Replacing 1, 2 or 4 tires on AWD and 4WD

A new tire is slightly bigger around than a worn one of the same size, because of the extra tread. The difference is small, but it means the new tire turns fewer times over the same distance.

Why that matters on AWD and 4WD

These vehicles have extra differentials or couplings that let the wheels turn at different speeds for a moment, in a corner or when one wheel slips. They are not built to do it all the time.

Mismatched tires make them do exactly that, every kilometre, even in a straight line. The parts run hot and wear early. The traction control can also read the difference as wheel slip.

How close is close enough?

It depends on the vehicle. Some makers want all four tires within 2/32" to 4/32" of tread depth of each other. Others give a limit on the difference in circumference. Your owner’s manual has the number for your vehicle, and it is worth reading before you buy.

What to do

• Best: replace all four with the same brand, model and size.
• Two tires: check the tread depth on the other pair against your vehicle’s limit first.
• One tire: usually only works if the other three are close to new.
• Rotate on schedule so all four wear at the same rate and can be replaced together.

Not sure where your tires stand? Bring the vehicle in and the team will measure the tread on all four.