vibration during braking - rotors?

[mikedev10]

hey guys, when i'm braking i get some vibration from the car which can be pretty violent. if i apply more pressure though the shaking goes away. does this mean that my rotors are warped?

if so, suggestions on where to get stock/good rotors/pads for cheap appreciated! i browsed alloembmwparts.com and there were a bunch of similarly priced brake pads, not sure if any are better than the pack? thanks for any info!

[tim]

It certainly sounds like a warped rotor. Do you notice any unusual syptoms when not braking? What do mean by violent? I'm picturing you getting thrown around the passenger compartment- and if that's the case, there's more to it than just rotors. Your calipers may be off spec. or worse.

The oem rotors and pads are decent and reasonably priced just about anywhere except the dealer. You could get the cross drilled ones for not much more.

If you want to upgrade- check out Bruno's faq on the subject. If you've never done it before, let someone do the work for you. Should be about 2 units of labor. Many good indies will let you supply your own parts.

[632 Regal]

what speeds are the fronts shaking? If around 45-55 mph its most likely the thrust arm bushings. If at all speeds then possibly rotors.

[John B.]

I had a similar problem recently & it turned out to be the ball joint on one of my thrust arms. Check for wear there before buying rotors. Do you get any frt end clunking noises over low speed bumps?

[spddmn713]

I am having the same problem with my car, and I am just wondering do you need to replace the thrust arms or can I just replace the bushings?

[632 Regal]

you can try to replace the bushings as they wear at about 2x the miles as the ball joints, If you dont know the history of them then replace the whole unit with the arms that have the 750 bushing pressed in.

[John B.]

I am having the same problem with my car, and I am just wondering do you need to replace the thrust arms or can I just replace the bushings?


I would replace the entire unit as I doubt you're going to replace the bushings without pulling the entire arm off the car anyways. By the time you break the ball joint free I wouldn't want to reuse it. I had no shimmy, only the clunking and brake vibes so I doubt my bushings were the problem but I was happy to update to the 750il bushings. I would highly recommend renting the thrust arm press from KMS as it makes what can be an ugly job with a pickle fork a 2 minute procedure.

[spddmn713]

Thanks! That answered my question.

[Bill R.]

remove it and it only requires that you take off 4 more bolts. Plus you can inspect the other ball joint for play while its off the car. Remove the 3 bolts that hold the strut to the steering knuckle and the 2 bolts that hold the thrust arm and the lower control arm http://www.bimmernut.com/~billr/images/Thrustarms/lowercontrolarmunbolted%20copy.jpg http://www.bimmernut.com/~billr/images/Thrustarms/strutboltscopy.jpg http://www.bimmernut.com/~billr/images/Thrustarms/Thrustarmonsockets1%20copy.jpg http://www.bimmernut.com/~billr/images/Thrustarms/socketstaremoval%20copy.jpg

[632 Regal]

pretty dirty 3lb'er there!

Id suggest a nut on that balljoint if you may plan on re-using it again.

Beautiful pictures Bill!

[mikedev10]

it seems to happen at all speeds, just dependent on pressure. lot more noticeable at slowing down from 50 or so though. i don't notice any clunking noise or bumps at low speed. so you guys are saying ball joints + thrust arms + 750il bushings ? good time to install those racing dynamics sway bars i have sitting in the garage too huh??

[John B.]

it seems to happen at all speeds, just dependent on pressure. lot more noticeable at slowing down from 50 or so though. i don't notice any clunking noise or bumps at low speed. so you guys are saying ball joints + thrust arms + 750il bushings ? good time to install those racing dynamics sway bars i have sitting in the garage too huh??

If your ball joint was shot like mine was you'd have the clunking. Check your rotors for run out as they may be warped. Don't buy anything until you KNOW what the problem is.

[mikedev10]

what is run out? how can i tell if the rotors are warped? even with the wheels off unless they are blatantly warped i don't think i'd be able to tell by just assessing with a visual scan...

[tim]

run out- a big lip on the outer edge of the rotor. It is an indication of how much material has been worn away where the shoes contact the rotor. If you've worn away alot of material, they're more likely to warp. Just look at them from through the wheel or take the wheels off and get a good look.

Also, if you don't have the clunk or the shimmy, I'd hold off on assuming the thrust arm ball joint is shot. Could just be rotors and maybe a bad caliper.

[mikedev10]

how much is "big" ?

i don't mind changing the pads/brakes or the arms/bushings too much, since i plan on autocrossing it once it's nicer outside than the 0 degree weather we have now!!

[632 Regal]

big would be as thick as a paperclip.