4th gen rear brake knock back....need solution

[AI#97]

So I have had it with the 10 bolt rear LS/LT brakes and pad knock back. We have been through the OEM front hubs, SKF/C5/Dulaney adapters and the 3rd gen bolt on spindle and know there is ZERO knockback in the front which leaves massive amounts from the rear due to the axle flange flex and the inner axle end wearing away.

What solutions have the 4th gen guys taken to minimize the rear pad knock back on their cars? My left shoe has no sole from all the maintenance tapping of the brake pedal after the WRL races this weekend. I'll probably put new axles in it as a start and keep the guide pins greased for the calipers but has anyone gone to a different rear brake package with success or found a specific brand of rear axle shaft that doesn't flex as much?

Muchos gracias.

[AllZWay]

It was really bad.. but for the record...I never had this issue with my car with all stock brakes and even stock rubber hoses on the rear. I have no idea what causes the issue, but certainly know how real it was.

[Pranav]

Mine was pretty bad at Hallett.

I pulled my c clips and found they we're worn and thin.

I put in fresh Dorman c clips and it was a night and day difference at NOLA, and I still have some end play that can be taken out if I make/find thicker than stock c clips.

Also if Glenn's car is running yukon axles, pull them and check for cracks.

As you recall I cracked and separated a new Yukon axle after iony four events. Got my money back and Ddtched them for used junkyard stock axles that Allford and I inspected for cracks.

Maybe the Yukon axles flex more than stock?

Start with the c clips. Measure them against a new pair of dormans from the store, you may be surprised.

[Pranav]

Also to confirm are you running stop techs up front with Max float hardware? None of that beveled washer bullshit

[Pranav]

Also once you get below halfway on rear pads, knock back increases. I am going to make some shims out of old pads for mine.

[AI#97]

Also to confirm are you running stop techs up front with Max float hardware? None of that beveled washer bullshit

Not stoptechs. Plan right now is to pull diff cover and check axles and c clips just like we used to and possibly move to Mustang rear calipers with screw in pistons.

[MikeP99Z]

Insert emoji of an evil laughing smiley face here.

[AI#97]

Insert emoji of an evil laughing smiley face here.

Where were you at WRL COTA wisenheimer?!

[MikeP99Z]

No, i wasn't available to attend due to work.

[Supercharged111]

Now this has me wondering if the rear is to blame on my car too. The last couple events have been horrible, I had to left foot tap after every corner of every race. Found a loose bearing up front so swapped it for junkyard fresh and it was less bad, but still no good.

[AI#97]

Now this has me wondering if the rear is to blame on my car too. The last couple events have been horrible, I had to left foot tap after every corner of every race. Found a loose bearing up front so swapped it for junkyard fresh and it was less bad, but still no good.


A few years ago with Misty's pink car, I went so far as to cap the rear brakes and drove the car around TWS for a couple laps without hitting the brakes (had free access during the week because she ran the place). I pulled into hot pit and went for the brakes and there was minimal knockback. This was with the old factory OEM hubs. We eventually went with the Dulaney adapters and SKF bearings and saw better results but still had to maintenance tap after every hard turn. Granted we were running 315 wide DOT R's. Eventually, I put an eaton HD in the car and that fixed some of the problem and then we put a 9" with tapered roller bearings. Problem was gone except it never had a very good pedal. The car we have now has a GREAT pedal. Far better than he old one she had even with a new MC. I can push/pull the axles in/out quite a bit. I've done all the typical stuff to make sure the calipers slide but after talking to Patterson, I had not though about the torsen causing some knockback with the way it is designed. That will be coming out and it will be getting an Eaton again. I still have the 9" housing but it requires you cut up the floor to get it in.

has anyone ever installed a rotating piston caliper from a Mustang? I realize there is some "custom" fabrication to do it but I have a milling machine and a ton of mustang junk laying around. Never had this problem on the mustang even when I had .135" and .180" of axle wear on the inner ends. Probably going to be my next attempt at curing this on this car over the off season.

[Pranav]

You're on the right track

But again like I said eliminating end play is key.

Can you try make thicker c clips to take your end play down to near zero?

My brakes are feeling pretty good right now with new c clips alone, but want to try take end play down to almost zero too.

[Pranav]

Also if your running a torsen consider buying a new center thurst block and measuring it against what you have.

Maybe that's worn too. I replaced mine last season after I had to cut out a stripped pin bolt.

[Supercharged111]

I just had an idea, why not weld a bead on top of a Dorman clip that's never seen oil, then flatten it back out with a sanding flapwheel on an angle grinder until it fits?

[Pranav]

I spoke with the guy that makes the thicker clips, and where the critical part is hardening

He's willing to make a set for us if I can get a few guys to commit

Need to talk to Al and see if I can get the blessing for this to be a test run for a 2020 RCR, but the single best thing I did to kill knock back is replacing worn c clips

If I can further redurlce end play by .01 on each side it will be mint.

All the bullshit around axle end flex and caliper springs pales compared to simply taking out end play with thicker or not worn c clips

[Supercharged111]

I just ordered some Dorman clips off of Amazon, nobody had any in town. We'll see what the car does on Feb 24th cheatin bastard practice day.

[Den34]

I had success by welding a small bead on the end of the axle and grinding or "tuning" it so size allowing a small amount for heat expansion. Ran those axles for years.
Bob

[Supercharged111]

I had success by welding a small bead on the end of the axle and grinding or "tuning" it so size allowing a small amount for heat expansion. Ran those axles for years.
Bob

Uncanny. Ryan just mentioned the same thing to me. I measured .029" play on the right side and .044 on the left, and .007" on the diff pin where the axles have been smooshing into it.

[Al Fernandez]

We'll have to measure the play on mine since it has c clip eliminators and I have plenty of knockback.

[Supercharged111]

Dorman clips came in today, they measured .159" thick. My old ones were .152" and .153", so definitely thicker. That plus a rosette weld on the axle end should have me good to go here. Going to leave a .010" gap per side, or as close as I can get. That'll eliminate.053" of end play. Along with new rear pads and tighter front hubs should be a more confidence inspiring car.

[Supercharged111]

I rosette welded the axles and got it down to ~.0115" on one side and ~.0135" on the other. I feel like the c clips got rid of more than just the 6 and 7 thou that I measured. We'll have to see how the car feels now at a cheatin' bastard practice session.

[liquidroam]

Maybe try this....???? https://www.pro-touring.com/threads/72134-Residual-valves-for-pad-knock-back?

[Supercharged111]

Maybe try this....???? https://www.pro-touring.com/threads/72134-Residual-valves-for-pad-knock-back?

I know on the older GMT400 and GMT800 trucks that the residual valve lived inside the master cylinder and that they used different valves for drum rear vs disc. I wonder if the Camaros have it inside the master or inside the now non-existent ABS pump?

[Al Fernandez]

I installed one in my car back in the day. Didn't make any difference.

[Supercharged111]

So for what it's worth, the tighter used stock hubs combined with new Dorman c clips and rosette welded axle shafts made a huge difference in braking performance. I still have knowingly spread C5 calipers and need a left foot poke after a sweeper, but braking is dramatically improved from last season and a great deal of confidence has been restored to the car. Got Pranav's axle clips today and can't wait to try them out! I measured them at .167" vs .159 on the Dormans.