Official: Brake Pad Knock Back Thread

[Vegas69]

I have to wonder how much pressure a brake booster and hydraboost puts on the system before any pressure is exerted on the pedal. There has to be a threshold amount. Maybe hydraboost will disclose it's specs in hope of a sale. They just might get it.

[Payton King]

and he stated the same to me....the 10 lbs residual valve fixed the problem.

I know some of the high end calipers have springs behind the pistons to stop the problem.

I have a therory that I have not proven as of yet. I think the lower volume of fluild used because of the smaller bore size in a manual system makes the problem more pronounced. Seems like you do not hear about it as much with a power set-up.

I am seriously considering converting to a DSE power system soon. I will let you know if my therory works out.

I did the same with the Currie plates and still have a little knock back, but not as bad as it was.

[Vegas69]

I may have to give the 10 lb residual valve a try out back. What's the worst that can happen? Strand me out in the desert with no water? I still think the factory has a solution for this in there rear disc setups on straight axles. All it can be is some residual pressure. Whether that's caused by power brakes or a factory residual valve I have no idea.

[Bow Tie 67]

Originally Posted by Vegas69

I may have to give the 10 lb residual valve a try out back. What's the worst that can happen? Strand me out in the desert with no water? I still think the factory has a solution for this in there rear disc setups on straight axles. All it can be is some residual pressure. Whether that's caused by power brakes or a factory residual valve I have no idea.

What factory cars run fixed calipers? I thought most use floating.

I have tapered bearings ( SET20 ) in my Moser, end-play is .015

I'm using Baer floaters with a C5 power booster, so I cant get any input other than the above end-play.

[Vegas69]

Thanks for the info. You are absolutely right, most factory setups are floating.

[Vegas69]

Ran a fast autocross this weekend and the brakes were useless. Unfortunately I'm going to have to go with a hydraboost unit since power brakes are not an option. My axles and bearing packs can't get any tighter. It's got to be fluid volume........ Wilwood really should come out with a fix for this but I'm not holding my breath.

[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?