: Vibrations/Shaking under slight braking



JFensty
12-21-10, 03:33 PM
On occasion I get a heavy shaking/ vibration in the front end and steering wheel when lightly applying the brakes to scrub off a few mph. Usually from 70 - 80 mph to 50 - 60 mph. It only does this when they are nice and warm. (Lots of curvy roads up here). The harder I mash the pedal the less it shakes.

I've had the car for approx 3 months and it did this when I first purchased it. I replaced the rotors and pads (ceramic) and it still would shake every now and again but mostly stopped. I burnished the rotors just as posted in the faqs and even lightly sanded the pads and rotors and burnished again when the shake was still there.

I do have a slight bump noise when speed bumps are taken at angles, not straight on. I figured this was end links. I have checked all of the bolts on front struts, no leaking either.

Any ideas on what is causing this? Could it possibly be rear rotors or maybe something wrong with the calipers? . Is there any special way to bleed these I am unaware of?

Thanks,
Jerry

AG'S-V
12-21-10, 03:36 PM
Had your tires/wheels balanced?

Does it go away or do it all the time?

JFensty
12-21-10, 04:15 PM
Tires not balanced lately. It doesn't happen all of the time. Hasn't done it for over a month then took some windy roads over the weekend and got brakes fairly warmed up(more than normal) and it came back. Now today its not doing it again.

Fasciaguy
12-21-10, 05:03 PM
Jerry I doubt very much if it has anything to do with your calipers. My guess would be the rotors and for as many times as you have taken the wheel on and off might explain some of the variation your seeing. Please dont take this advice as condescending as most people know how to install a wheel but over tightening one side of lugnuts before they are all snug can cause a very slight warp in the rotor giving you a vibration feel in the steering wheel. Try to losen the lugs and carefully re-tighten in the star pattern making a couple rounds and not torque all down in one pass. Oh and just because they are new rotors doesnt mean they were heat treated properly and could have a warp epecially if you did some hard braking before the new pads were seated.
This may help and if not I would check wheel balance.

kevm14
12-21-10, 05:54 PM
Mine has these symptoms, and I also have worn sway bar bushings. But I don't think the bushings have anything to do with it. My rotors are drilled aftermarket (not necessarily cheapies, but I did not buy them). My tires have some miles on them so I am hoping next wheel balance will take care of it as I believe I feel a shake in the wheel without being on the brakes at all. Getting on the brakes lightly seems to make it worse then a harder application and it goes away like you describe.

JFensty
12-21-10, 07:54 PM
Jerry I doubt very much if it has anything to do with your calipers. My guess would be the rotors and for as many times as you have taken the wheel on and off might explain some of the variation your seeing. Please dont take this advice as condescending as most people know how to install a wheel but over tightening one side of lugnuts before they are all snug can cause a very slight warp in the rotor giving you a vibration feel in the steering wheel. Try to losen the lugs and carefully re-tighten in the star pattern making a couple rounds and not torque all down in one pass. Oh and just because they are new rotors doesnt mean they were heat treated properly and could have a warp epecially if you did some hard braking before the new pads were seated.
This may help and if not I would check wheel balance.

Only slightly condescending..LOL.. I always use a wrench to manually tighten lugs. I don't think it is the rotors, due to the fact that it is only when they are very warm. With the outside temps in the 20's I have to lean on them hard for them to start the shaking. Normal driving and they usually are fine, no shake.

There aren't many parts on the front that would cause the shakey shakey... not sure its tires either since I have rotated and changed pressures. The sway bar bushings look to be in good condition just the end links possibly.

Black Sunshine
12-21-10, 08:12 PM
My GM "performance drilled" rotors w/ ceramic pads are about toast and producing this symptom. Warped. Easy to understand after 130,000 miles and few cycles on the lathe. Always remember NEVER lock down the parking brake immediately after give the brakes a big workout. They'll warp easily at the track.

Been my experience that there are different kinds of "shake". If it's a bouncing shake it's probably balance/tires/wheel. If it's a lateral shake it's might be alignment/steering. (If the steering wheel is hummin' under acceleration it's my headers hittin the steering column cause my crap for GM engine mounts are dead (CS mounts waiting on the shop bench):duh:.)

High speed (90 mph) on-car balancing is the ONLY way to go if you do a lot of highway miles. Marking the wheels/studs to maintain position if ya gotta pull them. IMHO, well worth the money and won't drive without it.

JFensty
12-21-10, 08:19 PM
My GM "performance drilled" rotors w/ ceramic pads are about toast and producing this symptom. Warped. Easy to understand after 130,000 miles and few cycles on the lathe. Always remember NEVER lock down the parking brake immediately after give the brakes a big workout. They'll warp easily at the track.

Been my experience that there are different kinds of "shake". If it's a bouncing shake it's probably balance/tires/wheel. If it's a lateral shake it's might be alignment/steering. (If the steering wheel is hummin' under acceleration it's my headers hittin the steering column cause my crap for GM engine mounts are dead (CS mounts waiting on the shop bench):duh:.)

High speed (90 mph) on-car balancing is the ONLY way to go if you do a lot of highway miles. Marking the wheels/studs to maintain position if ya gotta pull them. IMHO, well worth the money and won't drive without it.

You still in Moultrie? My parents live in Valdosta. I was down there two weeks ago. Anyway the rotors have only 4000 miles or less and car has not been tracked. Basically I get a shake that makes the steering wheel go back and forth an inch or so. Not as bad to shake it out of your hands or to lose control. It does have a rhythm to it that I think an alignment problem would not cause.

kevm14
12-21-10, 09:28 PM
Does it ever do it without touching the brakes?

JFensty
12-21-10, 09:56 PM
No only when light pressure is applied is when its at its worst. Gets better the more pedal pressure.

JFensty
12-21-10, 09:57 PM
Could it possibly be a wheel bearing? Trying to figure out how the brake temp would matter.

CadzillaTN
12-21-10, 10:54 PM
Road force balance, 40 bucks. Can't hurt and it will certainly rule out tires as a source. Look for a low score for each tire.
12 or under was considered a good tire by the dealer when they suggested my (cheap) tires were causing vibes in my trans.. they were all under 5..

Make sure you check around, quality of the job can be drastically different. A good tire tech could spent 8 hours balancing 4 tires if he wanted to, dialing them in to be smooth at various speeds. Obviously they won't because job doesn't pay them much, so don't go when the place is packed.

JFensty
12-22-10, 08:52 AM
Thanks. I'll check into it.