Shiming Front Rotors. Is this Ok?

[Mike E.]

The last time I had my front rotors turned on my '65 was about 34 years ago at the time I was told they were at the min thickness so I thought I should replace them while I’m restoring the chassis.

I wanted to retain the OE rivet look even though they can't be seen and found a set of rotors from Zip that had the rivet holes machined into them however after installing them I checked the run out and it was a disappointing .011” see the video below.

I could have the rotors turned with an on car brake lathe but really didn't want to remove that much material from the rotors. I checked and NAPA makes a shim plate that would correct run out to about .009” tried to order, but found the only ones available would correct .006” I actually ordered and thought I would try it to see how close I could get and it didn’t do much good.

I did some internet searching and found a thread where Gary Ramadei did the corrections by making shims from shim stock so I thought I would give it a try.

Gary didn’t post any pictures of his shims so I guess this is my question. The image below shows the shims on the hub prior to rotor installation. Does this look ok?







After dialing in the shims the best I could get was about .0015” of run out but I think that ‘s within spec.

So then to install the rivets. I used the same method Tracy Crisler used to install ball joint rivets. Heating the rivets with a torch till they were red hot on a bucking bar and forming the back side of the rivet with a 9X gun.














Mike

[Domenic T.]

Re: Shiming Front Rotors. Is this Ok?

Mike,
Looks like you went the extra mile, looks good in my book.

DOM

[Michael W.]

Re: Shiming Front Rotors. Is this Ok?

Very nice job indeed!

[Joe L.]

Re: Shiming Front Rotors. Is this Ok?

The last time I had my front rotors turned on my '65 was about 34 years ago at the time I was told they were at the min thickness so I thought I should replace them while I’m restoring the chassis.

I wanted to retain the OE rivet look even though they can't be seen and found a set of rotors from Zip that had the rivet holes machined into them however after installing them I checked the run out and it was a disappointing .011” see the video below.

I could have the rotors turned with an on car brake lathe but really didn't want to remove that much material from the rotors. I checked and NAPA makes a shim plate that would correct run out to about .009” tried to order, but found the only ones available would correct .006” I actually ordered and thought I would try it to see how close I could get and it didn’t do much good.

I did some internet searching and found a thread where Gary Ramadei did the corrections by making shims from shim stock so I thought I would give it a try.

Gary didn’t post any pictures of his shims so I guess this is my question. The image below shows the shims on the hub prior to rotor installation. Does this look ok?







After dialing in the shims the best I could get was about .0015” of run out but I think that ‘s within spec.

So then to install the rivets. I used the same method Tracy Crisler used to install ball joint rivets. Heating the rivets with a torch till they were red hot on a bucking bar and forming the rivet back side of the rivet with a 9X gun.














Mike

Mike-----


Most likely, the runout problem you first experienced was caused by the hub and not the new rotors. Originally, unfinished rotors were machined as an assembly with the hub so they never really tried to maintain a tight tolerance on either the rotors or hubs as separate pieces. You could probably have had the hub's rotor-mating surface trued to the hub centerline and when you subsequently installed the rotors you would have been within spec. However, what you did with the shims is fine. I've used that method previously (on the rears) with no problems, at all. If one has a really bad runout condition (e.g. .025" and I've seen it even worse than that), I think it's better to machine the hub or spindle rotor-mating surface and finish the correction as necessary with shims OR use the commercially available taper shims.

[Gene M.]

Re: Shiming Front Rotors. Is this Ok?

One needs to be aware of shimming can make the outer brake pad have too much preload against the rotor.

[Michael W.]

Re: Shiming Front Rotors. Is this Ok?

One needs to be aware of shimming can make the outer brake pad have too much preload against the rotor.

How do figure that Gene?

[Gary R.]

Re: Shiming Front Rotors. Is this Ok?

Mike
You did a real nice job, 0015 runout is very good. I shoot for under .002" so you shouldn't have a problem. I just use SS shim stock, I don't cut them as large in diameter as yours and usually only have to shim one or two studs.

I'd like to see your rivet install method if you have it on video. They look real good. I usually bolt them on for easy removal if needed, which would be in the rear arms anyway.

I've shimmed new and used rotors for years and never had a problem once dialed in.

[Edward B.]

Re: Shiming Front Rotors. Is this Ok?

Most likely, the runout problem you first experienced was caused by the hub and not the new rotors. Originally, unfinished rotors were machined as an assembly with the hub so they never really tried to maintain a tight tolerance on either the rotors or hubs as separate pieces. You could probably have had the hub's rotor-mating surface trued to the hub centerline and when you subsequently installed the rotors you would have been within spec. However, what you did with the shims is fine. I've used that method previously (on the rears) with no problems, at all. If one has a really bad runout condition (e.g. .025" and I've seen it even worse than that), I think it's better to machine the hub or spindle rotor-mating surface and finish the correction as necessary with shims OR use the commercially available taper shims.

