Car Talk

Dealership’s service department earns C average

Ray Magliozzi, syndicated columnist

Dear Car Talk:

After getting dealer service on my 2016 Toyota Corolla with 16,000 miles, the car started to shake at 60 mph. I drove for a couple more months, but the shaking did not go away.

I finally checked, and the tires were over-pressurized to 51 psi, 19 psi higher than indicated on the door pillar. The dealer evidently inflated the tires to what was the maximum pressure indicated on the tire itself, rather than the recommended pressure.

A couple of questions:

1. Should I replace a 7-year-old set of tires with very low mileage on them? The treads are almost brand new.

2. Could over-pressurizing an old set of tires result in the wheels needing to be rebalanced?

Thank you so much, Ray! — Sam

I’m less worried about your tires than I am about how many fillings you lost driving with tires filled to 51 psi.

Let’s start with your high-speed shaking. Inflating tires to their maximum allowable pressure will not damage them or cause a vibration. But it will cause a very hard ride.

The most likely explanation for the vibration is that your tires were so overinflated that when you hit a pothole, the hard impact knocked off a wheel weight or two, causing your tires to go out of balance.

Should your tires be replaced at 7 years old? Probably. Your dealer is right that over time, the rubber will start to degrade, even if there’s still useful tread left.

Why does that happen? Mostly because ozone in the air degrades rubber.

But even if you assume they’re erring on the side of caution (and tire sales), I think 7- or 8-year-old tires should probably be replaced.

So, your dealer gets a grade of “C” overall. “A” for his information on replacing older tires, and “A” for knowing that maximum inflation would not have caused your vibration. But we’re going to dock him for letting you drive away with 51 psi in your tires. …

EDITOR’S NOTE: Got a question about cars? Email to Car Talk by visiting the Car Talk website at www.cartalk.com.


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