Guru_4_hire

Well I took off the tire finally and got my dads magnetic base and measured the rotor runout in the wheel in question.

I got .003 runout. So I think its time to replace the rotors.

It might be pusing .004 as well.

Jughead

Yeah, I thought .003 was the limit. :yesnod:

GTR1999

If .003 is the maximum you'll be ok. I think the book calls for .005 TRO. Be sure your indicator base isn't moving on you. If these are the fronts then you may be able to shim them closer. I use ss shim stock in between the hub and rotor. New rotors will not gaurantee no runout. I had .009" in a brand new USA rotor last year.
Gary

Guru_4_hire

well they are rusty as hell, and are getting pitted and have lines though them, and the edges look really rough. And I am getting air somewhere.

GTR1999

Well if they're otherwise shot then replace them. If just surface rust you can clean them up with 100 grit paper on a D/A or vibrating sander. Grooves will not clean up like this and the spec is only .035" between new and junk, 1.250-1.215" Do check the runout on the new rotors and be sure there is no rust,burrs,stampings, anything that will raise the surface and throw off your reading.
Gary

hunt4cleanair

I removed the piston springs and it neutralized runout. OK...with springs removed, it avoids the pulsating (tension of pistons against rotors) when rotors exhibit higher tolerances than recommended and when using silicone, avoids the air buildup that results in a mushy pedal.


[Modified by hunt4cleanair, 6:19 AM 4/18/2004]

Turbo-Jet

:skep: wha?

Turbo-Jet

front or rear rotor?
where did you position the gauge?

Guru_4_hire

Front rotor

I positioned the guage about in the middle of the rotor

lostpatrolman

arent those springs required to heat the water off of the rotors in the rain so you have brakes that work?

Turbo-Jet

the gauge should at the edge of the rotor as this is where the maximum runout will exist see here: http://forums.corvetteforum.com/zero...871#1547076871

.003" at the middle is maybe .005" at the max diameter, but this is still within spec. like others have said, if less than .005, and if the rotors are 1.215" or thicker, they are ok.

ps- the front bearings are preloaded so the measurement is pretty foolproof, but the rears are not. spindle endplay can give false runout readings, esp. if the half shafts are still coupled.

Turbo-Jet

ah, I see. removing the springs is a bandage fix, and risky if you have lip-seal style pistons.

hunt4cleanair

Quote:

ah, I see. removing the springs is a bandage fix, and risky if you have lip-seal style pistons.

And I've installed O rings and drove 2500 miles last year to Nashville and Hershey...without a glitch!

Does that make it work?

KJL

The spindles can be off as well. I just got 2 new spindles from Vansteel and I measured the run out on the surface of the flange and it measured .009!! I sent them an email but they never replied :mad I used foil tape and shimmed the rear of the rotors. I managed to get them to about .002. I guess my point is run out does not mean bad rotors. If they are obove the min thickness, just have them turned for 8 bucks at Napa.

Van Steel

KJL
Sorry but I never got your e-mail or else I would have replied back. How did you do your run out? :confused: What do consider the flange? Spindle flange or the the spindle itself just outside the lug studs. Did you have your bearing support set up and a bearing pressed on? Why didn't you call?

GTR1999

I've had new Tom's spindles runout over .005' on the flange. I had the spindle chucked in a lathe and rotated it by hand slowly without the studs installed. I even bought them in to a buddies machine rebuilding shop to have them checked on his lathe and still had runout in them. I corrected the problem because it wasn't worth the time and additional shipping cost to send them back.
Gary

KJL

I checked the spindle itself just outside the lugs. The outer bearings were pressed on and the inner I used a spare castle nut and carefully pressed the bearing into place. I then put on fresh castle nuts and finished the assembly off by torquing to 100 ft-lbs. Bearing endplay is .002". The only thing I can think of is I used the back side of the lug flange to help me push the seal into place with screw drivers. But I shutter to think that could have bent a spindle. Pressing the outer bearing on first means you have to also put the seal on the spindle and press in on after the spindle is located.

KJL

Yeah, I had runout problems with my stock spindles as well. I shimmed the rotors and they worked fine.

MotorHead

How do you go about shimming the rotors ?

KJL

I mark the high and low point on the rotors using the dial gauge. I mark the relative position on the rotor to the spindle. I pull the rotot off an add some foil tape(used for duct work) to the inside of the drum on face that is against spindle. I cover about 1/4 to 1/5th of the diameter. I bolt the rotor back on and check to see if I need to add another layer or remove some. Keep doing that until you dial it in. If you are checking the runout at the outside edge of the rotor, it doesn't take much to correct. Start with a single thickness layer. If you go to heavy, you'll just be chasing your tail around.
After that just check it from time to time when you need to remove a tire for something.