Give 'Em an Inch

Sometimes a small difference in wheel width can make a big difference in performance.

One might think that with a racer of Tom Long's experience, there's little new to learn on the race track. But while conducting testing for the 2016 Global MX-5 Cup car, he surprised himself with what a difference an inch in rim width made when the tire size doesn't change.

"The rim width affects the tire's contact patch," he explains. "So we're playing with that, and the car acts different and has different characteristics on a stock rim vs. a wider rim. From a racer's standpoint, I like the wider rim. Not only because it goes faster, but has better feel in braking and cornering and just overall grip and confidence."

In choosing a tire and wheel combo for the Global MX-5 Cup car, fast wasn't the only consideration – component life was a key factor to consider, along with the expense of consumables. But for many racers, fast is the primary, if not the only, thing that matters. Rules matter as well, of course, so for many racers that may be the limiting factor. But where there's some freedom to choose wheel and tire sizes, how they affect each other and work together is worth considering.