[Logicoeur]

Originally Posted by F30_Fahrer

If you say rotors don't warp then what would cause all pulsing in the brakes? When I put the new rotors on the problem went away till the following winter and then it came back.

I never had this kind of problem with the stock brakes that came with the car.

We have winter temperatures here going down to -35 to -40C. I park the car in a warm garage and then go out in the freezing cold

That kind of pulsating is generally from pad deposits. In high salt areas like yours and mine steel rotors will take a beating and start showing ridges quickly. Take your finger and run it along the rotor face and you will see where the high spots are.

[thejeremyman9]

Originally Posted by Logicoeur

That kind of pulsating is generally from pad deposits. In high salt areas like yours and mine steel rotors will take a beating and start showing ridges quickly. Take your finger and run it along the rotor face and you will see where the high spots are.

This is correct. Warped rotors is a misnomer. They do not warp unless there is a manufacturing defect or something. Pad deposits create high spots on the face of the rotor which causes the vibration and pulsing as the pad goes over those spots. It might be imperceptible to your finger, however, as is only takes a tiny amount. The typical cause is abruptly hitting the brakes frequently, or holding your foot on the brake firmly when the pads and rotors are hot (such as at a stoplight at the bottom of a hill). You can just get your rotors turned if you want to get rid of them - they basically take the minimum amount of material off to remove the high spots and create a new surface for the 'low' spots.

[brigade24]

dimpled, slotted and drilled rotors invite deposits because they cannot hold as much heat as blanks. Less material means more heat on less surface so the pads basically cook onto whatever surface is left of the rotor...

notice how the m-sport brakes you have now are so amazing...they are also using blank rotors. Food for thought man.

[BigRedG80]

Thanks for the insight everyone. It looks like deposit buildup was the culprit on the dimpled and slotted rotors. I'm not sure how you can avoid getting buildup on them around here. Now that I have M-sport brakes with blank rotors which work great I have no desire to put on those dimpled and slotted rotors.

[thejeremyman9]

Originally Posted by F30_Fahrer

Thanks for the insight everyone. It looks like deposit buildup was the culprit on the dimpled and slotted rotors. I'm not sure how you can avoid getting buildup on them around here. Now that I have M-sport brakes with blank rotors which work great I have no desire to put on those dimpled and slotted rotors.

I would suggest the following:

1. Proper bedding procedure for new pads and rotors

2. Avoid abruptly hitting brakes (like a panic stop) all the time - hard stopping is fine, just apply pressure somewhat gradually. My fiance has a really bad habit of abruptly hitting the brakes whenever she sees brake lights in front of her on the freeway, even if its only for a second, and it causes horrible deposits and vibration after only about a thousand miles on new pads and rotors, so this is a major cause if your driving habits arent "smooth" application of the brakes. Thankfully mazda 6 brakes are cheap, lol. You want the pad to contact the rotor then apply firm pressure and not "slam" the pad into the rotor if that makes sense.

3. Dont sit with your foot firmly on the brake when the brakes are hot (this is basically why at the end of a bedding procedure you drive for as long as possible without stopping to let them cool down)

Some people say going through bedding procedure with used brakes can help remove some of the high spots if they start to appear but YMMV.

[Logicoeur]

A good and hard brake session should clear up the deposits for a bit. But if the driving habits don't change the symptoms will return.

[nosam1g]

hey guys just upgraded to the m sport brake kit . i previously had the 4 piston in front and 1 in the rear.
this is the kit i bought
https://www.ecstuning.com/b-genuine-...4112221445kt3/

so my brakes already felt good .. but im up to 500hp now and wanted stronger braking power.. went with stoptech lines and motul 600 fluid..

first impressions the braking power is there because the rear have 2 pistons now .. but its not a significant increase in braking power. I think because i already had the 4 piston in the front . None the less i like the look and the red

the only problem i have is when windows down i can hear like a squeek or something when cruising

[CoopersF15]

Originally Posted by nosam1g

the only problem i have is when windows down i can hear like a squeek or something when cruising

This complaint has been made by many folks on here. IIRC there was nothing that could be done to fix the faint squeal/squeak you can hear at low speeds like when pulling out of a parking space or round a car park, or away from a stop light under gentle throttle.

I hate it too.

[johnung]

Originally Posted by nosam1g

hey guys just upgraded to the m sport brake kit . i previously had the 4 piston in front and 1 in the rear.
this is the kit i bought
https://www.ecstuning.com/b-genuine-...4112221445kt3/

so my brakes already felt good .. but im up to 500hp now and wanted stronger braking power.. went with stoptech lines and motul 600 fluid..

first impressions the braking power is there because the rear have 2 pistons now .. but its not a significant increase in braking power. I think because i already had the 4 piston in the front . None the less i like the look and the red

the only problem i have is when windows down i can hear like a squeek or something when cruising

So it sounds like you originally had the Grey Front Brembo 4-piston calipers over 340x30 plain rotors and the Rear 1-piston Bosch calipers over 330x20 plain rotors, probably with a stock or similar brake pad.

