98 Lumina 3.1, 105,000 mi, brakes vibrate/shake sometimes when braking over 40mph

[rothermachine]

Would love some help or advice. Got a 98 Lumina, 106,000 miles on, well maintained, no problems. But in last few months, the brakes shake when coming to a stop from over 40 mph or so. Slowly been getting worse or more obvious. Can't get a read if it's doing when hot or cold.

Dad thought it'd be warped rotor(s). Took in to be turned, one was under specs easily (thought that was problem then), bought & installed new ones today.

STILL SHAKES, nothing violent, just enough to annoy/worry.

Pads on there were fine, at least 75% left on 'em. What could the next troubleshoot be???

THANKS!

[sysopt]

Thoroughly check suspension/steering for looseness, wear, etc.

[GMMerlin]

Originally Posted by rothermachine

Would love some help or advice. Got a 98 Lumina, 106,000 miles on, well maintained, no problems. But in last few months, the brakes shake when coming to a stop from over 40 mph or so. Slowly been getting worse or more obvious. Can't get a read if it's doing when hot or cold.

Dad thought it'd be warped rotor(s). Took in to be turned, one was under specs easily (thought that was problem then), bought & installed new ones today.

STILL SHAKES, nothing violent, just enough to annoy/worry.

Pads on there were fine, at least 75% left on 'em. What could the next troubleshoot be???

THANKS!

You say the brakes shake..do you feel this in the pedal, steering wheel or does the entire car shake?

[rothermachine]

I would say primarily in the brake pedal, I don't think a passenger would notice sitting in the car. Any ideas, since I just put in new rotors? Something in the brake pad assembly? It feels like something is out of round or the brakes are trying to grip something loose. Is funny cuz it dont happen all the time.

thanks for reading GMMerlin

Originally Posted by GMMerlin

You say the brakes shake..do you feel this in the pedal, steering wheel or does the entire car shake?

[rothermachine]

Originally Posted by sysopt

Thoroughly check suspension/steering for looseness, wear, etc.

OK, thanks for input. It doesnt seem to have any issues along this line. Handles like a dream around corners, etc., Suspension seems tight, nothing bouncy. But will mention to my Dad & my fav local mechanic when I call. But any other ideas would be welcomed

[JAL]

Originally Posted by rothermachine

OK, thanks for input. It doesnt seem to have any issues along this line. Handles like a dream around corners, etc., Suspension seems tight, nothing bouncy. But will mention to my Dad & my fav local mechanic when I call. But any other ideas would be welcomed

I had turbulence when braking hard. I drive very slow, so I rarely brake hard. As the turbulence worsened over several years, eventually even light braking produced severe turbulence. The best way to describe the turbulence is to imagine speeding down a highway that has a (small, pencil-thin) bump every carlength. This series of bumps would produce turbulence sounding and feeling like my braking. But the focal point of the turbulence was the left rear. So I replaced that one rotor, no change. Then I replaced that one hub (an easy job even for a car ignoramus like me) and the turbulence disappeared completely. The problem was a wornbearing, but my 1990 Lumina has permanently sealed bearings so I had to replace the entire hub ($120 from Pep -boys) in order to replace the bearing. I suppose the front hubs would be a lot more difficult, but I'm not sure.

[JAL]

I forgot to mention that inadequately greased caliper bolts have been known to cause such turbulence as well.

[GMMerlin]

Originally Posted by rothermachine

I would say primarily in the brake pedal, I don't think a passenger would notice sitting in the car. Any ideas, since I just put in new rotors? Something in the brake pad assembly? It feels like something is out of round or the brakes are trying to grip something loose. Is funny cuz it dont happen all the time.

thanks for reading GMMerlin

If you feel it in the brake pedal, that is usually and indication that there is a thickness variation in the rotor or a rear rotor/drum is out of round.
A good test for the rear drum is to drive about 10mph and slowly apply the parking brake until the shoes contact the drum..if you feel your vibration, then I would look towards the rear drums as the cause.