Roger L

Hi Guys, today I changed the 4 rotors with NAPA premium quality and brake pads on "66 SB. Before changing rotors we removed the front hubs, checked bearings, new seals, cleaned and repacked hubs. They turn smoothly with no side play on spindle.
I don't have much history on car as I only own it for a few weeks. The old rotors appeared to be original, very poor condition. I have only driven the car about 100 miles so I don't have much history on how it feels driving it in terms of pulsation of brake pedal etc, The brakes were very spongy before brake job, also the car has power brakes. When I turn front rotors by hand I can see slight movement of brake pads with the rotors bolted down with lug nuts to hub, I don't have a dial indicator to measure it, but it is slightly noticeable. What is the allowable tolerance for run out on rotors. If the rotors are running out could the run-out be caused from bad hubs running out at the flange face, the flange faces were cleaned off with emery cloth and wire brushed to make certain mating surface for rotors was good without any contaminates trapped between the 2. In all probability these are the original hubs as removing the rotors required drilling out rivets and using a hydraulic press to push off hubs. If the rotors are running out, then caliper pistons would be constantly pulsating and therefore should I also replace the calipers after I find root cause for run out. What ever the cause is for run-out it was there before I bought car.
With the power brakes will the pulsation be noticeable in pedal as I haven't driven the car until I can get a direction on this.
I need some advice what to test, how and what would you change out, thanks for reading this Roger

PS- changed the parking brake and all cables to stainless steel as that was a nightmare to say the least

wombvette

The specification is about a thousandth, but I have found that .005 or less usually works. Most of the time run out will not cause pulsation in the pedal. They are probably OK unless you see a pronounced run out.

Ron Miller

I'd get a dial indicator and check them to see exactly what you have. I'd also try moving the rotor on the lug nuts one position at a time and rechecking runout in the next position to find where you have the minimum amount measured. Might be able to get by with just relocating the rotor in this manner.

Upon finding the minimum runout position, if it's still excessive, I think I'd try using some shim stock behind the rotor and wheel flange to correct the excessive runout to something permissible.

Just my thoughts . . . . . .

Scott Marzahl

I think the service manual allows .003" or you can pump air into system I was able to stay within .000-.003" using .005" brass shim stock and making washers.

magicv8

Pulsation is normally caused by rotors with hot spots from repeated high speed stops. The hot spots spread the pads when the rotor turns and the resulting pulse can be felt and often heard. IMO it is uncommon on Sting Ray disk brakes, but can occur on drum brakes. I also found it to be quite common on disk brakes of Thunderbirds I owned.

The hubs are fine as long as the bearing races are a snug fit. At the factory, the machining was finished with the hub and rotor already assembled, to prevent rotor runout. Once rotors are swapped, shims can be necessary.

mikem350

I bought brass shim stock at a hobby store..
VERY tedious process to add shims, torque lugs, and re-check....
got 'em down to like 2-3 thous

Roger L

Thanks guys, I bought dial caliper today, Right rotor is out .006 and left .009. I don't feel any pulsations in brake pedal. I will attempt to shim behind wheel studs and see if I can get it down to .002 but sound like a PITA. I also plan to replace the front calipers considering it's all coming apart again.

Westlotorn

Be sure to try all 5 rotation positions first, just pull the disc off and rotate one lug position and check run out again. You might get pretty close by rotating as mentioned in earlier post.

Ironcross

Re hub the hub to the rotors with the correct Dorman studs....then take it to a good auto parts store and have them cut with a fine cut to true the rotors up....that should correct it....