940 non-turbo

Car shudder with shaking steering wheels at between 60-80 km/h speed. Took it to the wheel and tire shop. Advised to do a balancing job on wheels. No improvement. Then the suggested that rotor could be warped, so did both front rotor skimming. I'm not sure if this is the right term but what they did was having some kind of device attached to the rotor that sufaced the rotor as it turned. The idea was to even out the disc surface that was the cause for the shudder.

After that job that took about an hour, the "on the road" test came back with steering wheel still shakes (but with slight improvement). Those guys there told me to have the back rotor skimmed too as the remaining vibration is caused by warped back rotor. I argued that shudder in front so obviously has nothing to do with the back rotor. They explained that because the back rotors were tied to the axle that has no free play, the vibration is transferred to the front, and the only possible area that could release the vibration is through the steering wheel.

I had my doubt, and told them that I'll come back the next day because it was getting late.

So, is what was told facts or fictions merely to rip an ignorant soul like me?

Help, as I feel really unsafe driving in a shaky situation like mine. BTW I had the back caliper serviced for a stuck caliper recently.

Thanks as always

Laozong

I read all the replies to your post, and respectfully disagree with eliminating the rear rotors. I had similar problem, and after much doubt, turned out to be rear rotors. The front end shuddering and steering wheel vibration was so bad when braking, I thought my teeth would come loose. Replacing rear rotors, pads, and hardware eliminated the problem.

It can't hurt to do a "run out" on the rear rotors to eliminate them.

good luck

the ONLY way to be sure on the disks/wheels is to use a engineering dial guage on them to check the run out...anyone who does work without doing this is to be avoided....

you can buy a guage pretty cheaply and then lash up a suitable solid stand for it...

essentialy you mount the guage securely, plave the plunger against the wheel/disk and rotate the item...if its warped then the distance from the guage to the item changes, the plunger moves ina nd out and you can read the measurement on the guage...look for one that read 1/10000 of an inch...well worth the investment...

i would agree with other posters that IF its warped diskcs and you can see the wheel shake then its front end normally - IF its disks you should also feel it in the brake pedal at slow speed (comming to a gentle stop)

if you had a stuck caliper repalced didnt you replace the disks and pads on that axel as amatter of course anyway...if the calipers stuck the disk is almost certianly heat damaged and the pads should be replaced accross the whole axel anyway...

"Skimming" or resurfacing Volvo rotors is NOT recommended, as noted in the FAQ. They are cheap enough you just replace the entire rotor if needed. If the steering wheel shakes, then the fronts are at fault, not the rears. Out of balance conditions can be caused by:

-a tire tread separation or tire fault. Check this by rotating tires around the car or mounting the spare tire successively in place of each.
-bent wheel: ditto above advice
-worn conical bushings
-brake caliper dragging and warping the rotor. Since it shakes immediately after you resurfaced the rotor, I don't think this is it.
-bad rotors. I think you've eliminated this
-worn front end components (ball joints, tie rod ends)

Strongly suspect the bushings. Have the tires successively replaced with a known good tire.
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See the 700/900 FAQ under 'Select Link' button on the top right.

If you had a stuck caliper, it is possible that you warped a rotor, but you would feel that as pulsating in the brake pedal, you shouldn't feel that in the steering wheel.
a speed related shake is most likely tire balance, belt seperating, or bent wheel.
Have you checked the ball joints tire rod ends , wheel bearings and bushings for play? This couls easily be done at home. jack it up, set it on jack stands securly , and get under there and feel the different parts while a stout friend shakes the wheel on each side, look and feel for the slop.
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '92 Ford F350 diesel dually

tires being "out of round" would probably be all the time, not just braking. I've had that happen in many cars, I can't remember right now the fix...

bearing...bushing...??

I've replaced the rotors and had them turned. I wish I remember where I bought them new as they were only like $25 each and were OEM. The last turning took about an hour and cost about as much as new ones. Also, I'm not sure about your model/year, but the book says my weren't turnable. This has been debated some but after having them turned and paying for it I thought I would have been better off with new.

It's been my experience that if you feel a shimmy in the steering wheel while braking it's the front rotors. If you feel it in the seat, it's the rears.

Good Luck!

95' 964 162k

The entire steering wheel shakes. So should I take the car back to do the rear rotor as well?

Thanks for the response.

How are the bushings in the front end? Worn ones can cause problems similar to pulsating brakes.
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Norm Cook; Vancouver BC; 1989 745T 210,000KM

Did some bushing jobs in Dec 05. I'm not sure what names are those but bushings are the 4 conical shape ones, the 2 holding the stabilizing bar, the inner tie rod and one outer tie rod. Strut bars replaced in Nov 05 together with the strut mount.

The steering wheel was visibly shaking when brakes applied.

Thanks for the response

Laozong

I had significant shaking both during braking and hard cornering on our 1988 740- turned out to be a right front ball joint. With the 740/940 suspension design, it can be difficult to see whether a ball joint is bad- when you raise the car off the ground, the sway bar keeps the ball joint tight on the side you've jacked up.

Use a pry bar or large screwdriver to press against the ball joints to check for any looseness.

I would also ask to have the shop that balanced the tires spin them again on their balance machine. Possibly there is a bent wheel or a failure in the tire itself- a broken or shifted radial belt inside the tire. However I think this would show up at all times, not just when braking.

Good luck!
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Rob Bareiss, New London CT ::: Roterande Flakt Och Drivremmar!