Steering wheel shakes-not rotors
08-07-2006, 07:26 AM
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Steering wheel shakes-not rotors Sometimes when driving at highway speeds light brake pressure will produce violent wheel shake. Usualy the first time the brakes are applied in a while. If I push harder it goes away. There is less with hotter brakes. I have gone over brake system completely. Car has only 20K . I've cut all rotors and changed to duralast pads . Then I put powerstop front rotors. I disabled ABS to be sure it wasn't ABS. Checked all front end parts,bled brakes and even torqued lugs. 1 thing that doesn't seem right to me is that as the car sits it seems like the front calipers relax. Shouldnt there always be slight pressure on the rotors? I think older master cylinders had 2lb check valves . Thanks 
08-07-2006, 10:02 AM
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Interesting. Sounds a lot like what I'm experiencing.
From reading here, I had figured I just had "warped" rotors, as the car didn't always do it, and I have made a few panic stops, and never performed any bed in process when I bought the car (first car I ever bought brand new, so the first car I ever had totally new brakes on).
I went ahead and ordered a new set of rotors and pads. Now you have me worried that that won't fix it. (but I can't complain too much, it's still an upgrade either way)
What I've found is that it's inconsistent, sometimes being worse than others. As if the brakes are grabbing inconsistently around the rotor, and that these extra grab sections are not lined up. When they are far apart, they shake the wheel badly, and when they are more lined up, they shake the wheel less so.
Just a theory, I have nothing solid to base it on.
I've not noticed heat to have any effect on the shake though. But I have seen that there is now some wheel shake just at 60mph or so. VERY little, but it's there. Not sure if it's the roads, the brakes, or just wheel balance. But, what's interesting is that this too wasn't there before. It appeared only have the brake shake got severe. (my car has about 7,100 miles on it)
From reading here, I had figured I just had "warped" rotors, as the car didn't always do it, and I have made a few panic stops, and never performed any bed in process when I bought the car (first car I ever bought brand new, so the first car I ever had totally new brakes on).
I went ahead and ordered a new set of rotors and pads. Now you have me worried that that won't fix it. (but I can't complain too much, it's still an upgrade either way)
What I've found is that it's inconsistent, sometimes being worse than others. As if the brakes are grabbing inconsistently around the rotor, and that these extra grab sections are not lined up. When they are far apart, they shake the wheel badly, and when they are more lined up, they shake the wheel less so.
Just a theory, I have nothing solid to base it on.
I've not noticed heat to have any effect on the shake though. But I have seen that there is now some wheel shake just at 60mph or so. VERY little, but it's there. Not sure if it's the roads, the brakes, or just wheel balance. But, what's interesting is that this too wasn't there before. It appeared only have the brake shake got severe. (my car has about 7,100 miles on it)
08-07-2006, 10:08 AM
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start examining your duralast pads, which unfortunately don't always have great consistency when it comes to a replacement pad. Also, have you flushed the brake fluid?
Just two questions to start with.
Just two questions to start with.
08-07-2006, 01:01 PM
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I said I had Duralast but I have Raybestos PG Plus (sorry). I have not flushed the system. I jacked up the car and spun my front tires. They spin with no pad contact. Is it possible that as I drive with no pad contact and step on the brake, the calipers vibrate until they stabilize in the bracket?
08-07-2006, 08:22 PM
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My tie rods are fine. The alignment feels fine but I will have it checked. Can anyone tell me about the rotor drag on your fronts without brakes pressed ? Thanks again
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08-08-2006, 01:08 AM
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There is some (cannot recall to what degree), however, I'd like to know what kind of driving you did soon after installation. From what you've descirbed, it's probably due to improper pad bed-in.
Also, even though your vehicle might have low miles, it's been around 4 years since the 4th Gen f-body was discontinued. Have you flushed the brake fluid properly? If you have flushed the brake fluid, did you use fluid from a brand new, unopened canister, or did you use some from a container that's been open longer than 1 month? Brake fluid is hygroscopic (meaning it absorbs moisture, some fluids better than others). Since you did bleed the system, did you properly reset the ABS module pistons? Improperly reset modules can trap air in the pistons.
Also, even though your vehicle might have low miles, it's been around 4 years since the 4th Gen f-body was discontinued. Have you flushed the brake fluid properly? If you have flushed the brake fluid, did you use fluid from a brand new, unopened canister, or did you use some from a container that's been open longer than 1 month? Brake fluid is hygroscopic (meaning it absorbs moisture, some fluids better than others). Since you did bleed the system, did you properly reset the ABS module pistons? Improperly reset modules can trap air in the pistons.
08-08-2006, 05:05 AM
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Thanks Foxxtron, I will definitly flush my system this weekend. I always break in pads and rotors slowly over hundreds of miles . I was not aware that ABS module pistons need reset. How is this done ? While bleeding brakes I did use new fluid from an unopened can being careful not to let master run low. I will also check my calipers again making sure one piston is not hanging alittle more than the others. Could my Procharger be causing this prob by disrupting vacuum to the booster? I have checked the check valve and it is working.
08-08-2006, 08:06 AM
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Originally Posted by DAVESS02
Have you checked your outter tie rod ends?
08-09-2006, 09:18 PM
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http://www.tirerack.com/brakes/tech/....jsp?techid=85
use this as a reference until you positively know what pads you will be installing. If they aren't any of the brand listed in the article, try to refer to the manufacturer's suggestion.
use this as a reference until you positively know what pads you will be installing. If they aren't any of the brand listed in the article, try to refer to the manufacturer's suggestion.
08-10-2006, 12:20 AM
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if you can't come up with anything. either put a dial indicator on the rotor(with lug nuts on) and spin it and make sure there is no run out on the rotors. if so, you may have to have those new rotors cut with a on the car brake lathe.
good luck.
good luck.
08-10-2006, 05:07 AM
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Alex, I did a run out check (.0005"). I have my car on stands right now so I can get right to work Sat. I spent an hour yesterday driving, trying to duplicate and exagerate the prob. It seems prob is worse if I were accelerating,lift then apply brake lightly. Maybe the vibration could be coming from the rear but transmiting to the wheel. I will be checking pinion angle, torque arm and all rearend components along fluid flush.
