thanks for the advice my Jaguar bretheren

Just having a read and according to the Repair Operations Manual, the original spec for mine is actually 205/70. Damn thats paper thin!

But I noticed also it states for normal use up to 193 km/hr (120 mph)with one passenger and 27kg (60lb) of luggage the tyres should be 26 PSI in the front and 24 PSI in the rear.

i checked mine the other day and they were around 28 but that was after they had been running, so i think i might invest in one of those little pressure gauges and check it in the garage.

Im make sure at Bob Jane they inflate them/deflate them to spec on Friday.

+ =

 

guys, a curve ball for you.
those with older XJSes with 15" wheels who want the 'classic' look, check out Blockley Tyres of UK.

Click on link, and scroll down past vintage tyres to the bottom of the page..

Blockley Tyre - Vintage Racing Tyres

 

Guys help me out here. Im just sitting in the tyre mart waiting for my new P600 to be fitted and I mentioned to them the spec for inflation which for mine as discussed is 26 psi front 24 psi rear.

The gentlemen behind the counter recommend against that low a pressure as he stated the vehicle was quite heavy. I think he just mentioned he would recommend 38psi.

I trusted his judgment as he was the expert, what do you guys think?

 

I'm not 'one of the guys' but I'll tell you what I think.

I would *Never* run 24 pounds in rear tires on anything I have ever owned except for the lawn tractor. Tires on my car are kept at 35 pounds front and rear. Anything much less than that on such a heavy car is asking for disaster, not to mention sluggish steering and handling.
(';')

 

Thanks mate I appreciate the reply.

Yes I thought she seemed quite low but it is in the spec.

What are the advantages/disadvantages of running at these spec pressures?

Could it be that tyre technology back then was different?

 

Just remember that Jaguar tested the tires and wheel combinations before they put it in print. The tire store has not done any high speed testing or run it on skid pad. Tires gain PSI when driven. It is the PSI that provides the footprint for any given tire size to support the car's weight. Too much and you run on the center of the tire with less sq. in. of rubber on the ground. Too little and the center lifts as the side takes on the weight. Ever notice that race cars warm the tires so they have the right pressure and foot print right from the start of a race. I'm not a tire and suspension engineer so I leave it up to the designers that are...yes sometimes they come up with a better design after they have released a product, like going from 15" to 16" to 17" to ect ect...

 

I don't know about tire technology in the past Century, but this is what happens by having low tire pressure (even unknowingly) and then driving with Great Enthusiasm:
(';')

 

The XJ sedans and XJSs weigh in at about 4000 pounds, give or take, so, while not featherweight class, they're not obnoxiously heavy.

I generally run 34/34 or so myself as it feels like a good compromise to me. However high-20s or low-30s wouldn't be asking for disaster....for moderate speed driving with a light load. You'd have a softer ride and, as you say, softer steering.

Cheers
DD

 

thanks guys i appreciate the input.

 

tyre shop guys in NZ always recommend a few more PSI than the handbook. For better wear.
Some cynics say manufacturers say a bit soft for comfort, so their new model seems luxurious.
I go for mid-30s for all 3 vehicles, all weigh about 1800-2000kg unladen.
I have done trackdays in my car and checked pressures after 10 fast laps. pressures, get way high when hot..

 

Interesting

I was tinkering in the glove compartment and found a little sticker that says "Mirror" with an arrow pointing to it. I hadnt noticed it before

So when you flip up the mirror it has the sticker for the wheel pressures and all.

And this is what it says, but note it is for 215/70's.

 

235-60-16 eagles on rear & 225-55-16zr u/royals rain tyres