My 2002 XK8 develops a rather annoying, usually mild vibration that increases with increasing speed... not at one resonance speed more indicative of an imbalanced tire. I have had all 4 tires balanced twice by two different shops, and they now are supposed to be perfectly balanced now. But, the shake/vibe still exists.

I can't believe Jaguar would call this normal. I realize a convertible body will develop "cowl-shake" over bumps, etc., but this shake comes and goes when traveling on a perfectly smooth interstate highway, especially above 55 mph. I would guess it is coming from the rear, because it is most noticeably felt in the seat, but there is a mild steering wheel shake as well.

When I had the rears balanced yesterday, and the car was on the lift, the technician said he could force a small amount of tire movement by gripping the top and bottom of the tire (loose camber), but he admitted to zero knowledge of the rather unorthodox rear suspension set-up. He suggested I take it to the dealer; so I resort to the collective intelligence of our Forum instead.

My guess is a bad bushing somewhere, but at only 39,000 miles I'm stumped.

Any ideas?

 

I've moved your question from General Tech Help section to XK8/XKR section.

What you describe is not normal. Members here will be able to advise on possible causes and solutions.

Graham

 

N875ED, You have not given us much to work with here. The usual questions are:

Have you "Road Force Balanced" these tires? Find a tire dealer with a late model Hunter machine.

What is the condition of the ties?

Any change in symptoms when rotating the tires?

Did your tire store check for bent wheels?

Most problems that you have described are tire/wheel related. Not all - but the first and smartest step is to eliminate tires/wheels before diving into the suspension.

Lastly- do a basic search on this forum. There must be at least a dozen threads on this topic. Some run for pages and pages. Are you a new boy?

And another last thing- stay with us. We need to know how it turns out for you.

 

+1
Hunter Road Force Balance

Probably a bent wheel, especially easy to bend if they are 18"+

You can "balance" a football but it will still shake when it rolls.

Make sure you get an experienced balance tech and explain the problem to them.
Vector

 

I have a similar problem, vibrations start around 100 km/h.

I have completely rebuild the front suspension, changing all bushes, ball joints, new brake pads and rotors ...

the vibration is there with two different sets of wheels.

And finally, I have the same symptom, the tire movement by gripping the top and bottom of the tire (loose camber). I identified the source of this, there is play in the differential output bearing.

Did you come across any solution?

I'm planing to do a rear suspension rebuild this winter, including rebuild of the diff, will see if that helps ...

 

Check the most likely, after wheels and tires, the rear shock lower bushing; then the rear wheel bearings, and finally the differential output bearing. Finally the upper shock bushings along with rear subframe doughnuts [bushings].

 

I posted this problem several months ago and have since replaced 6 tires and had them balanced 3 times...but I finally got the balance problem solved.

It appears this car is especially sensitive to "non-perfect" balance. After these several tries, the shop got the road force balance to around 12 lbs average for the 4 tires, and it is fine.

Moral of the story: Who does the balancing is very important, and it might take several tries to get it right.

 

Made friends, with the help of a couple of $$, with the tech at the local AAA service/repair shop. Had new Kuhmos mounted and balanced there. Car developed a shake at 70mph and got worse with speed. Tech, force balanced all 4 on warranty. Found last wheel to be a little bent. Put the new tire on spare rim which had original rubber from 15 years ago. Tech also checked alignment. No charge. Took car to a safe piece of highway (no troopers) Got her up to 105 mph no trouble. Jack