What Difference Does Wheel Size Make?

The aesthetic appeal of larger wheels and tires is undeniable but what about the performance benefits? Larger wheels give cars a more aggressive stance and greater stage presence, which is why king-size rims are installed on concept cars by automakers. They make it look cool.

Whether you move to a larger diameter wheel as an option on a new vehicle or as aftermath wheels for the car you already own, there are positive sides to plus sizing but negative sides as well. When you move to a larger wheel diameter, such as from 17 to 18 inches, you need new tires to match. Those tires need lower profile or sidewall height to maintain adequate clearance when the car goes over bumps and potholes, which makes the suspension fully compress and rebound. When a wheel diameter increases by even just an inch, the height of the tire should decrease as well in order to keep the overall diameter the same.

For example, if the original stock tire is 215/65R17 and you buy 18 inch wheels, the right size for the larger rims would be 225/55R18, with the differences being the larger diameter wheel size, wider tread and lower profile – 55 instead of 65. The height of the sidewall is 55 percent of the width of the tread.

You will run the risk of damaging the suspension of your wheels and tires and you’ll also get incorrect speedometer readings if you change to larger wheels without taking sidewall height into consideration because the wheels are turning at a different speed than before. With larger wheels and lower profile tires, they’re stiffer and theres less of an air and rubber cushion than before, increasing the chances that hitting a large pothole or bump could damage the tire, wheel or both.

A performance benefit may be offset by the additional weight of the larger tires and wheels. An 18 inch tire will weigh more than a 16 or 17 inch tire. A steel wheel weighs more than an aluminum alloy wheel, so the latter enhances performance by reducing the unsprung weight. But replacing a standard 17-inch allow wheel with an 18 or 19-inch alloy rim will add weight unless its an expensive, lightweight type.