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Why Do Lug Nuts Swell

Dear Car Talk:

My wife’s car is a very well maintained 2015 Lincoln MKZ. It has only 34,000 miles on it. After a routine oil change and tire rotation last week, the dealer service writer said that it was difficult for them to rotate the tires because we have a situation with “swollen lug nuts.”

He strongly recommended that we have them swapped out, at a cost of nearly $100. A quick Internet inquiry verified that this is indeed a real issue in recent years with Ford and other manufacturers.

As a 66-year-old who is still a teenager at heart, I admit that I had to initially suppress a giggle at the “swollen lug nuts” diagnosis.

But, I quickly realized that this could be a dangerous and/or expensive thing. What if we were to get a flat tire far away from home, and I was unable to remove the wheel?

Shouldn’t Ford have issued a factory recall on this? I guess purchasing new lug nuts is the way to go, but how do I make sure to get the right size, and that the new ones will not be susceptible to swelling, too?

Any suggestions?

— John

You’ve come to the wrong columnist, if you want me to condemn you for giggling.

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Anyway, yes, it’s a real thing. And you should address it. The dealer will have the right size replacements for you. The problem is that the lug nuts themselves are steel, but they’re covered on your car in a thin chrome veneer — because I guess some people prefer shiny lug nuts.

Over time, water gets trapped in between the steel and the chrome cover, and the steel starts to rust (especially if you live in a place where they use a lot of road salt). That rust pushes up against the chrome cover and enlarges it, and all of a sudden, you can’t get your lug wrench over it.

Now, if you’re at a repair shop, they can just use a socket the next size up, and it’s not a big deal. But, if you run over a petrified armadillo in rural Texas and get a flat tire, you’ll only have one wrench with you. And, it’s not going to fit.

So, yes, it’s unfortunate that this happens. But my advice is to just spend the $100 and try to balance that out with a good laugh, John.

Post questions online at CarTalk.com.(c) 2022 by Ray Magliozzi and Doug BermanDistributed by King Features Syndicate Inc.

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