One of These Tires Is Not like the Others

Dear Car Talk

Dear Car Talk | Sep 27, 2019

Dear Car Talk:

I have a 2017 VW Golf that I purchased used. It had 8,000 miles on it.

I noticed one of the tires did not match the others. I figured it had been replaced because of damage. After about six weeks of use, I got a low tire pressure warning. Sure enough, the odd tire was the one that was low.

I had winter tires on for five months. The odd tire did not lose any air while it was stored. I switched back to my summer tires and sure enough, after about six weeks, I got a low tire pressure warning again --same tire.

The tire has been checked for leaks; none can be found. It appears to only leak when driving. It has been removed from the wheel and remounted, same results.

Any suggestions? -- Roger

It's not unusual for a tire to only lose air when it's being driven. When the tire is just sitting in the garage on its rim, off the car, it's not being deformed. It's not being subject to all the forces tires are under when the car is stopping, turning and going over bumps.

At some point, when that tire is deformed in a certain way, it's slowly losing air. Now, there's a very small chance that the wheel is at fault. If the tire had to be replaced due to damage, it's possible that damage was from a huge pothole that also bent the rim.

Perhaps the previous owner had the rim straightened, but there's still a slight irregularity. I trust your mechanic -- having dismounted and remounted the tire -- would have seen anything obvious. And the car is too new to have rust or corrosion around the wheel.

You can test the "wheel" theory by moving the suspect tire to another wheel. Swap a couple of tires to different wheels and then see if the leaky tire still leaks. By process of elimination (let's see ... you have the wheel and you have the tire), you can confidently conclude that it's a bad tire.

I'm pretty sure that's what it is, Roger. If it were my car, I'd skip the further experimentation and just invest $110 in one new tire. I think that'll fix it.

In the unlikely event that the leak continues on the new tire, bring a friend to hand you tissues to cry into when you go to price a replacement wheel at VW.

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