Tire Wear Report: Unintuitive Installation Is The key To Even Wear

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In most cars, you will have same-sized wheels in all 4 positions (front, back, left, and right). In ideal circumstances, they should all be the same type of tire with the same design. So, if you buy new tires, they should be of the same manufacturer and the same design. In addition, they should also be inflated to the pressure recommended in your vehicle’s owner’s manual. And to give a vehicle optimum handling, the tire wear should be the same for all tires.

But it is important to remember that the front tires are the tires that are responsible for most of the handling. They are the tires that are transmitting acceleration, steering, and braking on front-wheel drive cars (which most cars are). Due to this, more than back tires the tire tread wear on front tires is greater.
So, if you want to prevent uneven tire wear on your front tires, you’ll need to get them rotated. If you don’t rotate them, the tire tread wear will reduce your tire to about 1/2 the original tread depth.

When this occurs (and it does fairly often happen), your intuition might tell you to replace the front tires with new ones. It seems to make sense since the front tires wore out first but there is still about half tire tread depth remaining on the rear tires, the new ones should be installed on the front axle. It would lead most people to 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 it’s been proven time and time again, that this “intuition” is dead wrong, and it could make you dead in the process.
Let us explain. The proper action to take is to do is install tires that are new on the rear axle and move the worn back tires to the front. New back tires will actually help you maintain more control on wet roads. This is because the deeper tire tread depth will be more resistant to hydroplaning.

What’s the big deal about hydroplaning?

What is hydroplaning? Good question. Hydroplaning, simply put, is when the tire cannot process enough water through its tread design that it cannot maintain enough contact with the road. In moderate to heavy rain, water tends to pool up in ruts in the road. And when you travel at higher speed, it is the tire’s ability to deal with these pools of water that can test whether the tire can effectively resist hydroplaning.
What causes hydroplaning is a combination of things. Some of these things include: water depth, vehicle weight and speed, as well as tire size, air pressure, tire tread pattern and tire tread depth.

How tire installation affects hydroplaning

In the case of the rear tires having more tread depth than the front, the front tires will hydroplane on wet roads before the rear tires. And because most vehicles are front-wheel drive, the vehicle will understeer. This means the car wants to still go forward. This is a scary situation, but it is easy to regain control.
To regain control, just release the gas petal and slow down. This will help you to regain control of the vehicle.
If you have new front tires, however, it can be a more serious problem. In this case, the rear tires hydroplane before the fronts, causing the vehicle to oversteer—meaning the vehicle will want to spin. In this case, if you slow down the car it can actually make it worse.

We had a chance to experience this first-hand at Michelin's Laurens Proving Grounds. The participants got to drive around a large, wet curve in vehicles with different tire tread depths on the tires. One vehicle had new rear tires and half-worn front tires, and the other had new front tires and half-worn tires on the rear.

The results were conclusive. The cars with new front tires oversteered, giving us a feeling of helplessness when we tried to control it. But in the cars with new rear tires, we were able to take control during an understeer.

In addition, unlike drivers on the road, our drivers knew we were going to be challenged to maintain car control. But despite this before-hand knowledge, spinouts were common during laps in the car with the new front tires. Michelin tells us that almost everyone spins out at least once!

Luckily for us, the spinouts took place at Michelin's Laurens Proving Grounds rather than in traffic on an Interstate ramp in a rainstorm!

Conclusion: If you are going to change your tires in pairs, put the new ones on the rear and move worn ones to the front.