This is on a 69 L46 4spd vert. 100k miles. Planning to restore trailing arms and front rotors. Am presuming current rotors, which are riveted and presume to be original, are best to be replaced all around. I did some quick measurements with a caliper and pretty much every rotor I can get at least some readings below tolerance. I am in dialogue with several of the places (many of you know would know them) about doing this work. This thread is primarily not about recommendations on where to go but I would gladly accept them...here or in a PM.

So my core question is this. To my knowledge some places will rivet in replacement rotors and some olt them in. Should I care which way and why? I am well aware of how times have changed and gone are the days or turning rotors which are now a disposable item. I can't imagine any performance or durability difference between riveted or bolted. Also, not an NCRS judging consideration that I know of. Bolted would be bit easier to replace down the line...but that is an issue for the next owner as I will be long gone. My restoration philosophy is to strive for originality where it makes sense to me. Making sense can come from a lot of different angles. In and of itself originality would dictate rivet them in...but other than a purist interpretation does this really matter? Probably splitting hairs on this one ...but engineer types do that by nature.

 

Technically you don't need to bolt or rivet them. The replacements are shimmed to an acceptable run-out and as long as the shims are over a stud or two and the rotor is marked so it goes back on the proper orientation, the wheel nuts will hold everything together. They were riveted at the factory as they were machined as a matched set. You can tap and countersink the new rotors and they can be bolted together and that works just as good, some places do still machine them together "on the car" but not many I suspect.
I'd lay bets that there's way more running around that have the wheels just bolted on than there are that have the rotors riveted or bolted on... Including mine up till this winter when I changed for no real good reason other than I was installing new pads and decided why not.
M

 

What other cars rivet rotors to hubs?.......not sure, but I doubt many. This is old school stuff, backwards thinking and was done for whatever reason they did it back then. No longer necessary. I have put over 20,000 miles on my 77.....and they are not riveted, or bolted.....they are held on with the wheel lug nuts. I do have o-ring calipers....because again....they are better, and do withstand slight run out issues, moreso than lip seals. I would convert to o-ring calipers.....something that actually makes more sense and reliable for actual use. AND....honestly, I have zero pulsing in my rotors and ZERO shims. I believe my rotors dialed out perfectly without shims,......if I remember.....and they are completely held in place with the same wheel lug nuts that hold the wheel on.

Originality is fine, but it has its consequences. But then again.....I don't care about "original" at all.....I care about driving the car alot and having something reliable, more than trying to win any awards for originality. If you need rivet them on, then shim them and rivet them. Its going to take some tools and It only makes it harder when you need to change rotors. But......its your car. If using old ideas and old technology makes you enjoy it more, then I guess you have to deal with the consequences of it.

By the way....Bairs is big on riveting rotors, and when I had them work on my drivetrain after the first guy ripped me off......they riveted my rotors on....and refused to do it any other way, which I thought was BS given it is my car. I didn't appreciate them forcing it on me. Now if I need to work on my parking brake shoes, etc......I have to drill them out AGAIN. IMO......its absolute NONSENSE. I did have Gary tap and countersink my rears because he does that....and my cousin did the same on the fronts.

 

New rotors measure 1.250
Minimum measures 1.230
Discard at or less than 1.215

Suit yourself but you don't need rivets.

 

If you're going to take everything apart anyway, and you want to stay original, why not have the riveted hubs and rotors turned together like they did from the factory?
A little under spec will still work ok. Just do a clean up cut, they don't have to be 100% smooth, a few small grooves won't make much difference.

 

As the story goes, when our cars were rolling down the assembly line the rotors would not stay on without a caliper installed yet.
So, some guy with horn-rimmed glasses, clean white shirt with a pocket saver full of #2 pencils came up with the idea of rivets. (as a temporary clamp)

Oh those engineers. How many would you like to choke 40 yrs later?

 

I will work backward...as for choking engineers first on my list would be the guy who located the vacuum tank.

As for specs I measured..they varied a lot on a given rotor but some hit under 1.215. At 100k on the car gotta believe these are original rotors and they probably haven't been turned in tens of thousands of miles....given the way PO raped this car possibly never.

When I talk about my goal of originality it is simply how I choose to restore the car and not at all for any awards or points system just cuz someone sez. I am restoring this car out of the intrinsic love for the iconic piece of history that the 69 Corvette is and that's it. To preserve it for posterity. From a financial perspective I estimate I will have many thousands into it well beyond what it would sell for. Hopefully next caretaker is my son.

Thanks all. I got the input I needed to make my decisions.

 

Not quite clear

 

c3 caliper is hard mounted to the mount, unlike most cars now with slides, so theres no give if run out is excessive, the piston just moves in and out as the wheel turns, i drilled my rivets out and tapped the holes, used a tapered hex screw to mount the rotor to the hub,i then cut the front hub/rotor on a lathe, for the rears i shimmed the rotor with shim stock, i know my c3s aren't daily drivers, maybe over kill but when it comes to brakes ill put some effort in.

 

Interesting discussion on rotor runout and build type.

Before diving into the reasoning for how I build my TA and dial in the runout let’s look at how they were assembled new.

New 65-82 Corvette’s had the best brakes offered by GM. The parking brake setup could have been better but it will work for the most part if it is setup correctly.

The car was not designed to be on the road for 50 years. Back pre-1985 they were relatively cheap as a used car. Pre-1980 even more so. They were daily driven year round. The brakes developed issues with corrosion in the brake fluid that caused pitting in caliper bores and the fix was to replace them with new GM before SSBC in NY started ss sleeving them and saved them.

The rotors were perfect from the factory. There was no runout in them because the rotor was riveted to the front hub and rear axle flange and faced on the axle centerline. The braking surface was perpendicular to the center and had no runout.

