Pumba

Gentlemen,

About two years ago I became the first C5 Corvette owner to install the C6 ZR1 ceramic brakes on my 2002 Z06.

The brakes work fabulously! ! !

About one month ago I attempted to remove the front and rear calipers so I could inspect the brake pads. The front calipers came off without a hitch. Unfortunately, I could not remove the lower bolt that attaches the right rear caliper to the knuckle assembly.

So, today I took my Z06 over to D.J. Racing in Ortonville, Michigan. Dan Kellermeyer and I put the Z up on jack stands and with much effort we got the offending bolt assembly out of the caliper. What we found should be of concern to all Corvette owners who have these brakes.

First let me show you a picture of the rear caliper before I installed it on my Z:





Please note the two large attaching holes. In the bottom-view please note the line on both attaching ears. That line represents where a serrated steel insert is pressed into the aluminum caliper.


Next is a picture of the serrated insert:





Note how shallow and short the serrations are.


The next picture shows what we found when we were finally able to remove the lower bolt assembly:





The serrations have been completely stripped out of the inside of the bolt hole.


The next picture shows the upper attaching hole after we removed its serrated insert:





Notice how shallow the serrations are in the bolt boss and how they do not reach fully into the boss.


We repaired the stripped hole by applying J.B. Weld to the mating surfaces on the nut and to the interior of the attachment boss.

The front calipers do not use a serrated steel nut. They are threaded completely through the aluminum casting.

We decided to chase all the threads on the four calipers and we gently wire brushed the treads on all eight bolt assemblies. We found much blue thread sealant debris in each hole and on the bolts' threads.


We surmise that the blue thread sealant's strength was greater than the serrations ability to keep the nut from spinning.

In the future, we are going to apply a light coat of assembly lube to the bolt's threads and limit the assembly torque to 60 lb.-ft.

-

Falcon

J B Weld.....?????

Is that strong enough to hold the threaded piece and keep it from spinning when you torque it?

froggy47

Pumba

Falcon,

The short answer is yes.

I have seen J.B. Weld hold a pulley on a dry-sump pump for entire season after the normal fastener method failed.

0Anthony @ LGMotorsports

That begs the question, what about the thread locker they put on the bolts stock......is that to much?

Falcon

I've used JB Weld on a lot it things, but had never thought about using it in an application like that.

That's good to know it's that durable.

travisnd

What is the OEM torque spec? The C5 caliper bracket bolts are 125 ft/lbs. Will 60 be sufficient?

phipp85

I have a 2011 C6 and my service manual calls out 125 ft-lbs and no thread locker.

phipp85

I think so. First time I took my calipers off every bolt was super tight all the way to the last little bit of thread engagement. 1/2" breaker bar tight.

RX-Ben

use nord-locks and you can get away with a bit less torque so you don't destroy the parts.

Bill Dearborn

That could be an issue with any of the calipers that use that mounting method not just the Brembo rear calipers. Does anybody know how the Z06/GS rear calipers are assembled? Do they have serrated inserts like this or are they threaded like the Brembo fronts?

Or maybe somebody at the Bremo factory screwed up when making this caliper and messed up the holes in the caliper.

Bill

froggy47

Are you guys saying the high torque spec made those serrations grind away the alum?

My guess would be you just have a tough hard piece of steel that under heat, vibration, tiny amounts of movement simply acts like a file, filing away the alum.

Not a great design, it happens.

phipp85

That's the first thing I though of when I saw what happened. If the caliper holes that hold the inserts were cut too big the insert would spin on you rather easy.

Solofast

JB weld is an aluminum filled epoxy...

The operative word being epoxy. The problem is you can easily get these parts hot enough to where the epoxy will soften and be essentially worthless. The additional problem is that the aluminum will grow more than the steel and the epoxy, and it will pop loose, so the next time you go to remove it, if it has gotten hot enough, you will have the same problem taking it apart again.

If you doubt what I'm saying, hit it with a heat gun for just a few seconds and if it gets over 200 degrees F it will pop right out.

If it is all clamped tight, and there isn't much play in the hole, it will stay put, but it's likely going to be a pain taking it apart the next time if you don't fix it right.

I'd get a machine shop to make a slightly bigger version of the original and press it in, properly.

Maybe you can find something like this insert in inch dimensions as opposed to the metric stuff on the car and bore it out slightly to a bigger size and do that, or as I said, have a machinist make an insert that is similar.

Another approach would be to thread the hole in the caliper and make an insert that is threaded, inside and out. Someone with a lathe can do that pretty easily. Then you can use the high temp locktite on the thread surfaces as well as the faces, and that would hold it tighter than the interior thread since there is more area on the outer thread and flat surface so that would hold tighter than the inner smaller area thread. This would work well because when you are trying to take the bolt out, the drag on the thread would try to tighten the insert into the caliper, so it would come apart when you needed it to.

Figure out a way to fix it right or it's just going to continue to be a PITA every time you want to change pads.

Solofast

Another way to do it is get a keylock insert, they lock in place and never come out. You would have to make a spacer to replace the head on insert you are replacing, but if you made it out of aluminum you could put part of the insert into it and it won't come out.

McMaster Carr has them, and they also have some that have inch threads on the outside and metric on the inside. I've used them before and they work really well.