Looking for some advice. I have a 92 with 40k on it. I got the car in November 04. I did not notice this until I was half way home and had hit a dip in the rood while changing interstates. When coming to a complete stop at about 1 or 2 miles an hour you can feel a surge from the breaks like there is a high spot on a rotor. I checked the run out on all for rotors and the left front was .012 it should be .006 or less. I replaced the front rotors and pads. I checked the run out again and it is still .012 on the left front. Do you think this could be the hub? I don’t know if this can be checked on the car. I don’t what to spend more money on the wrong thing. Any suggestions?
Thanks Louie

 

Do you stil feel pulsing in the pedal with the new pads & rotors?

 

Yes I still feel something grabing as the wheel moves.

 

I'm not clear, did you check the run-out with the rotor mounted on the car?

That is the best way to do it, if you didn't. If you did check it on the car, then disregard the the first section:

Note: you can buy the dial indicator holder at Autozone or Napa.

-Remove the wheel
-If possible place a plate or thick washers on the wheel bolts
-Reinstall just the lug-nuts and torque to spec
(the above simulates the wheel mounted)
-Remove the front brake pads.
-Attach a dial indicator to the brake caliper or any convienent stationary point.
-Set the dial indicator to zero and place the indicator pointer near the center of the brake rotor fire-path (the part that makes contact with the pad).
-Turn the rotor by hand and check the run out.



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Since you have a new rotor I wouldn't bother with measuring DTV (variations in disk thickness) or flatness.
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Major cause of rotor run-out is rust, corrosion and dirt between hub and rotor, and improper lug nut torque loading. That's why it is so important to inspect and clean mounting area between hub and rotor.

Make sure that the surface or the hub is clean and free of rust.

If that doesn't do the job. Your options are to have the rotor turned with an on car lathe.

Or they do make shims (correction plates) that fit between the hub and rotor. Or you can have the hub machined. Cheapest and quickest solution. http://www.brakealign.com/ is the most well known.
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It can also be the wheel bearing. Check the bearing and make sure it's seated properly.
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If the run-out persists then eventually the the pulsation and judder will return.

 

Thanks Mighty-Mouse. I did most of the things you a suggested. I did check the run out with the rotor on the car. I also tried indexing the rotor on the hub with no success. I also cleaned the hub and rotor. I think I will try the shims this weekend to see if that works. Thanks for your in-depth replay.

 

I used the Brake-Align shims, and they work great! not cheap though, but about the only way to get the runout really close. I got mine down below .002 on all wheels.

 

How much $ are the brake-align shims? (SS Brakes has a similar idea about 20 years ago, taper angle ground shims.)

I'vev had success in the past with brass shim stock. Dial indicator, find the high spot, cut out .004" or so shim stock and put it between the spindle and rotor faces 180 degrees opposite high spot, bolt together and re-check and trial and error as necessary. This got me about .002" T.I.R., as I recall.

shim stock try MSC or mcmaster-carr or local machine shop cutting tool supply.

-85% Jimmy

 

I ordered 3 shims today 03/02. I did not ask what they cost. I will let you know how they work this weekend if they get here.

 

I put one of the shims on yesterday. The run out was 12k. After the shim was on it was 2.5k. I don't know how much each shim cost but the bill for 3 and shipping was $48. Maybe one the sponsors could carry them.