car shakes when braked

[rober]

Hi,

Would someone please give me some ideas why my car shakes every time I apply brakes? Thank you.
I have a 96 Lumina, 3.1, sedan. I just replaced new front tires.

[Manny_boy]

From your description, it sounds like parallelism. Your front brake rotors are warped, and need to be resurfaced, or replaced.

[jeffcoslacker]

Originally Posted by Manny_boy

From your description, it sounds like parallelism. Your front brake rotors are warped, and need to be resurfaced, or replaced.

You are right, but the fact of "I just replaced the front tires" leads me to believe that the shop did not torque the lugnuts correctly. Lumina's are especially sensitve to this, esp with alloy wheels. Uneven torque will cause instant rotor distortion and "shake n' brake"

Loosen all the lugnuts, then torque them carefully to 100 ft/lbs. The problem will go away.

[Manny_boy]

Originally Posted by jeffcoslacker

"shake n' brake"

you guys crack me up

[paulfischer]

on my 99 LTZ I have a plastic bushing / sleeve/ guide (whatever you want to call it) that goes into the caliper for the mounting bolts.
They do wear out, and when worn, it will cause the car vibrate a little when braking. So I change those whenever I do a brake job.
Also had a 96 grandprix that had them. So maybe they are common on the GM cars.

[jeffcoslacker]

Originally Posted by paulfischer

on my 99 LTZ I have a plastic bushing / sleeve/ guide (whatever you want to call it) that goes into the caliper for the mounting bolts.
They do wear out, and when worn, it will cause the car vibrate a little when braking. So I change those whenever I do a brake job.
Also had a 96 grandprix that had them. So maybe they are common on the GM cars.

It's not a bad idea to replace caliper hardware like that if it is anything but in perfect condition. Worn bushings and bent or distorted hardware or mounting bolts can really cause some strange problems.

Equally important to put Syl-Glide or some other high-temp lubricant/protectant on all moving parts and contact surfaces. After the caliper is installed, but before pumping it up to seat the pads, the caliper should slide easily and smoothly back and forth on its mounts with one hand. If not, there's something hanging.

[richtazz]

I'd put my money on improper lug nut torque also, parts swapper monkeys don't know how to use torque wrenches.

[rober]

Thanks all for the inputs. I replaced brake pads, and retorque the lug nuts, but the car still shakes a little when I try to slow down from 60 mph.

[paulfischer]

Originally Posted by rober

Thanks all for the inputs. I replaced brake pads, and retorque the lug nuts, but the car still shakes a little when I try to slow down from 60 mph.

Do you feel the shake in the brake pedal?
Maybe a wheel out of balance? Try replacing those plastic bushings.