Official: Brake Pad Knock Back Thread

[JohnC]

Originally Posted by Stielow

I have chased this problem for years...

List of what I have learned

• Roller bearing on a Ford 9 inch won't work for road racing.
  
  GM went to a stiffer front wheel bearing on the ZR1, STS-V and CTS-V to fix brake knock back.
  
  The bigger the rotors the bigger the problem.
  
  2 psi valves won't do it
  

The test I use is to do a figure eight in a parking lot at max lat then measure the brake pedel travel.

If you can't fix the problem learn how to left foot brake on the straights to pump up the brakes. I have done this for years.

Mark

Hi Mark,

Do you know the GM part number for the stiffer ZR1 front wheel bearing?
I want to make sure I have the right ones...

[Cris@JCG]

Let me see if I can help here..

1st I agree with Mark on the roller bearing, they are not the best for road racing.. tapper is the way to go..

2nd I would see about rotor run out on all 4 rotors, when setting up a car for racing I always have the rotors turned on a brake lathe.. when you have rotors that are assemble to hat, hub, & rotor you are going to have a stack up tolarance of pcs that have been machined probably flat & parallel within .002 to .004 & you added it up & you have an excessive amount of rotor run out which will knock back the pistons & have pulsation in your brake pedal.. run an indicator on the faces of your axles & hubs & see what your run out is..

3rd Caliper flexing on brackets.. The Wilwood parking brake assembly/caliper mount has some flex on it.. remove your pads & grab the caliper with your hands & you can move it.. For racing I make new brackets out of steel or aluminum with gussets machined into them to make them stiffer & it makes a difference on how the pedal feels & when you are going into corner.. look @ it this way.. large diameter rotors, hydraboost, high friction brake pads & racing .. got to have good stiff caliper mounts.. attached is a rear mounting caliper bracket I made for racing.. for asphalt racing steel brackets are welded on rear axle tubes & front brackets are welded on a fabricated spindle/upright also have floating rear ends with large bearings.. Take into consideration that in some forms of racing they want piston knock back to free up rotational weight.. can be done with o-rings in calipers instead of square cut rings

[Vegas69]

I'm starting with some tapered bearings. Moser should be sending them out today. Thanks for the info on the rear brackets being flimsy. I'll definitely look into that if I'm unhappy after my new tapered bearings.

[Bow Tie 67]

Originally Posted by Vegas69

I'm starting with some tapered bearings. Moser should be sending them out today. Thanks for the info on the rear brackets being flimsy. I'll definitely look into that if I'm unhappy after my new tapered bearings.

Todd the tapered bearing will not eliminate the knock-back, but they will survive large lateral loads, unlike a ball bearing.

Also for future reference the moser uses a common tapered bearing used on trucks the SET20 bearing. Napa, autozone, ect.. should carry these

[Vegas69]

It should eliminate some of it. I don't expect perfection but feel the roller bearing is causing at least 1/2 my problem. Moser said I won't have any end play with these new axles and bearings. I'll report back next week!

[ohcbird]

Todd-
any updates? I had heard that Wilwood now includes the improved bracket...

Gonzo-
Have those steel brackets proven to work or cure the issue, and do you sell them? How about thos pedals you made for the Wilwood base as well?

[Vegas69]

Kinda, I got the tapered bearing axles a few weeks ago but they were machined wrong. I took some measurments and sent them back to moser. They paid for shipping each way and the repair. I just got them back last Friday and proceeded to put them in but noticed one of the wheel studs got boogered up in there lathe and now I'm waiting on a stud. I'll be racing Sunday and that will be the true test. There is definitley no end play now in either side. I'll update you guys one I drive and race Sunday.

[Cris@JCG]

The new bracket from Wilwood helps but will not cure the problem.. If Vegas 69 gives me all the components that he has for the brake system I might be able to help.. If he was closer we would get this problem solved.. Maybe he will want to take a 5 hour drive!?!??

I have been thing of making these brackets for production..hmmmm

The machined pedals for the Wilwood base will see in the next couple of months in production.. tooling for the forgings will be ordered next week.. You didnt hear that from me though

Originally Posted by ohcbird

Todd-
any updates? I had heard that Wilwood now includes the improved bracket...

Gonzo-
Have those steel brackets proven to work or cure the issue, and do you sell them? How about thos pedals you made for the Wilwood base as well?

[Cris@JCG]

Here is an example of a caplier bracket I made for racing that I forgot to attach..