Had a couple of odd feelings recently when cornering my 2008 XKR.

1) Sweeping left curve which is flat or maybe has a little adverse camber. About halfway round the car felt like it shifted over the rear suspension. It was a distinct shift, not a gradual change of attitude. There were no noticeable road joints or bumps to make the car skip, and it did not feel like that. The tyres felt planted. Did the active supension change settings in mid corner, or do I have a bushing or ball joint going home?

2) Tight right of about 120°. Got about 3/4 round and started to feed in throttle. The back end started feeling like the outside (left) rear wheel was oscillating in and out. Again, is something loose or was the grip on that piece of road less that I expected and I was at the threshold. It did not feel like I had that much lateral G going on.

I checked my tyres after both incidents and they are about 2PSI over spec. Any ideas?

Updated to say:

The shop cannot find anything wrong in the suspension. I went over the same tight right curve where I felt the shimmy in another vehicle and noticed two huge gouges in the road, typical of damage after a wreck. Of course, I was looking at the road surface more carefully this time. I am wondering if they were there when I got the wobbles and the outside tyre grabbed in them briefly.

 

What size wheels do you have and what brand/size tires are you running? Were the conditions wet/dry? Cool/hot? Was the road free of debris (dirt and gravel)? What was your speed in these turns?

 

Off the top of my head, this doesn't sound like tires. Bushings/bearings come to mind. My advice is to get the car inspected ASAP. How many miles on your car? After you get a "good to go" inspection report then you can look to the tires. Some tires are noteworthy for sudden breakaway characteristics.

Do keep us posted.

 

I agree that it is likely NOT the tires causing it.

Do a complete check of the rear suspension; check for wheel free-play by pulling and pushing on the mounted wheels when the car is raised. Check sway bar mountings, bushings, wheel bearings etc. Check the rear differential and drive shafts for end-play. Check all control arms and trailing arms for free play. Basically check every bolt, nut and bushings for free play. Makes sure the hidden upper mounting bolts and nuts for the dampers are tight.

Would not push or even drive the car at all until the issue is resolved.

Albert

 

Thanks for the comments.

To answer some questions:

The roads were bone dry in both cases (I cannot remember when it rained last) with no visible oil or gravel.

The car has 20" Sentas with the appropriate sized summer tyres, Hankooks front and Sumitomos rear.

Speed in the sweeping left was 50-55mph, and in the tight right probably 35-40mph.

Both incidents took place in the morning when the temperature was about 70-75°F, 21-24°C for our European readers. Mileage on the car is just under 25k.

 

Do you have the active diffy, wonder if it might be malfunctioning at times?

 

Did this happen near Area 51?

 

IIRC, the active diff did not arrive until 2010. Mine is a 2008.

 

You have different tires on the front and back. Surely this will cause the front to track differently than the rear and vice versa...

 

Sorry but I'm not buying that theory. Different construction tyres front to back can give odd sensations at initial turn-in; too soft at the front gives soggy steering and understeer while too soft at the back makes the car fell nervous as you turn in. In the case of the sweeping long left I had been in the turn for several seconds before I got the shifting sensation. I cannot see how tyres would do that as the car was in the steady state, not in transition.

A co-worker came up with a good analogy for what I felt. Imagine there was a large and heavy box in the back that slid slowly across the load floor due to the lateral G until it went clunk against the inside of the trunk. That "clunk" sensation was what I felt.

 

Ok, I have an update from the shop. See the 1st post.