Dear Tom and Ray:

There has been a recent upsurge of extremely low-profile tires and extraordinarily large-diameter wheels on all types of personal vehicles. Is this good: stiffer sidewalls -- less lateral movement? Or is this bad: more unsprung mass -- changing suspension requirements? Or is this just an expensive affectation? -- Frank

RAY: It's primarily about style, Frank. People want bigger wheels because they look cooler.

TOM: And if you use a bigger wheel, you have to use a lower-profile (i.e., shorter sidewall) tire so the wheel/tire combination still fits in the car's wheel well.

RAY: The weight isn't much of an issue, because alloy wheels are pretty light. And when you go with a bigger wheel/smaller tire combination, it's pretty much a wash.

TOM: You do get some handling benefits with lower-profile tires. The less-expansive sidewall you have, the less the sidewall will flex on turns. That's good for handling.

RAY: But you pay a high price in ride quality. Because you have less sidewall, there's less of it to absorb bumps and potholes. So lower-profile tires give you a much harsher ride.

TOM: The other significant argument against low-profile tires is that with less sidewall, the wheels
themselves are much more vulnerable to being bent from potholes and scraping up against curbs. Especially if you live in a city. And when you have to replace a 19-inch alloy rim and it costs you 750 dollars, you're going to wish you'd gotten the smaller wheels with bigger tires, even if you don't look quite as cool when you go to pick up your dry cleaning.