The accountant vs disc brakes

[Simon J]

Hi all,

First off, I'm really greatfull for all the good info you guys gave me over the last year or so.

The car is sitting on jack stands for over a year now and I finally got time to put it back on the road. What started with a simple axle seal swap turned into a full axles, axle seals and axle bearing swap (oh, and I'm redoing the trunk floor while having the car on stands, but that's an other topic). I also put in new longer studs and when I test fitted the whole assembly I noticed that the discs are touching (or very close to) the caliper bracket.

Here are pics from the driver side:
(from the top)141778
(from under)141779

Pics from the passenger side:
(from the top)141780
(from under)141781

I really don't know what can be the cause. Like I said I disassembled it over a year ago and I didn't take picture of the assembly before I tore it appart (should have known better that the weekend job would take a bit longer than expected...).

I'm pretty sure that there is something stupid that I'm forgetting, but I have no clue right now. Like I said, the discs and the caliper bracket are the same and the axles, seals, bearing and studs are brand new.

Any input is well appreciated :)

Thanks!

[Simon J]

I forgot to mention that it's the stock 10 bolt GM diff

[Simon J]

Ok, so now it seems like I installed too short axles.

The ones I installed are 29.62'' and apparently I should have 30.125''

Can this cause problems to the seal and bearing?

Thanks

[CliffsBlueCamaro]

Man, I hate when stuff like this happens.

But, I can definitely see how shorter axles would create the problem you're having with the discs. The disc rides on the axle, and the axle is now 1/2" more inboard, pulling the disc in with it.

Good luck, and let us know how things turn out!

[Simon J]

Thanks for the Ampathy Cliff

I really feel dumb to realize it after everything is installed :(
But, now the question is: Do I HAVE TO change the axles (in order to avoid seals/bearings problems) or can I just find new brackets and probably caliper to fit the new location of the discs?

I would hate to eat up bearings/seals because of my shorter axles.

[Skip Fix]

What rear discs? they look like 79-81 TA rear disc brackets.

Depends on how the axle is finished and where the bearing/seal is on it. The bearing/seal surface is generally polished smooth sometimes outboard the axle is rough. The 30 1/8 is the second gen length what rear housing is it? Second gens are wider than first gens. Most axle companies want the flange on the end to axle flange dimension.

[Simon J]

What rear discs? they look like 79-81 TA rear disc brackets.

Depends on how the axle is finished and where the bearing/seal is on it. The bearing/seal surface is generally polished smooth sometimes outboard the axle is rough. The 30 1/8 is the second gen length what rear housing is it? Second gens are wider than first gens. Most axle companies want the flange on the end to axle flange dimension.

Thanks Skip,

I do not have the "actual" info about the rear end, the guy I bought it from (9 years ago) told me it was from a 4th gen, but you're the 2nd person that suggests it's from an 81 camaro/TA.
Here how it fits:
141805

Right now I'm thinking about buying new axles with the correct lenght. It seems less expensive and less "trouble" than buying new calipers/brackets as well as spacers for my wheels.

Let me know if my thinking is wrong and if you could direct me to the correct parts that would be very helpfull.

Thanks again.

[Skip Fix]

If you measure mounting flange to mounting flange you can tell if it is a first gen or second gen. If it is in the first gen 68 Camaro I would think the leaf spring brackets would not line up unless new ones welded on in the correct spot.

What axles are in it?

[Simon J]

I'm away for the weekend, but the new axles I installed are summit's for a 68 camaro - 29.62"

And these are too short for the caliper to fit over the discs.

I will measure both axles (the old and new) to compare.

[andrewb70]

I don't have anything to add, other than letting you know that those are definitely not 4th Gen f-body brakes.

Andrew

[Skip Fix]

I've got a picture on home PC of a restored 81 TA rear to look at and see if that is what the system looks like. if they are float calipers sometimes the are just stock on the O ring and mounting bolts and can center themselves.

[Skip Fix]

Here are a few141900141901141902141903

[TheJDMan]

It is possible to install spacers between the axle flange and the brake rotor to move the rotor outboard. That is not what I would do but it is an option.

