Shaky wheel and vibration when braking - causes?

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Been dealing with a steering wheel shimmy as well as general shakiness under braking in the Taurus. Coming up on 80k with the original fronts, I figured it was time for a change. Knowing the brakes are a sore spot on the SHO, I picked up the Power Stop drilled/slotted kit for the fronts. Put it on a couple weeks ago and bedded them according to directions. Lately I've been having the steering wheel shimmy under light braking over 60. Also get some weird vibration felt in the seat of the pants too. Around town 100% perfect. Hard stops, mostly OK. Could the rear disks be causing some of it? Looking at them, I can see many (4-5) spots where the pads have deposited on the rotors from the parking brake (on this car it doesn't have the parking drum). What else could be causing this? Have heard sometimes it's suspension - bushings, tie rods, etc but she tracks straight and true and no funny noises over bumps or turns... Plan to pickup a dial indicator and check runout on the fronts to see if I have an issue there either from the flange (I did clean it) or a rotor defect. Anything else to check?
 
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Don't be so quick to write off suspension as being OK. I have had the same problems with the Audi for 80k miles, where at highway it shakes and shimmies and light brake application makes it worse but medium to hard braking it all goes away. Just had the tires road force balanced last night and that helped a litte, but the tech did test all the suspension and found one upper ball joint had some play. The tires balanced out well with little road force reading. With suspension, it takes someone with specific experience to see the small problems. Other indy shops have looked over my car and said everything was tight, but it took a seasoned Audi wrench to notice this platform specific problem. The C5 Audi always had trouble with front control arms by design.
 
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You haven't gotten any clicking from the front on turns? Rear pads aren't dragging? That's a big problem on Taurii/Explorers. FordTechMakuloco did a video on that, check it out.
 

itguy08

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Originally Posted By: threeputtpar
Don't be so quick to write off suspension as being OK. I have had the same problems with the Audi for 80k miles, where at highway it shakes and shimmies and light brake application makes it worse but medium to hard braking it all goes away.
I may have them look it over - have some light vibrations every once and a while but I've chalked it up to the poor PA roads. Wouldn't surprise me if it was suspension - the wife's Escape needed some front end work at about 80-90k due to our crummy roads.
Originally Posted By: michaelluscher
You haven't gotten any clicking from the front on turns? Rear pads aren't dragging? That's a big problem on Taurii/Explorers. FordTechMakuloco did a video on that, check it out.
No clicking that I know of and I drove with the windows down not too long ago. Rear pads did the drag thing - replaced at 55k or so. Down to the bare metal and needed rear rotors/pads/1 caliper. I'll have to take a look at his videos - he's got some good ones.
 
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Originally Posted By: tig1
Front rotors have excess run out. Replace.
That's a nice way of saying the rotors are warped. grin2
 
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Sounds like the brakes weren't bedded properly when installed. Try cleaning everything off and giving the rotors a quick scrub with sandpaper (nothing crazy.) When you re-install the pads google what the bedding practice is for your pads (usually higher speed stops, not complete stops) If that doesn't fix it you might need to replace the front brakes. Slotted rotors wear pretty quick but stop agressively. I would stick with a high quality (not high performance) or OEM for brakes
 
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Originally Posted By: itguy08
Plan to pickup a dial indicator and check runout on the fronts to see if I have an issue there either from the flange (I did clean it) or a rotor defect.
Check the run out first, if its out mark it and rotate the disk 180 and check again. If that doesn't bring it within spec calculate the difference and order a shim either from Rock or NAPA.
 
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Originally Posted By: Trav
Originally Posted By: itguy08
Plan to pickup a dial indicator and check runout on the fronts to see if I have an issue there either from the flange (I did clean it) or a rotor defect.
Check the run out first, if its out mark it and rotate the disk 180 and check again. If that doesn't bring it within spec calculate the difference and order a shim either from Rock or NAPA.
Just a note for the US readers Harbor Freight sells a runout gauge for $40, and RockAuto has runout correction plates, and there's a YouTube video of the procedure.
 

itguy08

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Originally Posted By: michaelluscher
Originally Posted By: Trav
Originally Posted By: itguy08
Plan to pickup a dial indicator and check runout on the fronts to see if I have an issue there either from the flange (I did clean it) or a rotor defect.
Check the run out first, if its out mark it and rotate the disk 180 and check again. If that doesn't bring it within spec calculate the difference and order a shim either from Rock or NAPA.
Just a note for the US readers Harbor Freight sells a runout gauge for $40, and RockAuto has runout correction plates, and there's a YouTube video of the procedure.
Funny you mention this... Stopped by Harbor freight and picked up the dial indicator on the way home. Will check into this Friday night or Saturday. Only thing that has me puzzled is moving it 180 degrees. From what I remember the Taurus only had one hole in the hub for the retaining screw. So I think I may have to go the correction plate or shim route.
 
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Just for reference. RockAuto has Raybestos correction plates. Does the SHO have bolts actually holding the rotors? Or is it like Honda's where they just put the screws there, but they aren't actually needed?
 

itguy08

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Originally Posted By: michaelluscher
Just for reference. RockAuto has Raybestos correction plates. Does the SHO have bolts actually holding the rotors? Or is it like Honda's where they just put the screws there, but they aren't actually needed?
Thanks. Yeah - there is one Torx bolt that holds the rotor in place. Not sure if it's needed but it was there so I put it back. smile Can't remember if they had multiple spots on the flange for them or not. I'll find out either tonight or tomorrow when I tear into them.
 

itguy08

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Thanks guys. Got out with the dial indicator tonight and found.... Driver's side runout .004+ (so bad I gave up) Passenger's side runout - .0015 or so. Pulled the driver's side, cleaned the flange a lot more aggressively and bolted it up and ended up with about .0015 in runout. Took it for a spin and seems to be 1000x better. Hard stops are quieter (but still noisy due to the drilled/slotted rotors) and the wheel is solid. There is still some vibrations at times but those are from the rear - those discs have pleny of markings from the parking brake pads. Next time I'm at the dealer I'll see what they charge to hit the rears with the lathe if it continues to be an issue. Or find a machine shop that will turn them - those are getting harder and harder to find.
 
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You don't need the screw on this car, it is there only for assy at the plant, you can safely discard it. Euro cars and cars that use bolts need it to hold the rotor in place when putting the wheels on.
 
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