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For many years, tire installers have wanted to put the better tires on the front, no matter what the vehicle. So, if you went to buy two tires instead of four, or even just to have the tires rotated, the new or better tires would normally be put on the front. However, we're pretty sure that all tire manufacturers are now recommending having the better tires on the rear. Not only will some retailers refuse to put new tires on the front when buying only two, we've even heard that putting new tires only in the front is illegal in some states (though we were unable to verify the latter). Why is this?
The Short Answer
Continental tire was kind enough to send the boss (along with many others) to their proving grounds in Uvalde, Texas, and they did a demonstration of this. It involved each participant driving around a circle at 50 mph. At the end of the circle, they had about 1/4" of water for about 20 feet. Each person drove two matching cars: one car had tires with more tread on the front, and the other car had tires with more tread on the back. When they hit the water in the car with the better tires on the back, the front tires lost grip, the car wouldn't continue to turn and the car skidded straight ahead. On the other hand, when the participants hit the water in the car with the better tires on the front, the rear tires lost grip first, the rear end of the car started to come around, and some people even spun! This type of situation can certainly happen in mountain driving, but the same thing can happen if you have to slam on the brakes or swerve.
Therefore, there are two reasons why you would want the better tires on the rear. The obvious one is that many drivers are not used to controlling the car when the rear end comes around. The other is that the majority of the safety equipment in most cars is designed for front impacts, and usually very little protects you from side or rear impacts. Therefore, for maximum safety, the better tires should be kept on the rear.
You may argue that you drive slowly, and therefore never get into this type of situation. Never? Really? What if someone pulls out in front of you? Anyway, think about it.
The problem with this is that since most cars wear their front tires faster, you will never be able to rotate them properly, will never get the best wear out of you tires, and if you have a mileage warranty, it will be voided because you haven't rotated your tires. (As a side note, the requirements for mileage warranties are not too easy to meet, so trying to do so may not even be worthwhile, (see our "Mileage Warranties" page.))
To elaborate: The old school of thought, (which we subscribed to before Continental's demostration) was that as your tires wear, the front tires normally wear faster. Also, front tires tend to wear more on the edges, and rear tires more in the middle. Since these things are true, not only would wear be distibuted more evenly on all four tires, but all four tires would wear more evenly across the tread face, and therefore wear longer. This is why all manufacturers require regular rotations for any mileage warranty.
So, if in the interest of safety, you decide to keep the better tires on the back, you will probaly only rotate them if you're buying two tires. Since most vehicles wear their front tires faster, within a few thousand miles, the front tires will be more worn than the backs so you won't want to rotate them then. Then, since the front tires can wear out much faster than the rears, you will want to probably want to replace only the fronts, and then move the rear tires to the front. Sadly, you can't have it both ways, unless your vehicle is one of the "exceptions", you have to choose either wear (economy), or safety. At Souza's, we still leave this decision to the customer, but we're leaning more and more toward safety.
You may have noticed we keep saying "normally" and "most cars", and that is because there are exceptions to the rule. Rear engine vehicles, diesel trucks, and sports cars with limited slip differentials will usually wear their rear tires faster. Actually, most diesel trucks have "LSDs" and that may be why they do this. At any rate, if your vehicle wears it's rear tires faster, you should definitely keep them rotated. If the rears wear faster, then to keep it safe, you'll want to rotate the tires, and then you'll get better wear too! The only problem with this is that most of these vehicles are pretty hard on their tires, so even though they may not get good wear anyway, on the "exceptions" you can optimize both wear and safety by consistent rotaions!
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