Will really wide tires make you faster? | Nankang CR-S Tire Test

History Lesson

Back when GRM was called Auto-X magazine, the first cover car was a 240Z sporting 13-inch wheels. Back then, 175/70R13 tires were a thing. That was a high-performance fitment in 1984.

Soon thereafter, 185/60R14 was state of the art, followed quickly by 195/50R15, 205/50R15 and eventually 225/45R15. Matching wider wheel widths followed each of these sizes, with 15x9 being the widest to support those 225s.

As Hoosier entered the R-comp revolution, it pioneered even wider 15s: 245/40R15, 275/35R15 and even 295/30R15. Wheels followed suit: 15x10, 15x11 and even 15x12. Fenders were cut and flared, and abundant grip was had by all.

But when SCCA moved to street tires for most of its classes, the widest available fitment in a 23-inch-tall tire was reset back to 225. Competitors clamored. Eventually, Nankang, Falken, Maxxis and BFG all responded with 245/40R15s, but nothing more.

This was enough to satisfy most of these underpowered vehicles until the introduction of the XS and Max categories in autocross and time trials, respectively. These feature high-powered, run-what-ya-brung machinery, limited only by the use of a street tire. Suddenly, calls were heard for even wider 15-inch street tires to put down the big power these beasts could produce.

Over a year ago, Nankang finally heeded those calls by adding the 275/35R15 size to its Sportnex CR-S V2 line. But just as the new tire was ready, the market for it disappeared–due to a debilitating importation situation that kept new stock out of the U.S. for almost a year. That’s all been repaired now, and fresh Nankang rubber is once again available at the usual retail outlets, including in the new size.

[Tested: How does the new Nankang Sportnex CR-S compare?]

For our test, we also lined up a set of 245/40R15 Nankangs as well as a set of 225s, the latter already having some wear thanks to a previous test. They had been properly stored, though, while the numbers said that they were still in their prime.

From left to right: 275/35R15, 245/40R15, 225/45R15. Photograph by Andy Hollis

As we’ve shown in multiple previous tests, wider tires are rarely quicker without wider wheels, so each tire was mounted on an optimal wheel width for that size: 225mm tires on 9-inch-wide wheels, 245s on 10s and 275s on 11s. Those last two fitments can be especially tricky to install over big brakes and without rubbing fenders. Offset and barrel design have to be perfect.

[Wheel width: Is wider always better?]

Enter Good-Win Racing. The company has been doing Miata parts development and retail sales for decades. In particular, the folks there have become experts in fitment of various wheel-and-tire combos from multiple brands. For each generation of Miata, they’ve done the homework to show what can fit with various levels of wheel well and brake mods. In many cases, they have worked directly with a manufacturer to produce a wheel with dimensions that provide the ideal wide fitment.

In our case, both the 15x10- and 15x11-inch wheels are exclusive Good-Win offerings built by Konig. While designed originally for the NB generation, these two Dekagram models have massive brake clearance that allows them to fit over the Brembos on our Triple Threat ND Miata test mule.

Photograph by Andy Hollis

We did have to roll our rear fenders to accommodate the 275s, though. The result? Hella flush when cornering.

Both sets of new tires were given the usual initial heat cycle with six track laps of increasing intensity, bookended by highway drives to and from the track. While the 245s felt fairly normal on the road, the 275 steamrollers tramlined quite a bit, following every highway rut and undulation. Handling was also darty, requiring constant attention to the wheel.

​​​​Photograph by Timothy Harper

Test day at Harris Hill Raceway dawned in the low 80s and would climb close to 90 while we worked under the partly cloudy skies. The track was in great shape, having hosted an SCCA Track Night in America the evening before, but we still did a practice session to dial in our driving. After a short coffee break to let the tires cool, we turned on the lap timer.

We ran through each set of tires at 30-minute intervals, eventually circling back to the leftover 225s, hoping to see similar pace at the end.

*Prices current with Tire Rack as of June 24, 2025.

As all of our tires were the same model, you might expect them to have the same heat characteristics, but tread depth and age played a major role here. As we’ve seen in previous test stories, most street tires gain both pace and session consistency as the tread wears down.

Indeed, our year-old 225s used as a bracket tire were extremely consistent during the second session. During the opening effort, however, we saw an increased pace as the laps progressed. What happened? The track was cleaning up a bit more during that time. Ultimately, they served their role as a bracket to verify that the core test–245 versus 275–was valid, as we demonstrated similar ultimate pace.

By contrast, our fresh, full-tread 245s and 275s could only do two flyers before slowing a bit. Their taller tread blocks simply generated more heat–a significant factor on this hot, early summer day.

The big takeaway, of course, was to put a pace increase value on the inch of extra tread width by upsizing from 245 to 275. And that number was a solid six-tenths. Data logs show the increase came via two avenues: higher mid-corner speed in several sweepers and earlier corner exit throttle-up down each straight.

The data show where the 275mm Nankangs (red trace) hold the advantage over the 245mm Nankangs: in the turns. 

Fitting wider wheels and tires can be quite the challenge, especially when the sizing gets to be this big. Fenders need massaging, steering may need to be restricted and spacers have to be dialed in. It can be a lot of work. Is it worth it? Now you have the data–and the prices–to help you decide.