+1 on truing the hubs.

[Mike E.]

Re: Shiming Front Rotors. Is this Ok?

Mike
You did a real nice job, 0015 runout is very good. I shoot for under .002" so you shouldn't have a problem. I just use SS shim stock, I don't cut them as large in diameter as yours and usually only have to shim one or two studs.

I'd like to see your rivet install method if you have it on video. They look real good. I usually bolt them on for easy removal if needed, which would be in the rear arms anyway.

I've shimmed new and used rotors for years and never had a problem once dialed in.

Unfortunately I didn’t take a video of the riveting. I followed basically the same technique that Tracy Crisler outlined in his procedure on installing ball joint rivets.

I used a long bar in this case the bar was flat and clamped to a workbench. I placed the rivet on a solid washer about the size penny. Heat the rivet till it was red hot, then grabbed the rotor hub assembly placed it over the hot rivet then used the rivet gun to form the rivet. You also should cover the wheel bearings because when you drive the rivet home small shards of steel flake off the rivet and you don't want to get those into the bearing.

One note I forgot to mention in the original post: The rivets alone DO NOT clamp the hub tight enough to the rotor to maintain the same run out. You must torque the lug bolts then check the final run out.

I'm not sure I'm up to doing the rears this way too because you would have to put everything together get the end play right then take it all apart to check run out which could be off a little by bearing the end play then rivet the rotor to rear spindle then put everything back together. Will see.

[Gary R.]

Re: Shiming Front Rotors. Is this Ok?

Thanks Mike.
Interesting on the clamping force, I would have to get them rock solid tight to maintain my setup. I will doing a set of 65's soon and may look at doing it or staying with the bolt on method since when I finish I know they are not going loosen or change the runout.
Again nice job!
Gary

[Joe L.]

Re: Shiming Front Rotors. Is this Ok?

Thanks Mike.
Interesting on the clamping force, I would have to get them rock solid tight to maintain my setup. I will doing a set of 65's soon and may look at doing it or staying with the bolt on method since when I finish I know they are not going loosen or change the runout.
Again nice job!
Gary

Gary and Mike------


I absolutely agree. If the rivets are installed in such a way that they don't clamp the rotor to the hub or spindle as-original, then the effort is purely "cosmetic". I'm not a big believer in doing mechanical things like this for "cosmetic" reasons. Plus, these rivets cannot be seen with the wheels installed on the car (as all cars are presented for judging). Besides, if one wants to have the rivet heads present in a non-functional manner (and without clamping as-original the rivets are essentially non-functional) just cut the rivet shanks short and epoxy the heads into the reliefs in the rotor hat. It's a lot easier and you'll end up with essentially as much functionality.

I also prefer using the internal head head screws as pictured below to fasten the rotor to the hub or spindle. All that's required is to slightly countersink the rivet holes in the rotor and tap the holes in the hub or spindle for 3/8-24 thread. The screws pictured are stainless but I usually use black phosphate-finished screws.

By the way, anyone that thinks using a non-original configuration even in unseen areas amounts to "heresy", don't use stainless steel sleeved calipers. They're not original, either. NO Corvette was ever originally delivered with such calipers. Don't over-bore or sleeve the engine, either. NO Corvette was ever delivered with an over-bored or sleeved engine. Don't install replacement valve guides or over-size stem valves. NO Corvette was ever originally delivered that way. Don't use tri-metal engine bearings. Few, if any, Corvettes were ever originally delivered that way. The list goes on......



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[Gary R.]

Re: Shiming Front Rotors. Is this Ok?

Hi Joe,
I agree and have been bolting on front and rear rotos for years. I can dial them in under 002 runout with turning a chip on them. I would consider the rivets as long as I can get them tight, which I probably can but I don't know if I can duplicate the factory appearance on them. For the ones I have done, riveting was not a concern.

[Gene M.]

Re: Shiming Front Rotors. Is this Ok?

How do figure that Gene?

excessive thickness of shims will make the rotor offset relative to the caliper towards the outside making the outer pad tighter to the rotor than the inner pad. Picture the rotor off center from the caliper. If your shimming is limited to .010" range no problem but the .025" to .030" range there could be problems centering rotor to caliper.

[Gary C.]

Re: Shiming Front Rotors. Is this Ok?

Mike,

Helps to use the car year icons. These icons can be sorted on as a search aid.

Gary
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