So, what happened to create the monster so many owners have dealt with the past 40-50 years? Incorrect information and lack of proper training created this.

The first time the car was serviced and the rotors turned off the car started the corvette brake runout issue still occurring today. Not as bad today though because many owners know more than we did as kids working on these cars.

When the rotors are removed and turned on a lathe they are not turned relative to the axle center causing more, not less, runout. Add to this it is a huge mistake removing material from a small window to begin with. I think most, if not all rotors, are made in China now and many of them are not 1.250” new but rather 1.245” new possibly from metric conversion or just another example of lack of detail and quality control. Some of them have the ID of the hat too small so I have to bore them.

Bolting on a new or turned rotor without checking the runout correctly is a gross mistake and lack of understanding this simple system.
Using lip seal calipers and having runout over 005” typically means air pumping into the system and soft pedal or loss of pedal can result.

Bolting on a rotor that was removed the first time without proper prep to the rotor and flange will typically result in higher runout that was there before with the same rotor that wasn’t turned.

The old advice of indexing the rotor around the flange or hub is and has always been a hack way of addressing the issue and usually doesn’t work well. Think about it you just paid for rebuilt arms and you’re told to index your rotor? The rotor should always be part of a build but cost gets in the way and competition among those who rebuild them gets in the way.

So now we’re at the point of holding the rotor on. Cheap and fast is to let lug nuts hold them on. That will work as long as the runout is under 005”. I did a little test on this years ago by checking the runout with just the lug nuts holding them on. Once I got my dial- in, I loosened the lug nuts and retightened them and checked the runout only to find that it changed a few thousands. I did that several times and every time it changed. For those that think "close enough" is good enough then I can’t help you. For me it’s not good enough and it’s not about doing a fast cheap job- there’s plenty of other places that do that level of work but not me.

So that’s when I started checking bolting them on and locking in the runout where I want it which is under 003” total. I checked it the same way and didn’t find the runout changed. The method of riveting the rotor on and facing them works but if there is ever a need to remove the rotor then you’re back where this all started.

I read about this on many online forums and most have no clue why they were riveted on by GM and some of the answers I have seen are ridiculous and I wonder how they work on their own cars.

One last thing I cover in seminars on TA’s are some of the scams that have been used and continue to be used today. How many of you were told your axles were bent and had runout in them? I would ask that at my Carlisle seminars and would count the number of hands raised. Bent axles, indexing rotors, lug nuts as good as riveting rotors, yeah. I heard a bridge in Brooklyn is for sale or 6th Grand Sport is.

Good luck and good night Irene

 

not quite clear.

 

Just to be clear, I am the last person to question Gary on this subject. He has my full confidence and what he says goes to me.

My runouts on my 77 were under 0.003, and if I remember right were almost perfect. I remember being shocked and impressed how good they were. But I did NOT rivet or bolt the brake rotors to the front hubs, and have not rechecked them since I installed them. The wheels have been off and on many times, and never rechecked....so I suppose there is some runout changes. I will check that before I hit the road this spring. I have had no noticeable issues with the front brakes. The rears were rebuilt by Gary...so they have the countersunk screws and runout set by Gary. On the 69, all four have been drilled, tapped and countersunk, with Gary setting the rear runout. I will set the front runout.

So I believe hard fastening the rotor to the hubs, with proper shimming IS the way to do it. I just dislike the riveting.

Sorry Piste if I seemed harsh on the "originality: comments.....not really what you were asking about. I apologize. I don't need to lecture anyone on anything, let alone people trying to be faithful to a Corvette restoration. As you know.......its a difficult task.

 

Actually, the reason the rotors were riveted to the hubs was to facilitate machining the rotor faces to achieve trueness. That is why if you drill out the rivets, you want to be sure to reassemble the rotor in the exact same position to avoid introducing a runout problem.

 

seems like all this rotor stuff, rivet, bolt shim, runout, gets too deep, just get new rotors install them.
to answer the question rivets are not needed

 

Did you even read Post #11?

 

Here's a handy guide to the best practice, somehow hosted on a different Forum. Bolt, do no rivet.

https://www.digitalcorvettes.com/thr...dial-in.77063/

 

Hey, no worries, we good. Just wanted to clarify I am in this for I think many of same reasons as you...which is not about points or awards but rather love for the car. And I know you are rocking your custom thing...all good...I just am going a slightly different route. But I want to also be smart about things and in this case for me...that is bolting the rotors in. Rivets were original...but there is a better way to go here.

 

yes am thinking I am in for new rotors all around. but afaik runout could come from the hub or other places. In any event, always happy to be further educated but in this case I got the guy who gonna make it all right for my car.

 

Dear Gary,
Thank you for taking the time to explain all the steps it takes to properly check and correct rear rotor run-out.
You are a true professional! I've seen the photos of your work and it shows the care that you take on each job.

The new rotors being cut undersize is bad enough but the hat not correct either, glad you passed that information along.
Best regards, Pete.

 

Thank you Pete.
Yeah first started seeing rotor hat ID too small about 6 years ago. I saw it stock part store rotors and with some drilled and slotted ones shipped to me to use in a build.

Rotor runout issues, while I can face an axle flange I don't like to and many times it is not necessary, as the surface prep is causing the problem. After I held my seminars at Carlisle, I told guys to go check out the rebuilt arms on display. You will find all kinds of things walking Carlisle, from very good work to those selling them who have no clue of how to build them. I have seen bad parts used and no type of correct dial in on the arms on the tables of some the places. To be fair they were just resellers who bought a complete arm and resold it for a $100 but if you asked them how they were built you would get a blank stare of confusion. The worst part is the guy who thought he got a deal on something like that.