2006 XK8 with 255/40/19 rears and 245/40/19 fronts....

My owners manual specifies 34 psi for the rear tires. I installed a pair of Yokohama YK580 rear tires back in mid-April, they currently have 11,300 miles on them, and I've kept them consistently at 33 to 34 psi. I check the pressures every weekend. The car's alignment was checked in early October and found to be well within Jaguar specs so no new alignment was necessary....

For the first time in a couple of months I checked the treadwear yesterday. Both rear tires read exactly the same: the centers are down to 7/32 while the inner and outer edges are not quite 9/32. When new, the tires started at 10/32....

The front Yokohama YK580 tires are wearing evenly at 33 psi. No issues with them....

Regardless of what the owners manual says, 33 to 34 psi is too much pressure to allow for even treadwear across the rear tires. I backed them down to 31 psi. Don't want to go any lower until I see if more even treadwear results at 31 psi....

What pressures are you guys running in your rear tires in an effort to get more even treadwear? Is this strictly a 19-inch wheel issue, or do you 17-inch wheel owners have to deal with this as well?

 

I run 18inch with 31psi front and rear no probs on motoways or round town good grip and nice smooth ride .

 

Jon raises an interesting point. I have read that some premium tires have a variable rubber compound across the face of the tread. That being said, perhaps it follows that the tread ware will follow the softest compound formula across the tire.

Whatever the case, it sounds like we should be carefully monitoring the tread ware on our tires a lot more carefully than we did in days of yore. Perhaps more often too. SOAB

 

Yes indeed, these Yokohamas have wet zone tread blocks, dry zone tread blocks, and maybe even Twilight Zone tread blocks. To hell with the tread blocks - I just want even treadwear across the rear tires. Perhaps 31 psi or maybe even 30 psi is the answer....

 

The wider the tire the more likely it will succumb to center wear. The further the center of the tire is away from the control of the shoulders will allow overinflation and centrifugal force to have their ways with your treadlife. The use of certain synthetics (mostly nylon is used as a control fabric) will help control tire growth as it heats up. Think of a stray thread on a nylon windbreaker. If you aplly heat from a match or lighter the thread will shrivel. This is the reason those synthetics are employed. As the tire heats the fabrics will shrink and help 'pull in' the center of the tire. The downside is the flat-spotting that occurs when a warm tire is parked on a cool surface.

OEM recommendations for tire inflation pressure is a huge compromise between safety (1st - not allowing the pressure to be so low as to cause a blowout), CAFE (2nd - have to keep the corporate average fuel economy high to avoid gas guzzler taxes), handling (3rd - to keep the car rags from stating the car drives like crap) and, last because they don't really care about your money/tire life.

Then there comes the tire manufacturers trying to be all things to all people. They try to make a sticky tire that is quiet, has good handling, reasonable tire life and foremost, profitable. And they have to make it work on all kinds of cars, not just your particuar model. Well, there are tires that are made to Porsche spec, some made to TPC (GM) spec, etc. but you get the gist of what I'm stating.

Have you ever read through Tire Rack's customer reviews and noticed how some tires get really crummy reports from drivers of particular cars? I can think of several tires being burned on the cross by some VW (Jetta & Golf in particular) owners and others by pentastar owners. Some tires just don't work at all on some models.

I've enough history with many makes of tires, some so much so that I would never consider buying or recommeding them, at least not without caveats. Keeping that in mind, when I say I'd never own Yokos it's based on my personal experience that no matter how sticky they may be they weigh too much and are too harsh for everday usage. They will develop noises and lumpiness before they are half worn. I've seen it too many times to take a risk with my money. But I'm not everybody and don't expect any/all to agree with me. However, 34 psi is way too much for a Yoko, in my book. Personally, I'd begin around 26 and drive it in various conditions to judge its performance and safety then watch the tread wear.

 

Brutal informed me many years ago, that the 34 is a guideline, and he often drops to 32 psi for owners and doesn't even tell them. My fronts are at 32 psi, my rears however, I found that 34 was bad for center tread wear, 32 was better, and I've worked my way down and settled on 29.5 psi and I am getting good, even wear across the tires now. No change in ride or handling.

 

Watch the tread wear on the inside of the tire especially on the front tires. I just had my fronts flipped. I wish I had done it a little sooner. The rears are wearing evenly so far. On todays cars they are set up with the a slight cant inward at the top. Discount Tire says that just about all newer cars are set up this way. I know my XJ6 wears more on the inside on both front and rear. I was too late checking my fronts on that car and lost two tires that otherwise would have gone another 10K easily. I have checked the alignment twice with that car and found it well within spec.

Watch the inside tire wear on all Jags and be prepared to flip the tires as needed.

 

On the other hand, there are some people who love Yokohamas and have had them on multiple cars in succession. These people find them to be quiet, stable and forgiving. The touring tires are as good as the Michelin touring tires.

The poor man's tire pyrometer substitute is ordinary white blackboard chalk. Once the tires are warmed up, draw three or four heavy lines across the tread of the tire and partially up the sidewall. Drive the car and look at the lines. You want even wear across the chalk when the tires are driven in your normal style. You do not want to see the chalk disappear from the sidewall as that would mean that you are rolling over onto the sidewalls during cornering.

How many of the people complaining are running staggered rim sizes? The tire sizes are staggered in at least one post.

Logic dictates that staggered rim and tire widths may require different inflation pressures between front and back.

Even more so if only the tires differ in width while mounted on the same width rim.

