Do I need to change all four tires at the same time?


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Have you ever wondered whether it was OK to replace just one or two tires instead of replacing all four at the same time?

Highly rated auto experts on Angie’s List say in most cases it’s better to replace all four, for a number of reasons. However, some mechanics say it’s OK to replace two if you’re under budgetary restraints, or depending on the tread level of the two tires you plan to keep on the vehicle.

“I do not recommend changing them in pairs unless you have replaced tires in pairs within six months [of each other] due to financial reasons,” says Craig Knarich, owner of highly rated Pit Crew Tire Service in Palm Harbor, Florida. “If you only replace two, oftentimes you’re not going to remember to replace the other two.”

Why you should replace all four tires at once

Knarich says in most cases, drivers aren’t going to find a “match set” of tires with the same tread as the older tires, if they’re looking to pair two new tires with two old ones 

Knarich adds replacing a pair of tires will leave your car with two tires with superior traction and two tires with mediocre traction.

One danger of not replacing all four is if the older tires in the front are bald, they have no traction, making it difficult to turn the car in rainy conditions.

Tim Haynes, with highly rated Direct Tire & Auto in Watertown, Massachusetts, says all four tires should always be replaced if they’re worn out. 

Auto experts say buying only two new front tires can increase the change of fishtailing or hydroplaning. Different-sized tires can also unbalance the car’s suspension.


Tread matters

Deciding how many tires to replace can be downright mathematical. Haynes says it depends on several factors, including the vehicle’s type.

For all-wheel and front-wheel drive vehicles, he says all four tires must have the same tread design and be of the same make and model. 

“Different tread patterns and compounds deliver different levels of traction,” Haynes says. “On these vehicles equipped with a differential, the variation of tread will overwork the differential and drivetrain and can cause serious damage.”

An important note to consider, Haynes says, is that if you only switch out two tires, all four tires should still have tread depths within 4/32 inches of each other.

“Tires with different tread depths will rotate at different RPMs,” he says. “A differential works to distribute power to wheels that are slipping, and the difference in RPMs can cause the differential to think this is happening.” 

For example, Haynes says is if a customer comes in with front tires with a tread depth at 8/32 of an inch and rear tires at 3/32-inch depth, he would recommend replacing two tires. This is because leaving the front tires with a tread of 8/32 on and putting new tires on with a tread of 11/32 would create a 3/32 variation, which he says is acceptable. 

“If the customer had two rear tires at 3/32 and the fronts at 5/32, I will be recommending four new tires,” he says. “This is because the replacement of the two worst tires will leave us with 5/32 and 11/32. This [difference] is too vast and can risk differential damage.” 

Haynes recommends four matching tires on the car at all times. Some tire stores may not have a set to match the two tires you wait to replace.


Rotate your tires frequently 

If you’re on a budget, Knarich says there are times you can get away with buying two new tires. In these cases, the new tires should be placed on the back of the car for better steering. If the better set of tires that you’re not replacing is on the back, have your mechanic move those to the front. Drivers should also be diligent, Knarich says, about rotating tires every oil change — or 3,000 to 5,000 miles — to keep the tread wear as even as possible. 

Haynes, meanwhile, recommends rotating tires every six months or 6,000 miles. 

“This is not only important to prevent uneven tire wear between the front and rear tires, but it’s also important to prevent voiding any mileage warranties offered by the tire manufacturers,” he says. 

Haynes also recommends having the car’s alignment checked every 12 months or 12,000 miles, even if the car is driving straight. Vehicles off alignment can cause serious tire wear. 

“When replacing two tires, it’s recommended to rotate the new tires to the rear and to align the vehicle,” Haynes says. “When replacing all four tires, the alignment should also be performed to ensure the new tires will wear properly, and the new vehicle will handle as it should.”


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This article was written by Tom Moor, Angie’s List.

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