Tire Wear: It May Not Be Where You Think It Is

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Most cars will have the same sized wheels in all 4 positions. Ideally, they should all be the same type of tire with the same design. This means that if you buy new tires, they should be of the same design and from the same manufacturer. They should also be inflated to the proper pressure. And the tire wear should be the same for all tires. All of this will give a vehicle optimum handling.

But the reality is that the front tires are responsible for most of the handling. They transmit acceleration, steering, and braking on front-wheel drive cars. Because of this, the tire tread wear on front tires is greater than that of back tires.

Therefore, to prevent uneven tire wear on your front tires, you need to get them rotated. If they are not rotated, the tire tread wear will reduce your tire to about 1/2 the original tread depth.
If this occurs, your gut might tell you that since the front tires wore out first and because there is still about half tire tread depth remaining on the rear tires, the new ones should be installed on the front axle. Thus, you might conclude that when the front tire tread depth goes down half again, then the back tires will be worn out too at that time.

But in this case, your gut is wrong. And it could be dangerous.
What you have to do is install tires that are new on the rear axle and move the worn back tires to the front. Tires that are new installed on the back will actually help you maintain more control on wet roads because the deeper tire tread depth will be more resistant to hydroplaning.

What is hydroplaning?

Hydroplaning is when the tire cannot process enough water through its tread design to maintain enough contact with the road. In moderate to heavy rain, water can pool up in road ruts. When traveling at higher speed, the tire’s ability to deal with these pools of water tests whether the tire can effectively resist hydroplaning.

Hydroplaning is caused by a combination of things. This includes: water depth, vehicle weight and speed, as well as tire size, air pressure, tire tread pattern and tire tread depth. For example, a lightweight vehicle will hydroplane at lower speeds in a heavy downpour if it has wide, worn-out, and under-inflated tires than a heavy vehicle would in drizzling rain with new and properly inflated tires.

If the rear tires have more tread depth than the front tires and the car begins to hydroplane, then the front tires will begin to hydroplane on wet roads before the rear tires. And because most vehicles are front-wheel drive, the vehicle will understeer. This is not good, but it is easy to control.

All you have to do is release the gas petal and the slowed speed will help you to regain control of the vehicle.

If it’s the other ways around, however, this is a more serious problem. In this case, the rear tires will begin to hydroplane before the fronts. This will cause the vehicle to begin to oversteer. This means that the vehicle will want to spin. In this case, slowing don the car can actually make it worse.

At Michelin's Laurens Proving Grounds, we had a chance to experience this first-hand. Those who participated drove around a large, wet curve in vehicles fitted with tires of different tire tread depths. One vehicle had tires that are new on the rear and half-worn tires on the front, and the other with the tires that are new on the front and half-worn tires on the rear.

The results proved what we had been thinking all along. In the cars with tires that were new on the front, we felt the helplessness when we tried to control an oversteer. But we were able to take control during an understeer.

Our drivers knew we were going to be challenged to maintain car control, but despite that fact, spinouts were common during laps in the car with the new front tires. And Michelin tells us that almost everyone spins out at least once!

We’ll take the spinouts at Michelin's Laurens Proving Grounds rather than in traffic on an Interstate ramp in a rainstorm any day!

Bottom line: when changing tires in pairs, put the new ones on the rear and move worn ones to the front.