Tires: Your Biggest Bang for the Buck

You can do the math. The formula for overall tire diameter is [(width x aspect ratio) X 2] + wheel diameter in millimeters. (Multiply by 25.4 to convert inches to millimeters.) A 225/55R16 has a nominal outside diameter of 654mm. A 225/50R17's OD is 657mm. Close enough. If you want a wider tire, a 245/45R17's diameter is 652mm. To stay with the same wheels but get a wider tire, a 245/50R16 will be the same diameter as the 225/55R16. Measured with a ruler, the sidewall height of the 225/55R16 is the same as that of the 245/50R16—it's the relationship of width to height that's changed. Note that these are "nominal dimensions." One tire company's 245/45R17 may be slightly larger or smaller than another company's of the same nominal size.


A lower aspect ratio tire of the same brand and model will increase how quickly your car responds to steering input (and, thus, handling feel), but it probably won't improve extreme grip. For that, you'll need to upgrade the tire type.