shaking at speed not identified

[resunoiz]

THE BACKGROUND

320ci vert, I bought the car in december. It was stopped for 10 years in a shed, and came back to the street in the same days.

I had 17" wheels on with summer tires. Low quality but brand new. I had a vibration on the steering when braking that a balancing could "cure". I didn't notice any other vibration, maybe because the car was "new" for me.

I mounted 16" wheels with winter tires and went with them till april. Then I mounted back my 17" wheels after balancing. No vibration at braking, but a costant vibration at 60kmh and 110kmh. VERY INTENSE vibration on the REAR wheels. I can feel it on my back, steering is solid and doesn't vibrate at all.

Here's my troubleshooting sequence:

1) WHEELS

- checked all 17" wheels straightness, all ok;

- tried 4 different 17" tires from another car, same issue;

- inverted front and rear tires/wheels, same issue;

- put back 16" wheels: vibration still present but less evident . that's why I didn't noticed it a lot before putting back 17";

- checked wheels turning on the balancing machine and on the car itself, straight as hell;

at that time, I could exclude tires.

2) DRIVING CONDITIONS

- the vibration is very evident between 55/60kmh and 110/120kmh;

- at the very starting of the car (20kmh for example) the vibration is present, but less noticeable maybe due to torque;

- the vibration is the same with EVERY gear and WITHOUT gear, in straight street or in turns. It is only speed dipendent so I can eclude engine bushings (quite new)

3) MECHANICAL

- changed driveshaft front support, even if it was quite new;

- revised main driveshaft sviwel joints/bearings;

- checked back main driveshaft alignment;

- verified there was oil in differential;

- verified there was lubrification in right/left driveshafts.


The vibration is still there. At this point, I'm clueless. I don't know what other to check (and how) and stop wasting money. Suggestions? What other components can cause that vibration?

[johnjmurray]

Rear shocks/mounts? Rear control arm bushings? Rear subframe cracks? 10 years of inactivity is enormous. Stuff deteriorates. I think the taller tire sidewall on the 16's masked the issue.

[resunoiz]

is this someting I can check by myslef, wiithout blind-changing parts?
I'll check subframe soon, but I have no noises.

[dhurley34]

Sticking brake caliper?

[KlausH79]

I had the exact same issue albeit with my Skoda station wagon, but the cure? New tires. First the problem was with the old winter tires (8 year old Yokohamas), then updated to new Goodyear’s. Then came summer and semi new Hankooks summer tires went on. Vibration at the same speeds, updated to new Goodyear summer tires. Problem solved...again.
I’d try a set of new good quality tires. Any chance you can try on someone else’s tires just to be sure?


Sent from my iPhone using Tapatalk

[resunoiz]

Sticking brake caliper?

Wheels seems to turn with no effort and/or noise, so I assume the aren't. Can you suggest something to check it out?

I had the exact same issue albeit with my Skoda station wagon, but the cure? New tires. First the problem was with the old winter tires (8 year old Yokohamas), then updated to new Goodyear’s. Then came summer and semi new Hankooks summer tires went on. Vibration at the same speeds, updated to new Goodyear summer tires. Problem solved...again.
I’d try a set of new good quality tires. Any chance you can try on someone else’s tires just to be sure?

read first post: i tried with THREE sets of wheels/tires.

my 17! are brand new and aligned, the other 17" wheels were worn but had exactyl same issues, the 16" wheels and tires are brand new. All of them present the same behaviour, less evident in 16" due to higher tires but present.