Shimmy Shimmy - AGAIN!!!!

Getting a bad shimmy when applying the brakes after driving a few miles. This is 94 limited 4x4 with 170k miles. I replaced rotors, wheel bearings, ABS sensors on both sides, upper and lower ball joints, pads, etc. All parts are new OEM not the cheapest. I read the above post about bad (new) rotors but I did check the runout on each side and are in spec. Spindle nut is torqued to 16 ft lbs after backing off 1/4 turn per manual, wheel bearings pressed in to correct position, new shocks, spring mounts. The onlt remaining parts not replaced are pitman arm and tie rod ends which appear to be in spec. Am I missing something here?

Thanks in advance!

Is the shimmy felt only in the steering wheel, in the brake pedal, or both? If only in the steering wheel, then it's probably not rotors, but more likely a loose wheel, suspension component, or possibly even a crack in the frame.

If you notice it in the brake pedal, then chances are good it is an issue with either the rotor being warped or a piece of debris between the rotor and hub. How long ago did you replace the rotors? When you measured the runout, was that since the shimmy or when you put the new rotors on? Did you also check the rear rotors? One of the worst pulsations I ever experienced on a car was due to warped rear rotors (on a coworker's '97 Olds Aurora).

If you determine the problem is a warped rotor, then you will want to make sure you don't have a collapsed brake hose that is keeping the pads applied and generating a lot of heat. Does the Explorer seem to pull to one side when braking?

-Rod

The shimmy/vibration is felt through applying the brake pedal and a very sligh touch on the steering wheel. I did check all torques on rotor nut (load to 30 lb pounds, back off 1/4 turn and reload to 16 lb s), checked ball joints (all 4 are new), tie rods and pitman arm.

Frame is solid, whell lugs torqued to 100lb pounds per spec and the springs are seated correctly.

I checked the run out before putting the new pads on the new rotors.

ABS is working correctly with two new front wheel speed sensors. I checked the pulse rates for each wheel and they are correct.

Rear brakes are drum not discs and have new shoes springs, wheel cyclinders etc.

No pinched brake lines and the caliper seals and pistons move freely.

Wheel bearings inner and outer are new and packed with correct grease.

I replaced the trailing link arm bushings last year on both sides.

It shudders more than shimmy's if that helps but very little steering wheel movement.

Since you notice it mostly in the brake pedal, it's almost got to be from a warped rotor or drum. Something has got to be forcing brake fluid back into the brake lines/master cylinder setting up the pulse in the pedal.

I'm not familiar with the brake set up on the '94. Does the '94 have the manual locking hubs? It sounds like you're saying there is a nut that holds the rotor on, it doesn't just slip over the wheel studs of the hub. Is that correct? If it is the slip on type, then you will also want to make sure there is not some debris between the rotor and the hub. If this type has the rubber filled slide pins, make sure the pins are clean and lubricated as well.

Also, did you tighten the lugs in a star pattern without using an impact? I'm guessing that since you know to torque them properly, you also use the star pattern and avoid more than snugging them with the impact, but have to ask anyway.

-Rod

The 94 has the auto hubs and I did load the lugs in the star pattern using a torque wrench.

There is a 2 1/4 inch nut that spins up against the rotor with a small magnet key that slips between the nut and the spindle shaft

The caliper mounts using the two triangluar metal strips bonded with a vulcanized rubber with positive stops on each end.

I plan to take the rotors off again this weekend and take them to a machine shop just to make sure they are not distorted, then check all the fittings, bolts, nuts, tie rods etc once more.