Car Modifications Can Bring Some Unexpected Results

Dear Car Talk:

My son owns a 2019 Subaru WRX that he loves to modify. His first modifications included replacing his stock wheels with premium wheels with wide tires, adding coil-overs (thereby lowering the car) and "tilting" the wheels in at the top (not sure of the technical name!).

A few days ago, he was preparing to go to a Subaru festival. So he reinstalled his stock wheels (that had been stored vertically for two years in our cool, dry, dark basement) for the long drive, carrying his fancy wheels and his ramps and jacks inside the car, to be installed when he got to the festival. His stock wheels had essentially zero miles on.

He was driving along for about three hours when -- BAM -- he had a rear-wheel blowout. He doesn't think he ran over any road debris, and the blowout was on the inner side wall.

Is it possible the blowout was caused by the modifications he made to his car? The good news was he was able to change out all four wheels on the side of the highway and was back on his way in no time! -- Pam

It's more than possible, Pam. It's quite likely. That's what happens when you do wacky things to your car. But hey, at least he's not playing with Tide Pods, right?

There are two possibilities that come to mind. One is that the original tires have a different profile than his new tires. They're probably a little taller, for instance, with high sidewalls. So while the new tires worked when the car was lowered, the inner sidewall of the old tires may have ended up rubbing against the strut assembly or some other part of the rear suspension.

Or -- even if they weren't rubbing -- the tire was so close to something else that a big bump on the highway forced the tire into that piece and put a gash in it. If they were actually rubbing against something, he should see evidence of that on the other (stock) rear tire.

The other possibility is that he adjusted the camber (that's the term for whether the tires lean in at the top or out) to such an extent that the stock tires were practically running on their inside edges. Maybe one wore out that way. Or, since the sidewall is much more vulnerable to puncture than the tread surface, a road obstruction may have had an easier time damaging it.

The good news, as you say, is that he happened to have four spares, along with jacks and ramps in the back of his car. That was lucky.

So he's just going to have to travel like that from now on. And the good news for you, Pam, is that it'll clear up some storage space in your basement.


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