When purchasing my '03 XK8 I noticed I have two different brands of tire on the back wheels, one a Pirelli P-zero, the other an unknown brand (to me). Both tires are about 60% worn and are the same size. Can this cause any problems? Just some guidance requested.
Thanks,
Bart

 

Your question would get the proper exposure if it were posted under the right forum. This is for introductions to the forum.

 

... this is one of my first times joining any forum. I am trying, but it is a bit confusing.
Thanks for the tip, though - I'll keep poking around.
Bart

 

Bart,
Not a problem. I will move it over to the XK8 section for you.

 

I don't think it would cause any problems unless one tire was a radial and the other was a bias-ply. That's unlikely because I haven't seen bias-ply tires available for a decade or more. They are pretty unusual these days.

You might want to check your rims, however. The rear rims are supposed to be wider than the front rims, and sometimes tire shops accidentally put both rear rims on one side and both front rims on the other.

 

Also... just check the tires to make sure they are both the same size.

 

"Flydutch" you won't get any problems with diffrent Brand tires, you may feel a differents in ride, only cause tires feel a little different from each other.Other than that, should be OK, as long as they are the same SIZE.

 

Bart,

IMO, depending on how aggressively you plan to drive, there could be a concern here.

When turning, the rear tire on the outside of the turn is doing most of the work of keeping the rear end of the car from getting loose. The P-zero is a very sticky tire and will create a certain feel when it is the outside tire. If the rear tire on the other side is much less sticky -- and many are -- you'll have a whole different situation when turning in the other direction. That could create an unpleasant surprise. (These are fairly aggressive turns we're talking about. If you won't be making any of those, not a problem.)

You didn't mention the front tires. As a general proposition you don't want stickier tires up front than on the rear. If you have P-zeros up front, the brand-X on the rear could be a troublemaker for this reason as well.

 

I always thought it best to use the same tire on an axle. Different on front and rear is not as big a deal. I have a sticky rear tire and a harder front tire, although they are both summer only to have the same basic performance characteristics.

 

My OPINION is that if you're not going to be racing the car on the track or running from the police, the mismatched tires are fine. But that's just my opinion. I'm cheap and I'd drive those tires until I needed new ones, then I'd get matching tires.

 

Appreciate your input... I don't plan to race around too much - car is to new to me and am still getting my Jaglegs. The three oddbrand tires on the car (can't even remember the name, and I am away from home so I can't go out and look) seem fine but they are very noisy (very agressive tread pattern).
Since our XK8's are the same model year, I'm keeping my eye on you! Your power headrest repair video was great! Mine are both dead, so, after more study I will do the repair also.
Can't wait to get full access to the forum!

 

In thinking about this a little more, I'd go further than what I said earlier. Unless the brand-x has a traction rating similar to the P-zero, I'd replace it.

Even if you plan to drive very conservatively, if you someday have to execute a violent swerve at highway speeds, the last thing you want is a mismatch, especially on the rears.

Tires matter. At times, some of which we can't predict, they matter a lot.

 

Dennis-
You have a good point - it occurred to me also; am shopping for tires.

 

WAIT! PM me before you do the repair. I have some really awesome heat shrink tubing that I'll send you. I bought it to do my car, and I have way more than I need. My driver's side headrest quit working for the third time. The heat shrink that you can buy at Radio Shack or Home Depot just isn't strong enough. I bought some thick-walled, adhesive lined heat shrink tubing that is incredible. Once it shrinks it is very thick, tough, and rigid. I've been using it on the ends of the wire for the convertible resistor, so the people who bought those can vouch for the sturdiness of that heat shrink tubing. I feel certain that if I do the repair one more time using TWO layers of this heat shrink it should last forever.

 

And in regards to the tires, my OPINION is that the anti-lock brakes will compensate for any difference in traction from one tire to another. So the worst case scenario would be that the "sticky" tire would start to lock up and then the ABS would kick in, essentially making the traction of that tire equal to the traction of the less sticky tire.

For liability reasons most big name tire stores will not put a tire on a rim if the tire won't properly fit the rim or if the load rating of the tire doesn't match the car. They don't have a problem mismatching tires, however.

On the other hand, this is a good excuse to go buy some new tires with a cool tread pattern!

 

The ABS can help with in-line forces (faster / slower), but not lateral forces, so it can't equalize the stickiness of tires with respect to turning.

This is of course just opinion too. But tires are an area I take very seriously, so I would want to err on the side of caution. YMMV.

 

It's not just ABS, there's also traction control. It will selectively brake any wheel it deems necessary and cut power to keep you from losing traction. I would assume that ABS is still functional if you disable traction control. I usually disable it... I'm not sure how well it works and being an old school driver, I don't trust it.

 

Same story here. ABS and Trac can modulate braking and/or reduce throttle if they sense something funny about the rates of rotation of different wheels. This can help us out of trouble if wheel(s) are locking up, or one driven wheel is spinning.

But neither ABS nor Trac can detect or help with sideways slide of a tire ... something that always happens to some extent, and can get out of hand, in a turn or a swerve.

So my own preference would be not to have tires left and right with dissimilar traction characteristics. Just my opinion. One of those things that probably will never matter (sort of like an air bag maybe) but then again it just might.

 

Agreed. Look at the info posted at the Tire Rack website. Sometimes the same size tire has different revs per mile, tread pattern, etc. from different manufacturers. Both tires being the same size may not mean much.

I'd go to Tire Rack website and check the specs for Both tires. If they're not the same specs, I'd replace one to match the other. Just my 2 cents, but jaguars are NOT cars to cheap out on (unless you want to risk Very expensive repairs down the road) or don't drive them much.

 

Probably the best idea.

Lumpy tires won't let you enjoy your new ride as much as a new set all around.

As an aside on the current situation, if the *rolling* radius is different on the two sides, a differential works harder all the time. It's like being in a wide turn all the time.