[Simon J]

Thanks skip, that is exactly what I have... well that is a MUCH CLEANER version of what I have. I just removed the newly installed axles and measured them against the old ones. The old ones are 30.12", the length of the 81 TA/Camaro, that's what I'm gonna order.


It is possible to install spacers between the axle flange and the brake rotor to move the rotor outboard. That is not what I would do but it is an option.

Steve, I was thinking about that option but quickly tossed it as I also use wheel spacers. That would be a lot of spacers.

I'll order new 30.12" axles tomorrow so I can put it all together again (I'm a lot quicker at putting it back together now!!) and move on with the new trunk floor and get that car back on the road (I didn't drive it in over a year and a half).
Next winter I'll probably clean the calipers and paint 'em and probably 'dip the wheels as well.

It may be a stupid question, but I'll ask anyways: Can I use the studs I just installed on the axles and put it in the newer axles? Or should I buy new studs anyways?

Thanks a lot for your input guys! You are great!

[Skip Fix]

So new axles-are you going to use hubcentric wheels or lugcentric? If you are going hubcentric like most factory wheels are the "regular" axles will not have a long enough brake pilot to engage the wheel as the rotor is thicker than the brake drum they are designed for. Moser will laugh at you and say use lugcentric wheels. You can weld on then machine an extension. Dutchman can make them that way. The factory rear disc axles had about a .700 length brake pilot to center the rotor and wheel.

I forgot what Dorman studs I used they have some slightly longer to work better with a rotor vs drum setup also.

So is this in your 68? I thought both the width and the spring mounts were wider on a second gen rear.
rear needed a freshening when I redid the 81's suspension. It was a little rusty and greasy. Sand blasted it and painted everything. Upgraded to 30 spline Eaton posi and Duthcman axles since the posi was way loose and one axle had pits in the bearing area.

[Simon J]

That is on my 68 Camaro. Here are 2 pics of the leaf on the diff, it looks "stock" to me but I'm no pro
141905

141906

I will have to say my wheels are hubcentric (they fit nicely on the "hub" section of the axle).

The axles I installed (the ones that are too short) were Summit's and the disc and wheel fit nice (as with the old axles).

Right now I'm looking for these PN from Summit:
https://www.summitracing.com/int/parts/yga-21242

https://www.summitracing.com/int/parts/aly-17122/overview/year/1981/make/chevrolet/model/camaro

https://www.summitracing.com/int/parts/spz-35050/overview/year/1981/make/chevrolet/model/camaro

I'm on a budget right now and do not want to invest too much, and my LT1 is probably delivering a bit under 300hp, so I'm not too worried about strenght right now.

Thanks again and happy 4th of July!

[CarlC]

Good call on new axles. Not sure off the top of my head but there may be insufficient spline engagement as well with the shorter axle.

[Simon J]

Good call on new axles. Not sure off the top of my head but there may be insufficient spline engagement as well with the shorter axle.

The way I see it, being "c clip" axles the splines should no be a problem. The problem is at the other end where the caliper/disc meet.

The question about the studs is still holding me back. Should I order new studs or can I reinstall the ones I already have?

Thanks

[Skip Fix]

That rear has been modified. You can see some extra bracing on the spring perches in the middle weld looks a little sloppier than factory so maybe they moved the perches for a first gen. It looks like the bracket for the flex line is welded to the rear-as you can see on my pictures the factory just used hard line to a block on the caliper. Does yours have an emergency brake ratchet on the caliper? The brackets will take a metric D154 caliper front caliper that has no e brake.
If you can press out the studs yes you can re use them a BF Hammer removal may tweak the threads or bend them slightly.

[Simon J]

I see what you mean about the bracing and spring perches being relocated. That's the fun about working on a car you did not build I guess hehe

I don't have e brake on the car right now...
About the studs, I'll just order new ones. My budget can do with a few $$

Thanks A LOT for your help, that's awesome!

[a67]

That rear is a corporate 10-bolt (8.5" ring gear). Can tell by the square lugs cast into the pumpkin at the bottom. The 1st gen 8.2" rear has a smooth bottom, no lugs, horns, or what not.

Bob.