Right rear still bouncing! GGRRR!

[Greg]

Hi All, I call on the awesome knowledge base of this great source.....please!

I posted about six months ago with this problem with some response and have gone to great lengths to diagnose with no luck.
Car in question, my baby, 1997 328ic with 104,000kms, sport package, front strut brace, '97 M3 offset rims 17x 7.5/8.5 with 225-45/245-40 but have also put the stock 16's on and same problem. I want to do alot more with time but not until I get this figured.

When the car is on a hoist and you spin it up to 100kms and up, the right rear wheel starts bouncing....alot! On the road it is getting down right uncomfortable and I'm the one slowing the hwy down now. I do keep right though!!

Today the tire shop, KAL TIRE! replaced the rears for excessive wear inside edges, lots of feathering....warranty! with all 4 corners aligned N/C!!!.... KAL TIRE! KAL Tire! (sorry to repeat that but they rock....n/c!)
Went to the hwy and still the same. When doing the alignment they could only say the rears were a bit saggy, enough that if you one handed the back end up a fraction, the green light lite up on the computer. Asked about H&R and Eibach springs and he said they would hinder alignment further by going lower.

What next? Could a rear half shaft bend or go out of balance? Why only shake the one side? To me that means unsprung weight. Trac control on or off, no change. Drive shaft? Diff? I had the centre bearing checked and OK, Brakes all good drives straight as and arrow or corners like magic

Any body out there heard of this and a remedy? Or where else to look?

My Speedo is in KMS, my brain is in mph.... I mean, an exit ramp marked 80kms does mean 80mph right?!!

 

[mjbst111]

yeah i would try a new half shaft. Maybe one of the cv joints is catching. Or if you don't want ot buy a new one switch the two see if the problem goes to the other side....

I assume they are the same on both sides.

 

[Kirby]

Have you checked/replaced the shock AND upper shock mount? That would be my very first suspect. Then examine ALL of the bushings for wear/rot (trailing arm, upper/lower control arms, subframe), make sure that all the bolts on the same are tight. If all those look good then check the half shaft/CVs.

I don't think the drive shaft is the problem, you would probably have different symptoms if it was that.

 

[Big Daddy]

I concur with Kirby on this one.

 

[mjbst111]

yeah it would be an expensive first try.

shock... if it was a bad and it bounces while up in the air, wouldn't the sway bar kind of prevent the bouncing as the shock would? There would have to be something causing the bouncing if its happening without the road's influence?

 

[Greg]

Thanks All, I have found an ex BMW guy with a shop who really wants to help diagnose. He seems to want the challenge. we will see. Today I am going to check the wheel bearing and CV joints. This is driving me crazy. With the new tires, I don't want to put too many miles on and take the chance of bad wear.

Sure glad I luv my ragtop. Saw a '97 M3 coupe yesterday close to a straight trade. I opted not to drive it 'cause I know me! I am done for if I find an E36 M3 cab!