Question: Brake Rotors

[Vette79]

For Christmas/Birthday, I received new Brake Rotors and Hawk Brake Pads from VBP. This past summer, the calipers were replaced as well as the rubber brake lines, the Master Cylinder, and it was properly bled several times. The rear brake rotors no longer have the rivets but my fronts do. I drilled out the rivets on the front passenger side and then it occurred to me to do some more extensive research before moving forward. Is there any reason why I shouldn't replace the rotors since I now have new ones?

 

[Vettehead Mikey]

Rotors on C2/C3s rarely need replacement or 'turning' and are a very different animal than any other type of car. Unless your are damaged or worn beyond limits, leave them alone.

The act of separating the rotor from the hub or spindle disrupts the factory finishing machine step that eliminates runout. Blindly fitting a new rotor and not checking and correcting runout is asking for trouble.

Take a tour over on that other website (home of bubba) and you'll see plenty of proof.

 

[baxsom]

when your calipers were replaced was it a stock replacement or were they O ring seals. i asked the same question about runout to VB&P and they said that as long as I used hte O ring seal calipers then runout wasnt as much of an issue.

 

[Vette79]

I am coming to the conclusion that I should leave well enough alone. All four calipers have stainless sleeves with O-Ring seals and a proper bleeding has been done. I have a correct new Master Cylinder. I'm going to send the rotors back, keep the Hawk HPS Brake Pads and Adjustable Strut Rods. Thanks.......

 

[Vettehead Mikey]

You might want to keep them for a rainy day as the return shipping costs will probably make sending them back not worthwhile. If you are going to send them back, throw in the adjustable strut rods too. There's another goody that fixes something that's not broken. :bash

 

[Vette79]

You might want to keep them for a rainy day as the return shipping costs will probably make sending them back not worthwhile. If you are going to send them back, throw in the adjustable strut rods too. There's another goody that fixes something that's not broken. :bash

Mike, explain please. Are you saying to just go with Stock instead of adjustable?

 

[Vettehead Mikey]

Yes- the smart struts themselves don't do anything that that stock struts can't, they simply adjust 'differently'. They're usually sold with a centre bracket that lowers the inner attachment point of the strut. The goal of this is reduce the amount of camber change the rear wheels experience during hard cornering. Very nice theory but the difference this bracket makes is about 1/2 a degree IIRC. otfl

 

[GTR1999]

You know Mike, catalogs make the most useless things look great and worth the highprice charged. Look at those bearing grease tools sold everywhere!

 

[Vette79]

You might want to keep them for a rainy day as the return shipping costs will probably make sending them back not worthwhile. If you are going to send them back, throw in the adjustable strut rods too. There's another goody that fixes something that's not broken. :bash

Well, your right about shipping. Makes no sense now to ship them back. I'm better off just keeping what I have. I have a dial indicator now so I will eventually check and learn about runout when it gets warmer. I'll have enough to keep me busy in the spring with my Q-Jet and Struts. Thanks.

 

[kbunting]

Can you please tell me what the acceptable amount of runout is, or where I can find such specifications?
Thank you,
Kurt

 

[Vettehead Mikey]

.008" is the absolute limit, but.003" is far better and easy to achieve.

 

[kbunting]

Thank you Mikey

 

[GTR1999]

Mike
I sure wouldn't push past 005 with lip seal calipers, I think 008 is too much.
With that said I just setup original spindles and rotors,there were never turned. I did polish,not face, the flange in a lathe and removed high spots. I started out with 004" endplay but didn't like that, cut it down to 002 & 001" and bolted them in place with flat heads.
I've mentioned many times on most of these forums, that once the rotor and spindle/hubs are separated then the original relationship is lost. I have turned flanges to 0005" and still had runout with new rotors. I've had runout with new USA spindles and new rotors. Some setup under 005" but very few without some work.
I certainly agree with your past statements on NOT turning rotors, the spec is only 035" total and an inexperienced parts store or shop operator may wreck the rotor- I know this first hand! The one exception I would consider would be an on the car lathe but those aren't too common around here.

 

[Vette79]

So, I plan to finally check rotor runout this weekend. If it exceeds .005'' then replace the rotor? If rotor is whithin .005'' then just replace the brake pads and bed them in properly, right? I'm also curious as to adjusting the parking brake. I will follow the procedures that the shop manual points out but are there any tips or tricks that I need to know about? Thanks...

 

[Rex S]

You know Mike, catalogs make the most useless things look great and worth the highprice charged. Look at those bearing grease tools sold everywhere!

GTR, don't know how old you are but if you have never experianced all the good stuff in the old (50s, 60s, 70s) JC Whittney catalogs you just can't believe how true a statement you just made. If Ya have never seen one, it's worth the laughs to find and read one.

 

[GTR1999]

Ah yes, I used to read those in amazement as a kid. I figured a rebel plate, air horn, and girlie air freshners was all you need to keep your car on the road.

As for runout, the only reason to replace the rotors are if they are need or under the min. 1.215" thick. If yours are still riveted on then I suspect they'll be close. If not then there could be other reasons for high runout, rust,burrs, mostly unmachined mated parts. It can be corrected, I do it all the time.

 

[Peer81]

I have to agree with Gary's last reply.
First check the thickness of the rotor's. My fronts were below minimal spec and the rears were on the edge.
For runout I used silver paper in little pieces to get runout perfect. I got 3 rotors back to 0.002 runout and 1 rotor back to 0.001 runout.
As you will see, when you get near or below the 0.002. You'll see even pressing on the rotor will make the needle move. Good luck!

Btw. If you have the time, I think it would be nice to see how much the runout is on your still original rotors.

Greetings Peter