticed small craks in the disc.

How many miles on your car? What pads are you using? Do you track your car? If you do track your car, which pads do you use for the track?

That's a lot of pad dust in the holes. I've never seen that on my rotors. As mentioned above knocking out that dust would be the first step.

Putting a micrometer on the rotor is the best way to determine how thin the rotors are getting and if you get below the minimum thickness you should replace the rotors. From your picture you have quite a bit of ridge on the edge of the rotor.

I have a 2016 M4 that has 24 track days on it. All track days were done with Pagid RSL-29 pads and I've gone through two sets of those. My independent mechanic, who also tracks his car is recommending that I replace the rotors this year, but it's less of a need now since the car isn't driven due to stay-at-home orders and two upcoming track weekends have been cancelled.

His advice was to keep an eye on the rotors and if a crack extends and connects two holes or extends to the edge of the rotor, the rotor should be replaced immediately. Brakes are one of the most essential safety items on your car and it's always better to replace earlier rather than too late.

If you plan on replacing the rotors yourself I'd go ahead and order them now so that you have them on hand. Don't forget to order 4 rotor bolts with the rotors.

[Poiseuille]

sounds like whoever replaced your pads either didn't apply caliper grease (frequently called anti-squeal) to the backs of the pads and points of movement, or didn't do it right.
the 'squeal' you hear is actually VERY high frequency vibration from these parts, but no harm done, just remove the calipers and apply the grease. there's plenty on YouTube about this.

[Formermercowner]

Originally Posted by weytie

Take of your wheel and punch out that baked brake dust in the holes. That's the reason why they start cracking, as the holes don't transfer any heat like that.

Both the rotors on the front axle have all the holes filled with break dust which seems kind of odd, I'll start with making sure that they aren't stuffed. Thx for the reply!

[weytie]

Originally Posted by Formermercowner

Both the rotors on the front axle have all the holes filled with break dust which seems kind of odd, I'll start with making sure that they aren't stuffed. Thx for the reply!

And if you are in the possibility, do the back of the rotor aswell. At the back it will be the same i guess.

[Formermercowner]

Originally Posted by SD ///M4

How many miles on your car? What pads are you using? Do you track your car? If you do track your car, which pads do you use for the track?

That's a lot of pad dust in the holes. I've never seen that on my rotors. As mentioned above knocking out that dust would be the first step.

Putting a micrometer on the rotor is the best way to determine how thin the rotors are getting and if you get below the minimum thickness you should replace the rotors. From your picture you have quite a bit of ridge on the edge of the rotor.

I have a 2016 M4 that has 24 track days on it. All track days were done with Pagid RSL-29 pads and I've gone through two sets of those. My independent mechanic, who also tracks his car is recommending that I replace the rotors this year, but it's less of a need now since the car isn't driven due to stay-at-home orders and two upcoming track weekends have been cancelled.

His advice was to keep an eye on the rotors and if a crack extends and connects two holes or extends to the edge of the rotor, the rotor should be replaced immediately. Brakes are one of the most essential safety items on your car and it's always better to replace earlier rather than too late.

If you plan on replacing the rotors yourself I'd go ahead and order them now so that you have them on hand. Don't forget to order 4 rotor bolts with the rotors.

Originally Posted by SD ///M4

How many miles on your car? What pads are you using? Do you track your car? If you do track your car, which pads do you use for the track?

That's a lot of pad dust in the holes. I've never seen that on my rotors. As mentioned above knocking out that dust would be the first step.

Putting a micrometer on the rotor is the best way to determine how thin the rotors are getting and if you get below the minimum thickness you should replace the rotors. From your picture you have quite a bit of ridge on the edge of the rotor.

I have a 2016 M4 that has 24 track days on it. All track days were done with Pagid RSL-29 pads and I've gone through two sets of those. My independent mechanic, who also tracks his car is recommending that I replace the rotors this year, but it's less of a need now since the car isn't driven due to stay-at-home orders and two upcoming track weekends have been cancelled.

His advice was to keep an eye on the rotors and if a crack extends and connects two holes or extends to the edge of the rotor, the rotor should be replaced immediately. Brakes are one of the most essential safety items on your car and it's always better to replace earlier rather than to late.

If you plan on replacing the rotors yourself I'd go ahead and order them now so that you have them on hand. Don't forget to order 4 rotor bolts with the rotors.

The car has 4500 miles on it. I haven't tracked it yet but I've pushed the car pretty hard at som local twisty roads. I also find it weird that all if the holes are filled with break dust, but I will clean them.

You are right about the changing part, better safe than sorry. I've checked the rotors and the biggest crack is that in the picture, so there isn't any that are connected or extend to the edge of the rotors.

Sorry to hear that you must be isolated, I live in Sweden and we can move freely with our cars and I have a track session planned soon.

thank you for your reply!

[SD ///M4]

Originally Posted by Formermercowner

The car has 4500 miles on it.

You must mean 45,000 miles! A 2015 with 4500 miles would be rare, and definitely wouldn't have that kind of rotor wear.

[Formermercowner]

Originally Posted by SD ///M4

You must mean 45,000 miles! A 2015 with 4500 miles would be rare, and definitely wouldn't have that kind of rotor wear.

I converted it to US miles and its 27961miles. 45000km

[SD ///M4]

Originally Posted by Formermercowner

I converted it to US miles and its 27961miles. 45000km

You must be hard on your brakes. That's a lot of wear on the rotor for ~28,000 miles.

[irshaadd]

I've got a similar problem with my M4, I've noticed a squealing sound coming from the passenger side wheel occasionally when I brake. I've checked the brake pad and it looks fine, so not sure what the issue is.