How to Choose a Different-Sized Wheel and Tire Combination
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When it’s time to replace your car’s tires, the natural move is to stick with the same size. Many drivers choose a tire from a different brand for better all-weather grip, handling, or braking performance, based on a recent Consumer Reports survey. But replacing both the wheels and tires can make sense for some drivers who want much better performance.
A common situation in which you’d change sizes is when buying winter/snow tires. Retailers often recommend moving to a smaller wheel and using a tire with a taller sidewall, without increasing the overall tire diameter. This creates a longer footprint, also known as contact patch, where the tire connects to the ground. A longer contact patch can help snow traction. (However, a wider tire hurts winter traction by plowing through snow or even floating on top, akin to hydroplaning through a slushy.)
Or you may want to upsize to a larger wheel and a tire with a shorter sidewall. This can be done because it’s fashionable and to improve three-season handling—a short sidewall has less roll and such lower-profile tires are typically optimized for grip.
Putting performance aside, you may just want to switch to a more common wheel and tire size for the sake of availability and cost if you plan to hold on to a car for at least a couple tire changes. Before making such a change, there are several things to consider.
For a wheel to fit properly, it needs to have the right lug nut holes and offset—the distance from the recessed hub mounting surface to the center of the wheel.
The replacement tire should have an overall diameter that closely matches the original rubber to ensure that the speedometer, odometer, and overall vehicle dynamics aren’t affected.
The replacement tires should have the same load capacity or higher to ensure they are rated to carry the same weight. The load capacity index can be found on the tire sidewall. It’s a two- or three-digit number after the tire size. (Learn more about reading a tire sidewall in our buying guide.)
Tires are commonly split between metric tires for car and crossover vehicles, and LT, or light truck, tires. (An LT tire is built for more demanding applications and costs more because of its tougher construction.) The key is to be sure the tire is engineered for your vehicle’s demands and load.
For all-season tires, use a tire with the speed rating recommended by your vehicle owner’s manual or listed on the tire information placard found on the driver’s doorjamb. This letter denotes the maximum sustainable speed and is found directly after the load index. Standard all-season tires are usually rated S (up to 112 mph) or T (118 mph). Climbing up the scale are the letters H (130 mph), V (149 mph), W (168 mph), Y (186 mph), and ZR (149+ mph). Though few drivers would ever drive to these sustained speeds, higher speed-rated tires generally offer better handling and wet grip than lower-rated tires. Generally, you may go up to a higher speed rating than the original tires to improve performance or move to a lower speed rating for winter/snow tires, but consult your vehicle owner’s manual for specifics.
It may seem daunting to sort through these different factors in selecting alternative wheels and tires, but tire manufacturers, local car dealers and tire shops, and online tire retailers can help. Not being adequately informed before you switch to a different wheel and tire combination can lead to the speedometer being inaccurate, the vehicle not handling properly, and the brakes not working as designed.
It’s important to seek professional advice for your specific needs and vehicle to ensure proper fit. The wheels, for example, can have a compatible bolt pattern, but the offset or smaller diameter might not provide proper clearance for the brakes.
How to Identify a Compatible Tire Size
Changing one size up in tire width and one size down in aspect ratio (the ratio of the tire sidewall height to width) will maintain approximate tire size. As an example, a P195/60R15 has an overall diameter of 24.2 inches and a load capacity of 87. Move up to a wider tire with a lower aspect ratio, P205/55R15, and the overall diameter is similar, at 23.9 inches, and the tire has the same load index of 87. In reading the tire sidewall, the aspect ratio is expressed in the center number, 60 and 55, respectively.
Online tire size calculators can be helpful when choosing alternate tire and wheel sizes.
Some tire size calculators give the size tire available for a specific make and model car. Consumer Reports’ tire selector tool can do that, plus it lists other sizes that are available for that car model and highlights compatible tested tires.
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Top pick tires for 2016
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