How Mismatched Tires Ruin Your Car and Destroy Tires

On the most recent episode of The AutoGuide Show brought to you by eBay Motors, we had a chance to sit down with Ian McKenney, Senior Product Manager for Bridgestone. We covered plenty of topics during the podcast, including why mis-matched tires are a bad idea.

“You should always make sure you have the same size tires in all positions of your car.” said McKenney, with the obvious exclusion being sporty cars that are staggered front to rear. “If you’re driving on different sized tires,” he continued, “one, it’s going to affect your driving feel and even being able to (properly) steer down the road. But you’re also inducing opportunities for some serious mechanical issues in your vehicle. Especially if side-to-side you have different sized tires, you’re going to cook a differential or something else pretty quickly.”

Using a gear-set, differentials are designed to allow an outside tire to rotate more than the inside tire during cornering maneuvers. But differentials are not made to compensate for two tires spinning at different speeds constantly. Larger tires spin slower than smaller tires as there is a larger circumference during each revolution of the tire. Differentials can overheat, wear out, or flat out fail under these circumstances.

But even if your differential survives, there’s other issues as well. As McKenney puts it, “If you don’t destroy your differential, you’re going to wear one tire down so quickly. (The tires) are going want to meet in the middle. They’re going to want to meet some level of equilibrium in terms of circumference of the tire.”

To reiterate his point, he reinforced “If you have a bigger tire on one side and a smaller tire on the other, if you don’t burn up the differential, you’re going to wear out the one tire until they match in terms of outside diameter.”

So, it’s important to not have mismatched tires. “If you have the ability, always change all four tires at a time. Have a matching set.” Said McKenney. But for those that can’t replace all four, he has another solution. “If you’re going to change tires, at least do it in pairs, side-by-side.”

Listen to the entire interview here.