I recently replaced all 4 tyres, the front inners were shot due to lower arm bush wear and the rears were wearing prematurely in the middle despite being run at lower than spec pressure.


With this set I plan to keep an eye on tyre depths for early warning signs, so am taking 3 measurements per tyre (outer. mid and inner) every 1000 miles or so.


This set of rears are at 2bar vs a sec value of 2.2bar but are already starting to wear in the middle.


What pressure are you using in your rears, mine are 19inch.

 

My wife's 2006 XK8's rear tires are 255/40/19. When we purchased the car in early February 2012, the lousy Pirelli P-Zero rear tires were close to being done with just 15,000 to 16,000 miles on them. I noticed the excessive center wear the first day we had the car in our possession. I replaced the rear tires with new Yokohama YK580 tires in April 2012. Started them at 32 psi. Noticed that the excessive center wear continued. Backed them down to 30 psi. The center wear lessened but was still present. Saw a thread here on the forum stating that many long-time XK8 owners were running their rear tires at 28 to 29 psi. I followed suit and the dreaded center wear finally stopped and the tires began to wear evenly. Since then I have kept the rear tires at 28 to 29 psi year-round. I've never intentionally run tires that low in my life but with these XK8 rear tires, you have to in order to achieve even treadwear....

Her 245/40/19 front tires have always worn evenly at 32 to 33 psi, so that's where I keep them....

 

My rears are 18's, but were experiencing the same wear. I have started running them at 29psi, but I think it is too late to save them now. Outside tread is normal wear.

I will need to replace them soon, so will be interested in your findings.

 

Same as Jon, on my 2004 with 18's I have been running 29 psi on the rear with excellent results. Fronts I run at 30. Whenever I go for an oil change and forget to tell them to leave the pressures alone they always pump them up to 33, and the ride it terrible, it's as if I am driving on a washboard.

 

BTW, I'm a stats guy, and I love your graphs!

 

There are two variables at work here; the tires and the pressure gauge. I would suggest that unless you paid more than $30 for your gauge it is not accurate to within 10% and that's 3psi. Every tire has its own preferred perfect pressure.

I 'read' the tread contact with the road by observing the dust contact area on the tires and raise/lower the pressure to get max contact with a gauge dedicated to that car. In the case of the current car, current tires and dedicated gauge that is 28psi.

 

Very good point about tire gauges. They do indeed vary in quality. My current digital gauge (about 4 years old now) has always been within 1 psi of the better gauges used at the tire shops I have frequented. I think I paid about $15 for it on sale at NAPA. That's been good enough for my purposes....

The toughest factor in my neck of the woods this time of year is that it can be 25 degrees outside at 7:00 am and 55 degrees outside at 3:00 pm. That's a considerable temperature swing that can definitely raise your tire pressures by 2 to 3 psi. I'm pretty **** about all of our tires but I just don't have the time or inclination to adjust the pressures multiple times per day, every day, due to the current weather conditions....

 

Thanks guys for your comments, so I am running at 2bar (29PSI) (checked with two gauges)and still getting premature wear, I could drop it another 1 psi but then I'm going to be well under the recommended pressure and will have poorer fuel economy as a result.


I'm now starting to think about the equation for inflation pressure/fuel economy/tyre life/tyre cost, there will be a point where it will be cheaper to keep the pressure up and change the tyre more frequently than to optimise the life of the tyre.

 

Have you had the rear tow in checked recently? Not sure, but that is often flagged as a cause of excessive wear.

 

This is a little information on my tire pressure issues years ago. Link Tire Pressure I have since gone back to air and not Nitro out of convenience. I continue to check the depth of the tires and pressure in hopes the tires will last a little longer and they have so far.

 

Here is an update, fronts at 2.4bar and the rears at 2.0.

Time to check my toe in as the front outers have taken a bit of a dive.

 

Here is another update, the fronts are doing well but the rears have taken a real dive in the middle of the tyre, the legal limit is l.6mm so I am pretty close to that.


I wonder if a premium brand will do any better.


I started noting the data a few months after the rears were put on, so I think they have lasted about 12kto 14k miles.