Q: I'm a 70-year-old woman with a 2016 BMW 228i xDrive coupe, base model. The current tires are the Continental run-flats that came with the car. I need to replace the tires and have a few questions:

Although the front tires are worn out, the back ones have some tread left. Must I replace those, too?

Someone mentioned that I might have "staggered" tires. I don't know what that means or how to determine if I do.

I've always liked Michelins, and they have both Y-rated tires and V-rated tires. What does that mean, and which ones do I need?

Do you still recommend rotating the tires? Some places will do it for free if I go back there regularly. And should I rotate them just front-to-back or also in an X?

Sorry for so many questions.

A: I'm tempted to do what my kids do to me. When I text them a series of questions, they just answer the last one and pretend they never saw the others.

First of all, you do need four new tires. You have an all-wheel drive car, and in order to avoid doing harm to your center differential, you need four tires that are all the same diameter. Worn-out tires will have a smaller diameter. So replace all of them.

If your rear tires are wider than your front tires, they are considered staggered, and you'll need to buy two wider tires for the rear wheels. How do you know if you have staggered tires? On the sidewall, you'll see the tire's measurements. The number to look for is the tire's width. That's a number given in millimeters like "195" or "225," and you'll find it inside a string that looks something like "P225/55R18."

(By the way, we looked up the specs for your car and you don't have staggered tires.)

The letter (Y, V, etc.) is the tire's speed rating. And unless you're a closet Lightning McQueen, you don't need to spring for Y- or V-rated tires. Y-rated tires are good up to speeds of 186 miles per hour. V-rated tires are good up to 149 mph.

While there's no harm in having tires that are rated for a much higher speed than you'll ever drive, you'll pay extra for those exotic tires. An H-rated tire (130 mph) will be more than adequate for your purposes.

As for which brand to get, Michelins are very good tires. But you can buy anything that's the same size as the tires you're replacing.

Once you get your new tires, we do recommend rotating them front to back. (Especially if it's free!) Your current front tires wore out faster than your rear tires because front tires do most of the braking and all of the steering. If you rotate your next set every 5,000 or 7,500 miles, they'll wear more evenly, and the whole set will last a little longer.

Problem solved

Q: Driving from Michigan to Yellowstone National Park, my 2015 Subaru Outback made a rhythmic noise that increased with speed. Upon our return, the dealer discovered that we had defective wheel bearings in both front wheels. New parts were installed, but now I worry: Could the damage caused by the heat buildup affect other parts of the car?

A: No, you're fine. Although you might consider meditation for the Outback anxiety you've developed.

The wheel bearings allow the wheels to spin. They're made of cages with ball bearings in them. If a bearing fails, it gets hotter because of the friction. That's what happened in your car. But a wheel bearing is a self-contained unit. Nothing else around it would be harmed.

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