Dear Auto Advisor,
My best friend says that the 2 new tires I bought last week should be on the front of the vehicle, not the back. Please let me know were to find this information and where should the my new tires go? He says it is just common sense to put the new tires on the front of a car.
Common sense suggests that since the front tires wore out first and because there is still about half of the tread remaining on the rear tires, the new tires should be installed on the front axle. This will provide more wet and wintry traction; and by the time the front tires have worn out for the second time, the rear tires will be worn out, too. However in this case, common sense isn't right...and following it can be downright dangerous.
When tires are replaced in pairs in situations like these, the new tires should always be installed on the rear axle and the partially worn tires moved to the front. The reason is because new tires on the rear axle help the driver more easily maintain control on wet roads since deeper treaded tires are better at resisting hydroplaning.
If the front tires have significantly less tread depth than the rear tires, the front tires will begin to hydroplane and lose traction on wet roads before the rear tires. While this will cause the vehicle to understeer (the vehicle wants to continue driving straight ahead), understeer is relatively easy to control because releasing the gas pedal will slow the vehicle and help the driver maintain control.
However, if the front tires have significantly more tread depth than the rear tires, the rear tires will begin to hydroplane and lose traction on wet roads before the fronts. This will cause the vehicle to oversteer (the vehicle will want to spin). Oversteer is far more difficult to control and in addition to the initial distress felt when the rear of the car starts sliding, quickly releasing the gas pedal in an attempt to slow down may actually make it more difficult for the driver to regain control, possibly causing a complete spinout.
Tires should be serviced periodically following the rotation patterns provided in the vehicle's owner's manual or as established by the industry to help enhance wear quality and equalize front-to-rear and side-to-side wear rates. The minor differences in tread depth between tires that might be encountered immediately after periodic tire rotations at 5,000-7,500 mile intervals won’t upset the vehicle's hydroplaning balance and should not preclude rotating tires. For that matter, any differences in wear rates actually indicate that tire rotations should be done more frequently. Ideally tires should be replaced in complete sets. However when tires are replaced in pairs, the new pair of tires (assuming the vehicle is equipped with the same size tires all of the way around) should always be installed on the rear axle and the existing partially worn tires moved to the front axle.
This information can be found at http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=52
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