Pulsating Brakes!!

[dukeofpg]

I cannot figure what is going wrong with my front brakes. I have Brembo 4 piston brakes with Brembo stock 14" rotors. They pulse all the time. I actually have two sets of rotors. When I turn them, they show very little if any runout. I have tried three different style pads... stock Brembo, Hawk ceramic, and green stuff. When I change the brakes, I am super good to make sure every surface from the hub to the wheel are cleaned with a wire brush and that they are flat. Last Friday I installed the freshly turned rotors. They were dial indicated and showed almost zero run out. I put on seasoned pads from Hawk that had one or two track runs. They also had been properly seasoned when they were new. I flushed the brake fluid and put DOT 4 fluid in. The calipers were torqued to 75 ft lbs and lock tite was used on the threads. All rotors were cleaned with solvent and then soap and water.

The first drive was full of shutter at first. Within a few miles they began to smooth out. The car sat all weekend. This morning, as I drove to work, they were pulsating even with light stops. High speed or low speed same thing.

I do not want to go buy expensive rotors and pads until I resolve this issue.



The wheels are torqued to 105 ft lbs. The hubs seem tight. At least when I jack the car and wiggle the wheel, it does not move like a bad bearing.

The last time I did this same procedure, it took 3 days for the pulsating to show up.

What am I doing wrong??

/Users/dukeofpg/Desktop/IMG_0560.JPG

[#28]

I assume you're using spacers to clear the stock 18's. That could be it.

And the correct wheel torque is 125 ft/lbs.

[dukeofpg]

I assume you're using spacers to clear the stock 18's. That could be it.

And the correct wheel torque is 125 ft/lbs.

It could definitely be the lack of torque that is warping them. I also have a set of 19" TSW Donningtons that I use at the track. The problem persists even with them. The spacers are custom machined and are glued with construction adhesive to the rotors. I tried to weld them, but the rotor material is so hard that it would require too much heat for the cold steel spacers. At each point of assembly, I have checked for run out. Even with the wheels on, I see only .005" lateral wobble. Thanks for your response.

[WhatNext]

If the lateral runout of the rotors is only .005 then they are not the cause of the pulsing (although getting borderline). The 105 ft-lbs, if even on all the studs, will not cause pulsing. So I'm guessing some abnormal pad to rotor interaction. Maybe try some heavy high speed slow downs to get the pads and rotors friendly.

The soap and water is interesting. Never heard of this and definitely not needed. You didn't say what solvent you are using but a brake cleaner should be used.

The use of adhesive is another questionable item. Unless you loaded them with 1000s of lbs of load (like the load from the studs) to get metal to metal contact before the adhesive set, it will form a layer that will deform under load. Also I doubt the adhesive can take the heat from the brakes.

[dukeofpg]

I used a very thin film of adhesive and clamped the two parts together to be certain the surfaces were flat. Also the .005 run out was measured at the outer edge of the 18" wheel. That is so little deflection, I was surprised the wheel was that true. I'll try some aggressive stops. Hey what do I have to loose??

I really hope to upgrade to some different rotors and pads. I just want to resolve this first. Especially if I am ruining things because of my shade tree mechanics.

[WhatNext]

The .005 was on the edge of the rims, that's good. I would pull the wheels and check the rotors again. That would definitely eliminate them as the source. I know you said they were machined before but I've been surprised before with these newer brakes and if the rotors are still good, then we can rule them out and look elsewhere.

[dukeofpg]

I'll check the rotors Monday, Thanks

[dukeofpg]

Okay, I got in a little track time and rode the brakes hard for a 20 minute session on a road course. At first the pulsating brakes were terrible. Then in an instant the pulse went away. Maybe there was a contaminated spot on a rotor and it burned off at a 120 deceleration. So all is well currently.

[WhatNext]

OK that says a lot! It's not warped rotors but pad deposits.

Its the pads you are using. I've had that happen on a couple other vehicles after putting a certain brand pad on both (Raybestos advance tech pads). Some hard braking will transfer the pad material resulting in pulsing. Then they will clean off by dragging the brakes moderately.

I think you should consider changing to a different pad.

[Eidolon]

Whenever you switch pads, do you bed them to your rotors again?

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[dukeofpg]

OK that says a lot! It's not warped rotors but pad deposits.

Its the pads you are using. I've had that happen on a couple other vehicles after putting a certain brand pad on both (Raybestos advance tech pads). Some hard braking will transfer the pad material resulting in pulsing. Then they will clean off by dragging the brakes moderately.

I think you should consider changing to a different pad.


I have used three differing pads and I have two sets of rotors that have each been kiss cut twice. I had pulse with both pads bedded in with the newly turned rotors. Pad 1 Brembo stock Ceramic. Pad 2 Hawk Semi-Met. Pad 3 EBC Green stuff

[WhatNext]

OK this is a long shot. Since it happened with completely different pads it may be the pad interaction with newly cut rotor surfaces. A small amount of pad material ends up coating the rotors. This normal and part of how pads and rotors work. I know you said you bedded the new pads in. But since you have wiped off the big pulsing deposits, keep driving and see if it returns.

[dukeofpg]

OK this is a long shot. Since it happened with completely different pads it may be the pad interaction with newly cut rotor surfaces. A small amount of pad material ends up coating the rotors. This normal and part of how pads and rotors work. I know you said you bedded the new pads in. But since you have wiped off the big pulsing deposits, keep driving and see if it returns.

Okay, I have driven about 300 miles street and hwy and it is coming back, but ever so slightly. Of course I am overly sensitive and sniff out every shake rattle and roll. My son, 21 says that it is fine. My wife has never felt it