New Tire - Must Be On Rear?

Well if it's a front drive car it is best to have the tires matched in size and wear. Keeps you from having problems with uneven wear due to the different tire sizes. Many companies have CYA rules in place to prevent lawsuits for some strange stuff! Wal~Mart for instance has a store policy that they will not install a tire on your vehicle that does not match the door sticker. Why? Because they were sued by a person with a lifted P/U who had them put on bigger rubber. The ABS failed to operate properly and it was determined that this was due to the over-sized tires and vehicle speed. Lawsuit was settled out of court and company policy was changed. (some of the T&Ls no longer even carry tire sizes that are not factory sizes)

I had the same BS from them except I'm sure they told me they had to put the new tires on the front. It's not a law, it's just some policy written by their lawyers.

IMO that is BS. I bought 2 tires at Goodyear a few months ago and they also wanted to put them on the rear. I told them I wanted them on the front to which they had no problem doing. They made no mention of "having" to put them on the rear.

Now that I re read your message they probably wanted to match a used tire with your other one (assuming it's the same brand) but it's probably no requirement. What if you get a flat down the road? Assuming your spare is a full size tire are you going to be required to change two tires putting that new spare on the rear, and moving the rear tire up to the front?? I don't think so. :)

It's not a legal requirement (that I'm aware of) but it is good practice. Probably a company best practice. The reason is that if a tire loses traction you want it to be the front, because the coefficient of sliding friction is less than that of rolling friction, so the vehicle will tend to keep pointed in whatever direction it was traveling before the front washed out. If a rear tire loses traction esp. while braking you're essentially trying to balance a pencil on your palm - not impossible but not easy, either, as the fronts are trying to stop but the rears aren't, at least not as hard, so the rear end of the car will try to come around on you.

nate

Where was this? That doesn't even make sense.

nate

Asht> I had the same BS from them except I'm sure they told me they had to

The idea is that the average driver can handle an understeering car more easily than an oversteering one. If you've driven the original VW Beetle for very long, it would be no problem.

If this is a front-wheel drive car, you want to do this so that the two driven wheels are the same diameter.

If you had a rear-wheel drive car, you probably want to put the new tire on the front.

--scott

I don't think there is a "law." I think this is a cover your rear end practice and is a rule at the big box retailers like Costco. The theory is simple - if one end of your car is going to loose traction first, it is better if it is the front end. It the front end breaks loose first, the the car usually continues in a straight line. This may end up with you in a ditch, or in the raer of the car in front, but in many cases that is the lesser of two evils. If the rear end breaks loose first, the car will spin, and unless the driver is very competent, it is possibe that the car will end up going sideways and rolling, or spin into the opposing lane of traffic or something else nasty. These are worse options - usually. Car manufacturers have been designing passenger cars so that the front end breaks loose first for many years (understeer). Putting the better tires on the front can counteract this design "feature" by improving the front end traction relative to the rear end traction.

In the case quoted, this seems to be a trivial worry. The guy was getting exactly the same tire, with just a little less tread than the tires already on the car. I assume he is roatating them. I would just switch the rear tires to the front in a normal rotation pattern. The front and rear tires wear differentially (as do the side to side tires).

Ed

Tread wear has almost no effect on rolling diameter. I know this seems counter intuitive, but a friend explained this to me years ago. I've checked and confirmed this over the years.

I'd be more worried about batch to batch variation in rolling diameter becasue of internal structure changes than in differences in rolling diameter becasue of tread wear.

Ed

"Nate Nagel" wrote

I'm the OP, and the Costco was located in Torrance, California, a suburb of Los Angeles.

It was put to me you put the best tires on the rear, because you can't steer the rear wheels.

This question is similar to asking, where should I part my hair? You'll get a different answer from everyone.

Never heard of any law as to where to put tires, however.

I doubt it's a law. I doubt it's even a regulation. As others have already mentioned the tire companies recommend new tire go on the rear of front wheel drive cars. I thought otherwise but here's what the printed word says, seems to be serious enough to justify putting the new ones on the rear, I suppose, I don't know how you are ever going to get the rear ones to wear down enough to rotate them to the front though.... anyway here it is,

Tires as in plural? This makes sense to me. On the other hand, if its only one tire, I'd rotate BOTH rear tires to the front and put the new one in back.

Phoenix. My memory is a little fuzzy but it seems to me that at one time the big deal was that "new tires need to go on the front so you can steer". But a few months before that it was "tires need to go on the rear so you don't spin". It's all driven by lawyers and lawsuits. Now the chains won't install "old" tires. I had a pair of brand new (as in unused) Michelins that used to be spare tires and Discount Tire wouldn't install them. I had to take them to a gas station/auto repair place to get them mounted.

I bought 2 new tires at Firestone (in Pennsylvania) a couple of years ago, and they said that their policy is to put new ones on the rear. I requested otherwise, and they did it after I signed a waiver on their service order. So, I'd say it's a company policy rather than law.

That's the venerable conventional wisdom passed down to me by Dad, but it's apparently been contradicted by new research. (I might add that if you're worried about "blowouts," which are not as common as they used to be, you need a new tire no matter what its position, though even a regular sort of flat at speed is not necessarily great fun.)

Costcos of my acquaintance have had this policy for several years. Their actual policy is, "When you select a pair of replacement tires in the same size and construction as those on the car, you must put them on the rear axle. A single new tire must be paired on the rear axle with the tire having the most tread depth of the other three."

I think it's company policy, in accordance with recommendations from the Tire Industry Association

rather than law or regulation, but it's fairly common now. See for instance or in greater depth How they handle cars and light trucks that intentionally have different tire sizes and/or types on front and rear, I don't know.

Cheers,

--Joe

Its not required by law, its required by their lawYERs. There's a misguided belief that putting "less grippy" tires on the rear of a car will cause it to be more likely to spin out of control (ie, oversteer or be "loose.") Understeer is generally safer than oversteer, so they don't want ANY liability that they might have been responsible for causing the car to oversteer.

The fact of the matter is that the vast majority of passenger cars, ESPECIALLY front-drive cars, are built with such a huge built-in understeer that you'd have to put *really* slippery tires on the back to make them oversteer. IMO, putting the worn tires on the back of most FWD cars will actually give them something a little closer to a neutral handling characteristic.