Street Rat

I didn't want to steal another's thread so I'm starting a new one.

I purchased some new rotors and calipers. I'm checking the runout on the right front. I haven't checked the left yet. I'm coming up with .011 out of true on the right rotor.

I checked the bearing adjustment prior to measuring and tightened it one more slot on the adjustment nut. It seems to have no slop in it now.


I have the .003 and .006 shims. When I add the .006 shims to the hub, It's still out .004 to .005. The Youtube videos that I have watched say not to stack the shims to obtain the correct runout.

Should I stack the shims or start over with a new hub?

By the way these are slotted and drilled rotors. It's a bitch to measure these things.

Thank In Advance,
Craig

Big2Bird

I see no reason why not to use two shims.
You want the rotor as close to zero as possible.
Greatly improves the braking, and also gets the wheels spinning true.

drwet

You need to get the runout down to .002" I would be a lot more comfortable with two full diameter shims than I would be with a bunch of pieces of shim stock, and there are a lot of guys doing that. If it were me, I'd use two shims.

GTR1999

Hi Craig
You can still dial in slotted rotors, there should be a small enough gap at the end of the slot and edge of the rotor. I set them up on the bench. I would first deburr the inside of the new rotor hat around the stud holes and inside hub edge. Then dress the hub holes, they are soft iron so the area around the holes raises up when the original rivets were installed. I use a 2" 90* grinder to clean them up. Once you have them dressed install the rotor and snug all 5 nuts evenly. I tap and use flat heads to install and dial in rotors but you can get by with just the lug nuts as many do.

Then install the indicator so it is solid and doesn't rock, put a preload on it and zero it. Slowly- very slowly rotate the rotor and find the low spot. Mark the rotor for reference and check again. If it stays where you marked it then add the shim to the stud closest to the low side, reset the lug nuts, and recheck it. With the front you can index the rotor on the hub to see if it improves before shimming. Also be careful if using a cheap import indicator, they will sometimes stick and that will drive you crazy.

If you take your time you should be able to dial them in to under 003". I have done this 100's of times and never had to turn a chip to dial in rotors, front or rear.

Street Rat

I watched the videos again.

I'm going to start from scratch this morning.

I will report my findings later today.

I'm shooting for .000 to .002 runout.

Mooser

I'll only add a couple of thoughts


If you are finding you need to shim a larger amount at one side, add some thinner shims to the middle studs so they are supported as well, otherwise it's bending that area when tightening the lugs and although probably not doing much out on the disc, can't be helping anything either. (The full taper disc shims are hard to find around here)

This is the numbers I came up with
Shim on a stud - Shim on the next 2 studs
.010 .0038
.006 .0023
.005 .0019
.003 .0011

Shim on/between 2 studs - Shim on the next 2 studs
.010 .0062
.006 .0037
.005 .0031
.003 .0019



Once you get it dialed in, mark the hub and the rotor with the right orientation and consider putting a dab of silicone adhesive on the shims so they stay in the right place




M

Street Rat

Update
I checked the runout on the hub. It has a .005 high spot. Is this so far out that I should be looking for a new hub?

Next thing was trying to get the runout adjusted to compensate. The combination of shims and rotating the rotor around in different locations finally yielded a runout of .002. Which is in the acceptable range. I would had rather have come up with .000. But after all of the trial and error of realigning shims and the rotor I'll leave it as is.

Your input?

drwet

Factory spec is .002" You should be fine. There should actually be a little runout to push the pads back away from the rotor, or at least that's what I'm told.

Big2Bird

That sounds like B.S.

Big2Bird

That last .002" will drive you batty. No worries.

GTR1999

Rotor bolted on, 002" runout - you're done. Pure and simple.

Street Rat

I'm already batty. I've been working on this one side for a day and a half.

Today we meet the challenge of the left side.

HeadsU.P.

H-m-m-m-m-m. How? Tension springs behind the pistons.

Street Rat

Just finished checking the left side. It only took about 30 minutes to get that side down to .002 runout. That's the good news.

The bad news. I tried to bolt on the new caliper (Wilwood D8-4). The darn rotor wouldn't turn. The pads are really tight against the rotor when I tighten the caliper mounting bolts. I think I'll start a new thread.