Low-profile tires, lousy driving a bad combo

Dear Car Talk: I bought a 2019 BMW 540Xi brand new. I love the car. But here is the problem: The car comes with run-flat tires and no place for a spare or jack.

I hit a pothole on the highway in the middle of the desert. Although the tires are run-flat, they recommend driving not more than 50 miles and at no more than 50 mph. Being much further than 50 miles from home, I needed to get towed into a dealer.

My question is, can I put regular tires on the car? Do I have to replace the wheels, too? The run-flat tires are low profile. Because of that, I have already had two cracked rims that needed to be replaced.

I would be happy to use the trunk for a spare, jack and lug wrench. — Don

Don: Yes, you can replace the run-flats with traditional tires, Don. And you don’t have to replace the wheels. You’d want to replace all four tires, rather than mix run-flats with non-run-flats. And then you’ll need a fifth one and an extra wheel to toss in the trunk as a spare.

I don’t know if you’d need to do any reprogramming to the tire pressure monitors, but your BMW dealer can answer that question for you since they sell this car with both types of tires. If I were you, I’d also ask your dealer to tell you the highest profile tire size that will fit on your car.

Your low-profile tires, combined with your apparent lousy driving, Don, are causing those cracked rims. Low-profile means short sidewall. And, because there’s so little sidewall between the road and the wheel, when you hit a pothole or drive up onto the sidewalk to park and get coffee, it’s very easy to dent or damage those rims. And, as you know by now, they’re extremely expensive to replace.

So, a higher profile tire will give you more sidewall and more rim protection. It’ll also make the ride more comfortable and quieter — as will the non-run-flat tires, by the way. The higher profile tires might make the handling of your 540Xi a tad less sharp, but at $1,000 a wheel, that’s probably a trade-off you’re ready to make.

Dear Car Talk: My question is not about the mechanics of a car, per se, but about the use of certain types of vehicles.

What is the actual purpose of so many new vehicles sold with outrageously high horsepower ratings, like 500 horsepower or more? Some are now in the 700-horsepower range.

Why? For what reason? Bragging rights? We all know that those high horsepower vehicles cannot even begin to use their potential legally on public roads. Are they being taken to a track? Are they hauling loads as heavy as a house?

Those horsepower ratings to me are so ridiculous that I find them humorous. Am I missing something here? — Paul

Paul: It’s as old as human history, Paul. Trying to compensate for an inadequacy elsewhere.

If I were writing a newspaper column during the Paleolithic Era, I have no doubt someone would write to me asking why some cavemen feel the need to have such enormous clubs. “They can hardly swing them!”

That same desire to stand out and signal that you’re “more powerful” or “better able to provide” has always played out in the car market.

And, rather than try to fix this genetic human vulnerability, car companies said “Hey, I bet we can use this to sell more Dodge Chargers!”

So, you’re not missing anything, Paul. The vast majority of people who buy overpowered cars don’t go to the track. And there’s very little they can do with these cars on public roads, except show off for half a block. But on some level, they believe that driving a more powerful car makes them more powerful.

And don’t expect the horsepower race to slow down with the introduction of electric vehicles.

When EVs first came out, they were seen as economical appliances. But the auto industry, which has 100 years of experience selling cars, figured out that it’s a lot easier to sell an EV if it’s not only cleaner and quieter but also faster.

So now you’ve got the Lucid Air with 1,100 horsepower and a 1,000 horsepower Tesla Model S.

And I have to admit, it is kind of fun to step on it once, just to feel your lips peel back to your ears.

To be fair to EVs, it’s much easier to make tons of power with an electric car. The motors are simpler, and the power delivery is far more direct and efficient.

It’s not like an internal combustion engine, where you have to suffer with 7 miles per gallon to carry the weight of a 700-horsepower engine around. The penalty you pay for power in an EV is much, much lower.

So, these “power wars” are going to be with us for the long haul, Paul. Fortunately, when our modern-day cave men get lured over to EVs, at least they’ll be making less pollution and noise.

Got a question about cars? Write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at www.cartalk.com.

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