Partially valid: having different diameter tires can lead to lash or noise in the drivetrain, but that extra noise/stress depends on the diameter difference. Y

Partially valid: having different diameter tires can lead to lash or noise in the drivetrain, but that extra noise/stress depends on the diameter difference. You're not going to HAVE to buy all new tires if you have a blowout and need a new one. Your drivetrain won't explode if you put on a new tire with three used ones. Decent tire shops are able to shave tires to match the rest of the set if there's a big difference.