You replaced that setup with the M Performance Brake Kit with Front Brembo 4-piston calipers over 370x30 dimpled & slotted rotors and the Rear 2-piston Brembo calipers over 345x24 dimpled & slotted rotors, with a slightly different stock brake pad.

Here's what changed in your braking:

1) Eliminated Nosedive- the original rear 330 brakes paired with front Brembos, caused the car to nosedive under heavy braking. The rear Brembo 345 brakes are a better match so now under heavy braking your car squats very controllably. This is the improvement that you felt!

2) Decreased Fade- The braking power of the two Brembo front calipers (340 & 370) are essentially the same. They use identical pistons and identical pads. The only difference is that the casting of one is stretched by 15mm from the hub center.

(Yeah, I know that theoretically there is a difference, but practically when driving the two, there is not. Not going to feel a difference stopping at a red light. There are technical posts that can be read on this issue if anyone is curious)

But the larger 370mm rotor has more mass so it has the ability to absorb more heat before it starts to exhibit brake fade. Less fade is something that would be noticed in aggressive street driving with repeated hard braking, or in a tracking situation with the same.

3) Increased Noise- Dimpled & Slotted rotors are notoriously noisy. It's most noticeable when driving next to say a concrete median barrier where the noise is reflected back towards the car.

You also mentioned a squeaky noise. That's typically caused by a brake paste issue. BMW uses brake paste as an integral component in the brake system. Since yours is a new installation the paste may have been poorly applied in one or more of your corners. Sometimes paste is worn away and needs to be reapplied if the owner or a car wash blasts wheels with a pressure washer. Suspect that if squeaks begin or get worse.

Dimpled & Slotted rotors are a BMW marketing creation. They provide looks, but not much else, except profit to BMW. There's little actual brake performance improvement over plain rotors. And their noise is a detriment.

There's a reason why BMW supplies full crossdrilled rotors on the M3/M4. So do other manufacturers like Porsche, Mercedes, McLaren, etc on their street performance cars. Full crossdrilled rotors provide the best bite and they provide the best braking in the rain because water can't trap between pad and rotor surfaces.

I typically recommend StopTech full crossdrilled rotors for aftermarket braking improvement. They are high quality and they have directional internal vanes for optimal cooling. They are purchased in Left & Right part numbers for this reason. StopTech also makes a Front full floating full crossdrilled rotor in the stock 370x30 size that is amazing. See photo. It's the closest that I've seen to the full crossdrilled front rotors supplied in the BremboGT full racing kits costing many thousands of dollars more.

4) Brake pads are the least expensive brake component to change, that can make a big difference that the driver can really feel. BMW pads are no more than average in braking performance. It doesn't matter if BMW calls a set M Sport, or M Performance pads. They are nothing special. Hawk 5.0 are the best street performance pads. See photo. They have great bite and low light dust that washes right off, (compared to that sticky black BMW pad dust.)

5) Stock rubber brake hoses provide a mushy brake pedal feel because the hose momentarily balloons at initial force. Stainless steel brake lines have a firmer pedal feel for performance brakes. StopTech makes a set for about $110. See photo. Easy to change out next time brake fluid is replaced which should be done every two years for safety.

Below are my recommendations to improve what you have now. You can do them one at a time or separately.

1) There's nothing that can be done about the noise from the dimpled & slotted rotors other than to swap them out. But try to isolate any actual squeaks to figure out what corner or corners they are coming from. Have the brake paste checked and reapplied. See photo.

2) For about $200, you can swap out the BMW pads for Hawk 5.0 pads. I did this to my wife's car without telling her. She rarely notices changes that I make. But she came back from a trip raving that I must have done something because her brakes were suddenly better than they had ever been when her car was new.

3) Install stainless steel brake lines as described above. They will be an improvement. See photo for StopTech part numbers. Turner also seems to make a nice looking set.

Hope this helps!

[nosam1g]

Originally Posted by johnung

So it sounds like you originally had the Grey Front Brembo 4-piston calipers over 340x30 plain rotors and the Rear 1-piston Bosch calipers over 330x20 plain rotors, probably with a stock or similar brake pad.


Hope this helps!

Dam killer response !! i def might get those rotors .. they look sick ! .. i already have bmw pads that came with the kit and also those stop tech lines are in .. the lines didnt improve that much since my rubber ones were still good. My rotors dont sound squealing but like crickets just like you said on a side wall i can hear it