I was wondering what tire pressure people run in their XJs and how they found the drive. When I took delivery of mine, I never bothered to check. Found out later it was 42 psi all around.

Owners manual says 32psi for 20" and 39 psi for high speed. I lowered them to 35psi and will try 32 next week. It may be all in my head, but I think like the way it drove at 42psi better, even though the ride is softer at 35.

I have a SC XJ with 20" Dunlop SP Sport Maxx GT tires.

 

I run 32 psi, all around. 42 would produce a noticeably stiffer ride. If you like that, by all means do it but, it would only be necessary if you ran well in excess of 100 MPH for extended periods.

Albert

 

The 19" wheels on my XF are at 34. I correspond to the door sticker. It's a good balance and not too hard on the suspension.

Also, as the tires heat up, the psi rises along with it. At 42 cold would be high 40s after a few minutes of driving.

The 35 doen't sound too bad.

 

The 35 is definitely softer and quieter, but I did feel the car was more responsive in handling at 42. Will try 32 next week. I did find the low profile tires very sensitive to volume, which makes sense (PV=nRT) and will take note that I need to check more often as seasons change to maintain proper pressure.

My accutire digital gauge went a bit screwy on these tires, so I bought a Longacre racing one to get a more accurate reading.

I'd be curious how much softer the detuned suspension is in the 13 versus 12 model, bit I don't know of anyone with a 2012 SC close to me to compare.

 

I run the recommended 39PSI all around on my 2013 SuperSport/Speed and the car rides luxuriously firm and handles extremely well.

 

I have a supercharged XJ 2011 and put 35 on the front tires and 34 on the back tires. Above 37, the ride is too stiff. The setting is a god compromise between sportiveness, comfort and handling.

 

Well 32 is way different than 42.... No s**t Sherlock, right

As you longer term owners know, the car is very quiet and smooth at 32, maybe even more for the detuned 2013 model. The steering response is much at 42, as to be expected.

I think I will probably end up at 34 or 35 as a final setting. I'm not sure why the dealer inflated the tire to 42 and didn't tell me. That s beyond the manufacturer recommendations even for a SS

 

I run 2.5 bar (approx 36PSI) in the front, and 2.3 bar (33PSI) in the rear. I've historically run cars a little over the manufacturer-recommended pressures, as I like the improved tautness it brings, and I think manufacturers tend to under-pressure their cars.

With the XJ (Dunlop Sport Maxx GT J tyres on 20" wheels BTW), I find that the car really wanders around under braking with the tyres at the recommended pressures, so I run slightly over, even though it hardens the ride more than is ideal.

 

This is the 1st I heard of 42 psi. I stay 32 -35
at 42 excessive wear in the middle of all tires will be a big problem.

 

My car was just in the dealership for some warranty work which included a multi-point inspection. It was noted on the invoice that the tires were pressurized to 35 psi, per specs. It rides and handles just fine at 35 psi.

Dwayne

 

What was detuned? Do you have details, before and after?