The race for ever shorter sidewalls and ever wider contact patches is nearing the limits of what is possible with Kumho's debut of a tire with a sidewall height aspect ratio of 15 in its new ECSTA SPT KU31. Designed for super-high-performance models like the Ferrari F430, Dodge Viper and Corvette Z06 or ZR-1, the tire also bears a tread width rating of 385mm, or just over 15".

That's a very, very wide tire, and that width is what makes the 15-series sidewall height possible. The numerical figures that determine a tire's size - in this case, 385/15ZR22, contain a wealth of information about its construction. The tread, or section, width of a tire is the first number. The sidewall aspect ratio is the second number, trailing the forward slash, and represents the height of the sidewall as a percentage of the section width.

In order to get a tire's sidewall down to just 15% of its width, a very wide tire is necessary for there to be enough material to provide for proper inflation, sidewall deflection over bumps and through turns, and adequate passenger comfort. Nevertheless, at just 58mm tall, the sidewall is about 50% shorter than that of a still fairly low-profile 275/40 tire.