Official: Brake Pad Knock Back Thread

[Silver69Camaro]

Originally Posted by Vegas69

Wilwood really should come out with a fix for this but I'm not holding my breath.

Why is it Wilwood's problem? Many people run Wilwood's with sticky tires and 9" axles without any problem at all...including myself (manual brakes or not). When I had a knockback issue, it was actually due to the front bearings.

Many floating caliper designs can suffer from this problem as well.

Did anybody try the 10lb residual with success? The 2lb valve is what most people use.

[Vegas69]

You're right, it's my problem. I just assumed spending 3k on brakes wouldn't have me chasing my tail for a year. First it started with a mis communication between Wilwood and Moser. Guess who got Wilwood to design an updated plate to fix the excessive bearing slide? I have two of them sitting on my bench for free directly from the manager at Wilwood. And they are twice as thick since one of the originals was tweaked from side force. Oh yeah, that's after I paid for a set of Currie plates and spent the money to have the bearing pressed on and off.

I'm experiencing it on the street as well. When I say street, I mean regular driving. I go around two corners and my pedal easily changes about an inch. On the autocross is goes almost to the floor. If it was a track only deal then I'd be thinking front hubs. I still think it's out back.

The 10lb residual will probably fix it but I like to take it on some long cruises. Maybe I should try some new bearing out back before I drop a fortune on a new hydraboost setup and master cylinder.

[Vegas69]

Just got off the phone with Moser. They have changed to a non rubber O ring type bearing from napa. Hmmmmmm........ No good reason was given.

[Bow Tie 67]

Originally Posted by Vegas69

Just got off the phone with Moser. They have changed to a non rubber O ring type bearing from napa. Hmmmmmm........ No good reason was given.

And this is a direct replacement for the set20 type bearing? Is it a roller or taper? Part number, pretty please?

[Bow Tie 67]

Todd heres an idea, can you adjust your rear brake bias to complete soft and drive the car to see if there is a difference. That maybe one way to confirm your problem is in the rear.

[Vegas69]

Actually thought about that. I just don't see C6 hubs having excessive deflection putting around town. I can feel no play in the front bearings. The napa number is 88128 but it's a roller.

[Silver69Camaro]

Originally Posted by Vegas69

I just don't see C6 hubs having excessive deflection putting around town.

They shouldn't, and if they did, you'd feel it with the car up in the air. Mine only do it on a very hard corner, but I can still manage it on the street.

One way to tell what the heck is going on is to find a parking lot large enough for you to do a "skidpad test". Run the car hard enough to push the pads back, then coast to a stop (still turning in a circle). Jack the car up and you'll see the pad that is pushed away from the rotor. It's a very small gap, but it will be obvious. Trouble is finding a location to do this.

[Vegas69]

Thanks Matt. I should verify it first. I'm pretty sure I used the parking brake since it's internal on Wilwood to come to a stop and jacked up both ends. I seem to remember the front pads having drag and the rears not.... That's what got me focused out back. I'm ordering the updated bearings out back. I have a suspicion of what may be going on here. Hell I can drive it around the block and wiggle the car around and the knockback will be there. I'd bet a large sum it's out back still....

I really hate to point the blame at Wilwood. They have also been good to me. The whole being the guinea pig for both companies and having all that axle end play just pissed me off. I'll figure it out....on my dime. LOL

[Stielow]

Originally Posted by Silver69Camaro

They shouldn't, and if they did, you'd feel it with the car up in the air. Mine only do it on a very hard corner, but I can still manage it on the street.

One way to tell what the heck is going on is to find a parking lot large enough for you to do a "skidpad test". Run the car hard enough to push the pads back, then coast to a stop (still turning in a circle). Jack the car up and you'll see the pad that is pushed away from the rotor. It's a very small gap, but it will be obvious. Trouble is finding a location to do this.

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

[Silver69Camaro]

Originally Posted by Vegas69

You're right, it's my problem. I just assumed spending 3k on brakes wouldn't have me chasing my tail for a year.

Nice. That's the attitude that makes me happy to help people out.