Lateral axle movement issues

[rsk68]

So this all started with the issues I was having with my Brakes as discussed in an earlier thread (no link)

Most notably in canyon driving I need to pump the brakes once to get good pedal feel, I originaly thought it was air in the line and have bled the brakes every way known to man, I now believe it is due to the rear axles pushing the pistons in a bit and forcing fluid back into the master cylinder, this weekend I will jack it up and measure the lateral movment with a dial indicator.

I was told by the Wilwood tech that no residual valve would cure this problem!

So some questions that you guys may be able to help me with, what would be the least movment you could get with a C clip? do i need to go to a C clip eliminator? could my C clips be worn thin? the Wilwood tech recomended a Torsen Diff due to very little lateral movement, anyone familiar with this diff?

Thanks

[parsonsj]

Yes, this condition is called pad knockback (or just knockback).

It can also be caused by worn front wheel bearings that allow the front rotor to push the pistons back in a bit. I fixed my knockback problem by replacing my front wheel bearings.

jp

[ponchopwr70]

I have the same plroblem. I think I posted this before, I have brand new rear bearings bolt in axels, brand new front bearings, bleed the brakes multiple times still have it. Its something I've learned to live with. I think it has to do with such a small bore size master and dia of disc that makes it more sensitive but thats just my theory.

[Payton King]

constant pressure and I also need to give a quick pump before I stopped. I thought it was air and bled the system and then put on a set of caliper pressure gauges front and rear. Come to find out I had a bad master cylinder and it was not holding pressure. Started off just like you said and progressively got worse.

I am running a twin master set-up and had about 2000 miles on the system. Front went bad and the rear is fine.

Longacre makes a set of caliper brake pressure gauges and they are surprisingly cheap.

It may be worth a shot

[Apogee]

Just my $.02, but we normally suggest no more than .010" axial runnout on a c-clip rear end with disc brakes. Most OE drum setups that I've measured had between .015"-.025" axial runnout for reference. It becomes more critical with fixed calipers versus floating calipers since the calipers can't float to align with the rotor. Some race shops will carry aftermarket c-clips in various thicknesses so that you can offset a sloppy c-clip groove or one that just wasn't machined to as tight of a tolerance as it should've been. I'm not sure if Todd at TCE still carries these, but he might be worth a call.

Tobin
KORE3

[CarlC]

Hey Rick,

You can try to shim out some of the axial displacement to determine if that is the problem. In the end, you may find that changing over to a Ford type housing end is best long-term solution.

[David Pozzi]

Rebuilding a worn positraction unit will help, also shims can be placed between the C clip and side gear to reduce play. I think there is a hardened valve spring shim that works in there, thicker C clips is great if you can find them.

I would think a residual pressure valve would help if the end play isn't too much.

[rsk68]

I finally got around to checking the side to side movement on the axle, it measured .035 on the pas side, i was frustrated with my travel indicator mounting so I didnt check the drivers side yet, ill check it tomorrow.
I think the best fix would be the ford housing ends and i still may go that way but will still check on shims, if i go Ford i will need all new axles made as mine are 3 inches shorter then stock.

[ProdigyCustoms]

You should not need to change to Ford neds. If you do you will need new axles, and brake backing kit (the mounting plate and brake drums) which are very expensive.
Do the trciks others here have talked about, you will be fine.

[rsk68]

frank,
your right and i will check on shimming it up before i go to crazy, theres a shop by my office that can help me with this and i will take the car there maybe tomorrow.

Thanks