That's probably what I'll run after I get the Michelins on next week.

 

Finally going to pick my car up... 02 XK8 Conv... 245/45/18, 255/45/18

The mechanic who has been taking care of everything recommended I drop the pressure to 28/30 instead of 30/32 for a "softer" ride with less shimmy and the feel of each and every bump...

I'm not looking for leading edge performance, so I'm thinking that will make sense... plus they should last longer.

Thought I had the stock 17's... gotta change my sig block...

DJ

 

Just watch your tire wear. Lots of threads about excess wear on inside/outside of tires depending on whether over or under inflated. You're in the ballpark, so just check them once and awhile. These cars are also very touchy regarding wheel balance and alignment and have driven some members insane chasing that last bit of vibration.

 

We will have owned my wife's 2006 XK8 for one year tomorrow. It has 245/40/19 Yokohama YK580 all-season tires up front (installed October 2012) and 255/40/19 Yokohama YK580 all-season tires in the rear (installed April 2012)....

What I've learned is that when I ran the tires at my preferred 33 to 34 psi in an effort to maximize the treadwear, it actually increased the treadwear down the center of both rear tires. So I lowered the pressure to 31 to 32 psi. I watched the tires for a couple of months and felt that rear center wear was better but still present. So I lowered the pressure again to 29 to 30 psi, and the rear center wear now appears to be normal....

What remains to be seen is if these lower-than-initially-desired pressures will still lessen the lifespan of the tires even though the rear tires now appear to be wearing evenly across the tread....

 

In the Vehicle Care section of the manual for 18" it recommends Maximum Comfort speeds up to 100 mph 26 psi front and 28 psi rear. Normal pressures front 32 and rear 34. I like 28 in the front and 30 in the rear, the older girls just seams to handle better. With the crazy temp. swings we have been having 78 degrees one day and 30 degree the next i have seen 4-6 psi +/- changes in the pressure. All my rims are 9 x 18 so I can rotate the tires to get max. life. Plus the handling seem much better on those mountain roads. Jim

 

My question is about the nitrogen filled tires. The local costco where i got my new tires last year fills them with that(32 all). Is it ok to top them off with air? They're reading 28 all lately and I'm noticing inner/outer wear on all of them and want to get them back up to 32.

 

Nitrogen has a lower thermal expansion than air so you see less pressure variation as temperature changes. Adding air will dilute that effect but won't cause any other harm.

I know it is technically beneficial but I've always wondered how much practical benefit you really get from nitrogen.