So a brief story of where I am with my 02 XJR:

It was in the shop yesterday because the front end is all over the road. Any kind of grooves in the road and whichever tire hits it will move quickly in that direction. I chalked it up to a bad sway bar bushing or possibly a lower control arm bushing. No big deal. At the shop, I was told all the bushings were in excellent condition and that the likely culprit is the tires. They are BF Goodrich G-Force tires which came on the car when I bought it and I had previously had those on an 05 S4 and absolutely loved them. The steering wheel used to shake lightly around 50MPH, but nothing serious. When I first bought the car, I blew out the front passenger tire on a really nice pothole on the 5 freeway and replaced that tire and had the alignment done. My mechanic also suggested that the brand new tire might be throwing things off up front so he rotated all my tires. Now (Aside from the flat tire I had this morning) the steering wheel shakes pretty bad at 50MPH. Plus or minus about 5MPH it goes away. Since he seems pretty confident that the front end is tight, my only thought was maybe it was a tire out of balance, but with the rotation it would suggest that all 4 tires would probably be out of balance which seems unlikely, but not out of the question.

Anyone ever heard of anything like this? The moving around I don't like, but if it is the tires, so be it, but the shaking is definitely something else. I'm going to go to a tire shop later to get that tire patched and I'll probably ask them their thoughts, but I always like to go in prepared...

Just for clarification...the tires pressure are spot on and the wheel doesn't shake under braking - eliminating warped rotors...

Thanks in advance and Happy Holidays,
Jon

 

Jon:
The condition you describe is called tramlining and it can be especially noticeable on our XJRs. Apparently the tire size and steering geometry causes it. Check the archives for tramlining.

As I recall, my G-Fores were pretty bad for it. I have Sumitomas now, and they are a good bit better.

The shake is either the balance or an out of round tire. Out of round can mean rolling dimension, meaning that it might look round but distorts under load, which can also lead to tramlining. A ply separation might be happenning, which can lead to a very exciting driving experience!
Good luck and let us know what you find.

 

+1 on Sparkenzaps comments....beat me to it...lol

Its more or less exactly what I would have said myself.

I have an Audi A6 which used to run 225x17's and never really had any issues tramlining......I upgraded to 255x19's and now its prone to it

 

+1

I've had the shimmy at 50, turned out a rim had shed a wheel weight. A quick way to confirm is swap the rears to the front and see if it makes any difference. But you're taking to the tyre shop so this will get sorted.

You might have a bent/egged rim with the pothole.

These cars require an Asymmetric tread design.
They HATE these...


And LOVE these...



Fitting assym patterns almost gets rid of all wonder, to give a more sporting direct feel.

 

Thanks guys. I searched the forum for "tramlining" and it seems like a common issue. Pity I didn't know about it when I blew that first tire out or I would have just replaced the front two with Asymmetric tires as suggested.

Sean - The mechanic that looked at the car yesterday did swap out the wheels front to back so the newest tire is now on the back. Seems to me the shaking got worse. I don't think it's alignment and apparently not bushings so, in my limited knowledge, I can only imagine it's a wheel weight, but now it would be two wheel weights....

Hopefully it can get sorted out later...

 

could warped rotors cause this condition? or is it always the tires or balancing etc?

 

I've been having this happen recently too. Thanks to all I'll check the balance on all tires now.

 

Unlikely - warped rotors / discs would be suspected if this issue heppened only when braking

 

My mechanic suggested a worn out front wheel bearing could cause that vibration too.
What do you all think of his statement? I'm a bit sceptic about that even if I trust him completely otherwise.

Cheers,

David

 

Won't be warped rotors - they give you the shakes when braking.

Would suggest Dynamic Balancing (wheels on the vehicle) and check for either/or/both buckled wheel (it doesn't have to be much), tyre with an internal ply fracture. Since you hit a pretty bad pothole with the front, the rear tyre on the same side would have taken quite a 'belt' at the same time. The bounce of the car when you hit with the front could have taken a lot of the 'sting' out the rear impact, but still have damaged the rear tyre enough to cause it to develop a bulge as the centrifugal force develops under increasing rotational speed. And since you have rotated the tyres, it's quite poissible that you now have a crook tyre on the front. Not a pleasant thought, I prefer any blowouts to occur behind me.
Personally, look back at the original manufacturers specs for tyres, (likely Michelin) and stick to that brand. I don't know the Goodyears, but I would doubt that they come close to the kind of spec that a Jag Tyre would call for.

cheers,
Languid