QUOTE (tomsoni62 @ Apr 18 2009, 06:48 AM)
I just got a used 2004 6s and there's a mix of Yokes and Michelins on the car. In looking at the repair records, it looks like the tires were replaced at least twice, and there's 79k miles on the car. Never having owned a Mazda, and at least 30 years removed from driving a fwd car, it sounds like the 6 either chews up tires, or the previous owner was doing something wrong. Any thoughts/suggestions?[/b]
Any FWD car will cause wear of the front tires at least twice as fast as it causes wear on the rears. Some Mazda6's have caster/camber/toe-in such that the outside edges of the front tires wear out even faster; some don't; but if you do not rotate your tires frequently, your fronts will wear much faster than your rears.
There are two schools of thought about how to live within those parameters. One school says that you rotate your tires frequently to keep the wear even. The other school says just let your fronts wear down to the indicator bars, then move the rear tires to the front and put a pair of new tires on the rear. (There is a third school that says always put new tires in front; that school is wrong, but it gets repeated a lot, anyway.) I subscribe to the wear-out-front, replace-rears school.
For safety, you always want to have the pair of tires at the rear to have: (a) the better dry grip -- usually inversely proportional to the Treadwear number on the sidewall, and (b) the deeper grooves/channels for water evacuation. This can cause a dilemma when the less-worn tires (deeper grooves) have the higher Treadwear rating (less grip). In that case, I usually recommend putting the tires with the better dry grip at the rear, on the theory that in most cases, the front tires will have "wiped" the pavement mostly dry fractions of a second before the rear tires reach the same spot of pavement.
The reason you want more grip at the rear is the same reason that most bicycles are set up so that the right -- in most people the stronger hand -- handbrake stops the rear wheel and the left (weaker) handbrake stops the front wheel. If you grip hard on only the front wheel brake of a bicycle, the front digs in and the rear is likely to rotate right over the top and throw the rider. If the front wheels of a car dig in while the rear wheels lack sufficient traction to bite, the rear end of the car is likely to come around in front of the stationary front wheels.
The final consideration in this calculation is mixing all-season and non-all-season tires. Generally, all-season tires have 20 to 40 percent less
friction (stopping power) on wet pavement than non-all-season tires do, due to the chemical alterations to the tread compound of all-season tires to lessen their tendency to shed water: that means that they ride on a film of water whenever the pavement is wet. You need to take that into account, then, in deciding which tires to put at the front and which to put at the rear.