On three occasions I accelerated my XKR at full throttle from slow roll to 60 and 75 MPH. Each time I felt a tail wag when it would shift up to the next gear, and that includes the shift at 60/65 or so. Now the road surface was good and dry in all cases. The wag requires a little driver input to keep the vehicle moving straight on. Is this the tires (295 - 20 -20) breifly losing traction? The car really scoots!

 

That's the tires breaking loose, or about to, and then the feel of the e-diff engaging to limit slip. Bit of a weird sensation. You may also see the stability control indicator flashing momentarily on the dash (squiggle lines) unless you have the DSC shut off.

I've experience this several times when pulling out to pass as a tire crosses over the painted line where grip is reduced. Blame the over-achieving engine with monsterous torque and the gearbox that conspires to vaporize the rear tires.

Bruce

 

I had the same thing, as described by Bruce, happen to me and my car is not an R. I was WOT on a slightly down hill access ramp and my first thought was that something broke.

 

Yes. A moment of silence for those poor rear tires. Especially the right one.

 

Yes, that confirms what I feel, the back end slightly skids to the......left I believe. At what speed/gear does this no longer occur on average dry pavement? It happened to me at about 65/70 MPH.

 

Grip, or lack thereof, depends on tire type, pressure and tread depth, as well as the temperature of both the pavement and the tires, and engine power is affected by octane, air density changes from altitude, ambient air temps and air/water intercooler coolant temps. I would be confident in saying I could spin my rears on "dry pavement" under some conditions to at least 71/75 MPH

Bruce

 

To the guys that have experienced the problem, I'd like to know what brand of tire are you using?

 

Mine are Pirelli and unlike the standard rear R 285, they are 295's on 10.5" wide Vulcan rims. Total miles on tires 1,000.

Peter