rensho said:
The new tires are better off on the back though. For a car going forward in motion, you want the most drag/friction in the back to keep it pointed in the 'right' direction. Similar to how a rudder on a boat, parachute on a cargo, tail on a dart works. Once the car starts sliding, and the rear starts to come around, assuming all four tires are sliding, if the fronts have more drag/grip, the rears will then come past the fronts in the direction of momentum.
Actually, if I were to put two new tires on a car, they would go on the drive axle. On a front wheel drive car, I'd put the tires on the front. If it was a rear wheel drive car, I'd put them on the back. The reason being, and this is VERY obvious on our Integra GS-R with the Falken Azenis Sports on it (these tires only last about 20-25k miles at MOST), after 12k miles I had neglected to rotate the tires, as it's the wife's daily driver and I didn't really think about it during the one or two oil changes a year I do on that car... After 12k or so, the fronts were SIGNIFICANTLY more worn than the rears due to the fact that they are constantly having to put down power to the ground, turn, AND brake all the time. After rotating them, the 'good' tires were now on the front and it had no negative effect on the handling of the car having better tires on the back.
In this situation, if I had not rotated them and my fronts were to have worn out significantly before the rears, I would have needed a new pair of tires. To achieve equal wear, assuming I was still lazy and would never rotate them again, I would put the new tires on the front, at which point the rears would probably wear out around the same timeframe as the brand new tires added to the front of the car.
If I did it the other way around and put new tires on the rear, and put the older tires on the front, I'd need two more tires again much sooner, instead of hopefully them all wearing out around the same time the next time around.
Also, to those that say new tires have to go on the rear, what happens when you have a vehicle with a staggered tire setup? My Honda S2000 has wider tires in the back. The rear tires last 8-10k miles. The front last 12-15k miles. When I put a new set of tires on at 10k miles, okay... That follows your theory... Then 5k miles later, when my rears are half worn already, I have to put a new set of front tires on the car. Are you going to say that this is unsafe? Think about it... Not every car on the road has the same size tires front to back. Some Porsches, some BMW's, 350Z's (I think), etc... Lots of cars have staggered setups that would not allow you to put new tires on the rear if the fronts needed replacing at a different time than the rears.
Just something to think about. It's not a cut-and-dried answer as to where to put the tires. It has a lot to do with the car and other factors.