The tire pressure has to bring the normally concave face of the tread out to just the right profile to wear evenly. This may not be completely flat as the wear encountered while running straight must be balanced by the wear while cornering. An enthusiastic or unskilled driver can wear the shoulders more than another driver. So they would require a bit more pressure to balance the wear. That is handy because more pressure is better for sidewall stiffness in any case.


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The Twilight Zone!

Your wear pattern is a classic for over inflation.

I was running 32 Front (245/45 ZR18) and 32 Rear (255/45 ZR18) on my 2001 for normal, unloaded use. Increased this to 34 Rear when loaded with luggage for touring. No abnormal wear either front or rear over 24k miles.

I'm now running the same pressures 32 Front (255/35 ZR20) and 32 Rear (285/30 ZR20) on my 2005 for normal, unloaded use and again only increase this to 34 Rear when loaded. Haven't covered sufficient miles yet to make a true comparative assessment but, as yet there's no abnormal wear and I'm not anticipating any.

Jaguar recommendation for both vehicles is 32 Front and 34 Rear but this is a compromise for average use. The handbook also states to increase pressures by 2 all round if using non approved tyres which is strange advice.

I believe the recommended 34 Rear is too high on a vehicle which will almost never have rear seat passengers or be carrying any significant weight in the luggage compartment.

Graham

 

Agreed. The usual use for our cars is with one or two occupants and no luggage.

I run 30lbs all around and even this provides a "Firm" Ride.

 

Appreciate all the comments....

I'm well aware of staggered tires sometimes requiring different pressures on different axles. That's yet another reason I've never liked staggered tires (the main reason is their limited rotation pattern). But that's what our XK8 has, so I'll deal with it....

As previously mentioned, I've backed the pressures down to 31 psi all the way around. I'll watch them for the next 1,000 to 2,000 miles, then adjust accordingly. Our temperatures continue to drop as autumn rolls on, so Mother Nature will contribute to the equation as well. 30 psi in the rear may indeed wind up being the optimum target....

But just give me a good ol' 16-inch 75-series H-rated tire and I'll get 60,000 miles out of it without a whimper....

 

Plum,

That business about the chalk across the tread is brilliant. In 50+ years of driving over 2 centuries I never read or heard about it.

KBO mate

 

Graham

Take it that is 285/30 20 rear?!

The Jaguar recommended pressure for 20" wheels with 255 front/285 rear is 32psi front and 30psi rear at all times!!

Attached XK pressure chart

 

Beav brings up the best info. And it does depend on the tire brand and model. The worst imo for center wear are the michelin pilot sport AS rain tires. These will flat wear the centers to cords leaving 5-6 32nds tread remaining inside and out and not from overinflation. Just contruction of side walls and material. Ever watch a top fuel dragster with soft sidewalls running 6 psi. The tires are18" wide 32" tall till they hit the gas. Then they grow big and tall. The contact patch narrows to half the resting width and the contact patch lengthens. Yes this is over exaggeration but it does show what the centrigual force does to a tire. Maybe your yokos are similar jon. I dont know i dont have experiance with them consistantly like mich's. To me the micheline are terrible in this regards, maybe yours can be changed by lower pressures, maybe not. Sucks to gain this kind of experiance at the costs of tire today.
Ezdriver. Your tires were telling you thyey didnt like the amount of toe in. You had too much toe out, i dont care what the alignment machine said. I always say green doesn not equal even tire wear on specs range and you dont drive to work on the alignment machine either. Just had this same discussion friday with a land rover tech on wear and everyone standing around the alignment machine wondering why the tires are wearing inside but the alignment was green in spec(but away from the mid range to the outside) i got underneath and pushed out on the inside of the tires and it swung way out into the red
and replied. "he doesnt drive to work stationary on this machine, he drives down the road that pushes out on the tires and it does that(goes into the red) while he's driving", look at the tires not just the machine. class over

 

Yes, it had a certain back to basics logical appeal when I first heard about it. Just as good as melting beeswax on a heated nut to break it loose. This stuff is going to be gone forever some day soon.

Ever tried hunting down blackboard chalk lately?

 

Just to get everyone on the same page, remember that most tires read 2 to 4 psi higher after being driven at highway speeds for just five miles or so. So with my current XK8 pressures set at 31 psi cold, these tires will read 33 psi to 34 psi once they've been on the road for a few minutes....

 

All the Chinese outlet stores here in the US still sell chalk(aka Walmarts) so do the office supply stores in the school sections. chalk and shoe polish has been used in racing circles for yrs. I still use on the race car slicks and wheely bar wheels to monitor tire to wheel spin, proper loading of suspension on launch, contact patch for proper tire pressures etc..

 

I envisioned this and thought to myself, I wonder if he used a laser pointer or an old-school stick when directing the attention of the young techs to the alignment monitor.

 

no, i try to be somewhat diplomatic as ive been told by women and my kids im critical. Ive never ment or taken it that way but i look at everything on can it be improved, done better. But then i guess i didnt earn my nickname by being passive. Heres my new plate for the truck i cant wait to get back on the road with the newly rebuilt engine and bigger blower

 

Brutal, I'm feeling ya Bud. Peeps ask questions then try to argue your answers. Makes you feel they were seeking validation rather than an honest answer. So we end up being tagged as critical, etc.

Also agreed on alignment specs. So many times OEs print whack specs in order to compensate for design shortcomings. The proof is in the pudding when your $200/ea. tires are shot. Then again, I've seen a lot of guys not even consider a little play in the wheel bearings as a concern when setting toe... they just 'hit the green' and go.