One benefit to having tires rotated is that someone gets up close and personal with the tires and can check them out to see if there appears to be anything wrong with the car.
Some years ago, I took the car in for its annual rotate and balance, and it may well have saved my life, or at least saved me a huge inconvenience and spared the life of the car as when they took off the fronts, there was exposed belting on the inner sidewall caused by failed tie rod ends, and the tires and/or the tie rods weren’t all that far away from a catastrophic failure.
I have a car with unidirectional tires and different sizes front vs. rear, so no rotation.
I have a pick-up truck with five full-sized tires and I do a five-tire rotation. I am at 98k on the original tires. Had I not rotated, the spare would have been wasted (dry rot), and I would have had the “pleasure” of going to a tire shop to get 2 tires and be told my spare was junk, too.
I am going to get a much better deal on five new tires and know they will all be used.
I’d like to add that there are quite a few shops that offer lifetime rotation for free for tires you bought through them. I know it’s a bit of an inconvenience, but if you want to rotate your tires regularly, that’s the way to do it. If you get your oil changed by the same garage, just have them rotate the tires too.
There’s also an issue of safety. Most people I think don’t keep their tires till they are bald. You are more likely to allow your front tires to get too bare if you don’t rotate your tires. And it’s cheaper for you (in the short term) to just rotate your tires.
Also, you can sell your used tires if they still have tread on them.
Not true, notice I said “in an emergency”. As tires get older, they become more brittle and provide less traction. If you have, say a set with 30k on one end, and brand new ones on the other, it will affect the car’s handling. If you have to turn and brake severely at the same time. The older tires are not going to grip as well; causing understeer if the old tires are on the front, and oversteer if they are on the rear. I autocross frequently, and just changing the tire pressure by just a 2 pounds affects this behavior. The age of the tires are just as important for your vehicle to behave consistently. If you’d rather take that risk to possibly save a few dollars, go ahead. I personally don’t think that you’re saving a penny by not rotating your tires (I rotate them myself, so it is free), and haven’t seen any reliable evidence that it does.
If your tires are brittle and need to be replaced, then they need to be replaced. Notice that I said, “If they’re still good.” You wrote there’s an issue “with buying only 2 tires is that now you have older, less grippy tires on one end, and new, grippy tires on the other.” That’s not an issue “If they’re still good”. Having tires on your car that have become brittle is.
The point is that even though the older tires might still be “good,” they will perform differently than new tires due to age and wear. They might not be falling apart brittle, but they are still more brittle than the brand new tires. By rotating your tires, you avoid a situation where you’re tempted to keep those older tires “because they’re still good” because all four tires have worn down equally.
So? What’s the point now? If they’re still good, i.e., shouldn’t yet be replaced, why would you replace them? Because they won’t perform the same as new tires on the other end of the vehicle? No, you don’t replace them unless you enjoy wasting money.
When tires have become noticeably brittle, you replace them. I suppose one year old tires are “more brittle” than brand new ones, but so what?
I’ve never advocated not rotating tires. Why wouldn’t you be tempted to keep tires that are still good? You should be; that’s not a situation to be avoided.
If I rotate my tires, they all wear out evenly and I replace them all at the same time. The idea of only replacing two doesn’t even factor into the equation.
The advantage to replacing them all at the same time is that a car with uneven tires does not handle as well as one with evenly worn tires. In the interest of safety, I would like my car handle as well as possible.
For the sake of arugment, if I bought a used car and it had two good tires that were only a year or two old and two that needed to be replaced, I’d probably just get two new ones and then adjust the rotation timing to try and get them into sync. But if the “good” tires were more than 3 years old I’d just get a whole new set.