Is it just BMW that does not recommend tire rotation?

The *wheels* didn't last that long on the first Minis running crossplies. Seems the designers thought the buyers of this tiny car would slow down for corners. Of course they might have if the brakes worked. ;-)

Just because the tire is disigned for one direction of rotation doesn't mean it can't be used on right or left. For that to be the case the tire would also have to be asimetrical, inside and outside tread or internal construction would be different. I have used tires (these were autocross tires) that were asimetrical and directional and these are usually stamped with a left or right only designation, and if the front and rear were not the same size then they could not be rotated. If the tire is just directional and the front and rear were different you could rotate left to right but you would have to dismount and remount the tires inside out on the rim.

Can you point me to the BMW site the recommends no tire rotation?

packages)

Marcio is correct. Floyd has uncharacteristically used an imprecise term here (unidirectional) and used it somewhat incorrectly. Here's how they work:

1) A *unidirectional* tire definitely *can* be used on either side of the car so long as it's symmetrical. Once mounted, though, it should stay on that side of the car unless turned around on the wheel. 2) An *asymmetrical* tire can be used on either side so long as it's not unidirectional. These may theoretically be swapped side-for-side without dismounting. 3) An *asymmetrical unidirectional* tire can only be used on one side of the car and shouldn't be swapped side for side under any circumstances.

As long as all four tires are the same size, #1 and #2 require four identical tires. #3 would require two pairs (one pair/side) of different tires per car.

For staggered tire sizes, #1 and #2 would require two pairs (one pair/axle) and #3 would require four different tires (one/corner).

Got it?

-- C.R. Krieger (Been there; done that)

No, but when you have different size front and rear tires in combination with unidiriectional tires, then a MOUNTED tire/wheel combo is unique to each corner of the car. You COULD dismount the front tires and swap them side to side and re-mount them, but SHEESH! Why bother?

It all depends on what you're trying to maximize.

If you're trying to extract the utomost performance from every tire, then don't rotate because once a wear pattern is established, switching it to a different corner of the car would result in a sub-optimal contact patch.

On the other hand, if you don't expect to push your car to its absolute lateral G limit all the time (as in the case of 99.9% of daily driven cars!) then rotating the tires and tolerating a slightly sub-optimum contact patch right after rotation WILL get longer service life out of each tire.

The vast majority of cars on the road- ESPECIALLY front-drive vehicles- benefit a lot from tire rotation in the long run.

Yeah, you're right, I mis-used the terms asymmetrical and unidirectional. I plead two things:

1) we're talking "tire rotation" here. IMHO, no unidirectional tire should be rotated left-right/right-left - especially on a BMW. In any case, that would require a re-mount. 2) someone specifically mentioned the NSX, which I had experience with as an owner of a '93. If you go to tirerack, you will discover that the OEM tires (the Bridgestone RE010 is no longer available) were uni-asy and different size f/r: the Yoko A022H1 is in this category.

Floyd

imprecise

unidirectional.

If you've got enough negative camber goin' along with a cheap tire mounter on hand, it could be an economical move. OTOH, the majority of unidirectional tires are only unidirectional for reasons of water dispersion. According to the tire engineers I've queried about this, as long as there's no water involved, it really doesn't matter which direction they run, so side-to-side swaps are certainly a viable alternative if you really need to drive the car instead of worry about whether the tires are 'proper' or not.

And you're back in form, as ruthlessly correct as ever! Remarkably, the old A008s were also front-rear different, even in the same size. These were marked for rotational directions for FWD and RWD cars as well as being notoriously asymmetrical (slicks on the outer half!). Tire Rack would ship two pairs and the pair on the 'non-driving' end would appear to be turning backwards, according to the arrows on the sidewall. Fortunately, I never had to figure out what to do with these on an AWD car. =;^)

-- C.R. Krieger (Been there; done that)

Says so in my driver's handbook.

"C.R. Krieger" wrote

I just wish my brain and fingers would always get together - of course sometimes my brain just goes sideways while my fingers are typing forwards...

Floyd

I can really see this if you've been on a track going left, then next weekend on a track going right... ;-)

Floyd

There are all sorts of wacky configurations. My current Pirelli PZero Nero M+S tires are non-directional asymmetric. Some tires are directional asymmetric. The wackiest of all are directional asymmetric left/right specific.

Yep. Like the NSX. A different tire on each corner. It's not that bad once you get used to the idea.

[...]

My ALPINA B10 V8 has 4 different tyres - each has a direction of rotation and an outer edge, rears wider than fronts.

I'd still not rotate tyres, even if approved - false economy IMO.

A

Well, sort of... I've said this before, but I'll say it once more; Rotating tires is is not, not has it ever been, about increasing the total mileage of a tire, *except* when considered as a set.

By rotating tires one can even out the wear at the 4 corners and thereby equalize the wear so that the set of 4 all wear-out at the same time.

Or to state it another way, it will not extend the life of any single tire, but rather will allow the 4 to be spent at the same time and be replaced as a set.

The value in that is especially evident when considering how often a particular tire model is obsoleted and replaced with a new one in any particular brand.

Some folks advocate replacement of the spare tire after a certain amount of age regardless of how much wear it has attained, for safety reasons. Obviously, any scheme that allows the spare into the rotation will extend the life of the "set" by ~20%.

OTOH, if you have a brand/model of tire that is readily available over a long time period (or if you wear them out quickly due to high annual mileage) just replacing the axle that wear quickest would be equally as economical as replacing the set.

-Fred W

-Fred W

Correct. There are unidirectional tires. They can be used on either side. But there also are asymmetrical tires that can be only used on one side. If a car is fitted with asymmetric tires that are also staggered (wider in the rear) there is zero opportunity for tire rotation.

-Fred W

I don't uderstand the theory of this statement. If you are running a tire which has worn a particular way, and now has a sub-optimal contact, wouldn't you think that the "high spots" (the areas with greater pressure in the new location) would wear faster and therfore negate the total tire life assertion?

-Fred W

Yes, but the tire thus lasts longer than it would if you left it where it was so that it wore through to the cord in the first high-wear area.

Frankly, most cars don't wear tires that badly except some FWD vehicles. Its entirely possible to wear two sets of front tires on an FWD down to the wear indicators without showing significant overall wear on a single set of rear tires. But by that time the rear tires are so aged that they don't have the grip they should and are subject to tread separation and other problems. It seems to me, based on several experiences now, that modern tire designs are more sensitive to the aging of the rubber compounds than the tires of the 70s. Even if you had a set of tires stored in a dark, dry garage for 6 years, the odds of them lasting a full lifetime when you put them on the car will be VERY small- they'll probably develop cracks or separations long before they wear out.

It's highly optimized for handling purposes, and if you think about it, the front tires are doing different work than the rears, so it makes sense from a performance point of view. The outside of the tire also does different work than the inside...

But yeah, it can kinda suck if you get a nail in one tire and they happen to be back ordered on the left front tire for two weeks... and your only spare is the donut... especially because cars like Vettes look absolutely silly on the spare. Imagine a Viper with two donuts on the back.... now imagine trying to drive it. :)