Brake Judder!!! What is it? Why does it happen?

mark b.

Supporter
I also chased a similar problem, the shoulders on the wheel studs were protruding beyond the hub surface and not letting the brake rotor hats mount flat to the hub. Something to check.
 
Right then -- never had any success with Wilwood rotors or their pads, (plenty "judder"
2011 historics 001.jpg
experiences) I do use their calipers, 6 and 4 pots with 2lb residual valves
My rotors are 300 diameter x 32 , pads are 20 thick DTC70 (Hawk)
Rotors and pads need to be bedded -this procedure is a must! --pre bedded rotors even better
In my application this brake system sees 10 to 50 laps of high noise on 3 kilometer tracks per session
Allow rotors to float -- ally hats and iron discs expand and contract at differing rates and if rigid will warp enough to give pad knock off
 

mark b.

Supporter
What Flatchat said on the floating rotors. Mine are Coleman, they have T locks that you can use to convert to floating rotors but you have to use their rotors or they might be able to machine yours. Mine are 1 3/8" x 12 front and 1 1/4" x 12 rear btw. Balanced and stress relieved are the bomb.
 

Terry Oxandale

Skinny Man
Supporter
Brake pad compound low temp rating means they melt and leave pick up on the rotor -- basically
I use performance friction rotors and Hawk DTC70 pads --works for me -- and probably better knowledge out there tho
I use these as street/track pads (DTC 60 and 70) and they work very well, and have never had the transfer issue with them. Initial bite when cold is great, and remains consistent with increased heat through a fastest lap.
 

Howard Jones

Supporter
Ya, I got that wrong on post #19. My master cylinders (not reservoirs) are indeed lower that the calipers. I will need residual valves and have ordered some steel adapters so I can fit Wilwood valves from Pegasus racing. I have always bedded in pads as the manufacture advises. I did the original BP10s and then the A's & Bs. BUT I am thinking that this is a material transfer problem and there is a mixed pad material imbedded in the face of the rotors.

I will fresh cut the rotors and then re bed the A's & Bs. Then we will see what we have with the new residual valves, re faced rotors and newly bedded in pads.

Doc. All 4 rotors have .003 or less run out and there are no cracks in them at all.
 
What the issue is as the pad builds up heat it lets out gas.The gas builds up and when it gets to a point it cant escape from under the pad so it will push the pad back of the disk the evacuate.
This is why it gets worse as it gets hotter, more heat more gas.
Slot your rotors, when on slot is leaving the pad surface another slot must be entering, basically you always have a slot under the pad.
The amount of slots in a disk is in relation to pad size,small pad more slots.

Jim
 
The pad is building up gas and pushes the pad back of the disk , that is the shudder.
Slot your rotors so as one slot is leaving the pad another must be entering.
This will give the gas a escape path.
As your pad temp is increasing the issue is worse, also when it cools and you are streeting the car the issue is not there , no brake temp.

Jim
 
What the issue is as the pad builds up heat it lets out gas.The gas builds up and when it gets to a point it cant escape from under the pad so it will push the pad back of the disk the evacuate.
This is why it gets worse as it gets hotter, more heat more gas.
Slot your rotors, when on slot is leaving the pad surface another slot must be entering, basically you always have a slot under the pad.
The amount of slots in a disk is in relation to pad size,small pad more slots.

Jim

Sorry if this is double post something odd happening at this end
 
you need to slot your rotors,gas is building up under the pad when they get hot. the gas build up is the effect that you are experiencing.
 
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