Hobbies Cars & Motorcycles Tire Time! How to Figure Out What Size Tires You Need Tire Size Matters Share PINTEREST Email Print Jetta Productions/Getty Images Cars & Motorcycles Cars How Tos Buying & Selling Basics Reviews Tools & Products Classic Cars Exotic Cars Corvettes Mustangs Tires & Wheels Motorcycles Used Cars SUVs Trucks ATVs & Off Road Public Transportation By Matthew Wright Matthew Wright has been a freelance writer and editor for over 10 years and an automotive repair professional for three decades specializing in European vintage vehicles. our editorial process Matthew Wright Updated September 03, 2017 There is so much room for adjustment in terms of tire size that it would take an encyclopedia to list them all. Luckily, you're smarter than the average tailgater, so here are some tools to decide for yourself. You should also learn how to read your tire. Tire Width A wider tire will give your car better grip on dry pavement, but your gas mileage will suffer. Too wide and your tires may rub your car's body, destroying the tire. Narrow tires are better for traction in winter weather. But go too narrow and you're creating a safety risk. Your car relies on how much rubber touches the road to keep you going in the right direction. Unless you're trying to do some serious experimenting or you are being advised by a pro, you should always go with the size tire the auto manufacturer suggests. Aspect Ratio A tire's aspect ratio determines how tall the sidewall is. A lower, stiffer sidewall will greatly improve cornering but will make your car's ride a little harsher. That's why a Cadillac has a nice big bubble tire while a Porsche looks like somebody put a black rubber band around the rim. Changing the aspect ratio too much can throw your speedometer off, which is why some people go a Plus-One setup. This way you have the benefit of solid cornering and you'll know how fast you're going. Wheel Diameter This is pretty much non-negotiable. If your car has 16-inch wheels, you'll need 16-inch tires. The only way to change this is to buy new wheels, for instance, if you were going with a Plus-One or even a Plus-Two setup.