vibration

[Tim LaWarre]

Gentelman, I have just installed new rotors and pads on my Benz,(420 SEL 1989) I have noticed a strong vibration at and aabove 65 MPH when braking. The vibration is not evident at lower speeds. Could it have something to do with the anti-lok system, should I disconnect the battery and reset the on board computor ?? The front end shakes and vibrates very bad when stopping on the expressway (due to a traffic snarl) Here in Florida the roads are pretty good especially the interstates. Does any one have any suggestions? All components are NEW

Thanks for your help

Tim

Tim,

Sounds like you have a warped rotor. Did you go with ATE? I have never had problems with ATE parts. It may be worth while to check rotors to confirm that they are "true" and reinstall....I know....a real PITA.

[stummala]

Did you check your brake support lines, clamps, and track rod bushings? How is your front suspension?

This is NOT caused by your anti-lock system.

Satish

[dpetryk]

Ive been there done that. Have the rotors turned or replaced. I have had the same vibration on both of my 420's. Warped rotors will definitely cause problems at high speed often not noticable at low speeds.

Where did you get the new rotors??
Take them back.

[Michael]

Forget turning them-once warped, it'll warp again. And you've lessened the amount of material the heat of braking can dissipate into, so don't go there-rotors are relatively cheap.

Did you clean the hub face before installing the rotors? I always clean the hub face with a wire brush attached to a drill, then coat it with a super-thin coat of hi-temp grease...makes future change-outs a breeze.

Hope this works out for you-we ALL hate to do the same job twice!

[Palangi]

Did this just start after the new parts were installed, or were the new parts installed to relieve the vibration?

If it just started when you had the work done, could it be that the wheel lug bolts are unevenly tightened, causing the rotors to warp?

Take each wheel off, rotate it 2 or 3 bolt holes, reinstall, and carefully torque the lug bolts down equally.

Cross your fingers and see what happens.

If it helps, wait a couple days, then loosen and retorque the lug bolts again. If it doesn't help, the rotors are probably bad.

[dpetryk]

I want to respond to Michael and Palangi.

Mike, I have turned the rotors on both of my 420's and it cured the problem. Bingo first time every time. The rotors are not really warped they are just dont have even thickness. Turning them will make them have even thickness. And it works. Yes it does remove a small amount of material but if you look at the percentage removed it is less than 5%. You would not be able to measure the difference in performance aspecially at normal levels. Im not talking about stops from 150MPH. Obviously he put new rotors on the car and look at what he got.

Palangi, as far at the lug nuts go I have observed the following to be true: The lug bolts on that car can no way exert any force on the rotors. The lug bolts are threaded into the hub for the bearings. The rotors are bolted onto that same hub with their own set of independant bolts. The rotor does not even touch the wheel in any way. So overtorquing the wheel bolts applies no additional force to the rotor. I have heard about over torquing lug bolts but I dont buy it, at least on this model. The idea that the torque on the lug bolts could warp the hub which in turn could warp the rotors at an impossibility in my opinion.

Correct me if I am wrong. I frequently am. But I need good eviedince that makes a solid case.

[suginami]

I say turn the rotors. I changed the rotors on my Nissan Quest, the G20, and my 93 300E. I used Brembo on the Nissan and the G20, and factory rotors on the MB.
I always take the new rotors to my local mechanic and have them turned before I install them.
I learned this from my father, who was a mechanic for Unocal (corporately, not a gas station, worked on drag racing cars, etc.) but our experience has almost always been that rotors are not true out of the box, even when brand name. I've argued with people and mechanics about it. Sometimes they even get a little hostile with me and refuse to do it. You know, sacreligious turning new rotors.
After seeing the rotors needed turning, they always apologize to me. Blows their mind.
I don't know why they can't make rotors absolutely true from the factory. I just know they don't.