Tire Comparison Test: What Rubber Should You Choose?
Tires are a major investment, and one that drivers need to make decisions about each time a set wears out. Choosing a replacement tire can be like picking an air filter because there are so many choices, and tire dealers sometimes sound an awful lot like used-car salesmen. The simplest solution is to buy the same tires your car came with, and that’s a good option—after all, the engineers designed the suspension to match the OEM rubber. But what if you want, say, more cornering grip or would like to save a few bucks? What do you get if you upgrade to larger diameter wheels? Now what? To illustrate the possibilities, we tested different types of tires—high-performance, low-rolling-resistance and the cheapest set we could find—against a baseline all-season. We also sampled a high-performance tire on 18-inch wheels, 2 inches larger than our test car’s original units. Since tires massively contribute to how a car feels behind the wheel, we supplemented our instrumented tests with subjective analysis of all of the tires’ behavior both on the track and on a variety of road surfaces.
Michelin MXM4 205/55R-16
The MXM4 is new this year and thus has the latest technology. That’s likely why it posted the best lateral dry grip, a result we didn’t expect. In other tests, the tire was competent—typical for this genre. And don’t believe the “all-season” name—they’re okay in light snow, but you’ll need snow tires for serious powder. On the plus side, these tires rode quietly and offered the smoothest ride of the group. With good overall grip and predictable handling at the edge of the handling envelope—wet or dry—this class of tire would be the right choice for most people most of the time.
Michelin Pilot Sport AS+ 205/55R16
Stepping up the performance ladder a notch or two lands at a tire like the Pilot Sport AS Plus. It’s meant for drivers of high-end sports cars who want extra precision and grip, but not at the expense of bad-weather traction or reasonable wear. On the small test course, the tire outperformed the all-season in nearly every category and simply felt sharper. So it was more fun to drive. There are even higher-performing street tires—like the Pilot Sport PS2—but they’re more expensive and wear out sooner, especially if you frequently explore the outer limits of the tire’s performance envelope.
Michelin Pilot Sport AS+ 225/45R18
A common upgrade on today’s cars is to boost the diameter of the rim a couple of inches, add about half of that to the tread width and then reduce the sidewall profile enough to make the overall diameter the same. That’s called a plus-two fitment. In theory, you get more grip from the extra rubber, as well as that all-important aura of style. In reality, sometimes this works. A lower profile, wider tire realizes all its benefits only in conjunction with upgraded suspension that can keep the extra rubber flat on the road. And that’s exactly what we found on our plus-two Pilot Sports. It posted good numbers, but in aggregate it didn’t outperform its smaller sibling. If we had tuned the suspension on the Bimmer to keep the tires more square to the pavement, no doubt the raw cornering numbers would have been better. Bottom line: Be sure your suspension and driving skills are up to cashing the checks that upsize tires and wheels can write.
Bridgestone Ecopia 205/55R16
The Ecopia EP100 advertises lower rolling resistance, which increases fuel economy slightly. The compromise is reduced grip through the entire testing regime. These low-rolling-resistance tires are intended to stretch a gallon of gas as much as 5 percent, saving you money. It’s achieved by using different construction internally and a new class of rubber compounds with less internal friction. We didn’t have the opportunity to test for fuel economy, but Tire Rack has done so in the past, and it documented a 4 percent improvement on a Prius, over and above the Prius’s already low-rolling-resistance OEM tires. This all comes at the price of something, and that’s grip—these tires needed about a half-car length more distance to stop, potentially the difference between spilling your coffee and rear-ending the guy in front.
Republic Enterprise 205/55R16
We walked into a tire store and demanded the cheapest tire they could get in our size. In all fairness, the counterman tried to up-sell us to a Kumho tire that was only about $25 more expensive. For that hundred bucks extra, we should have listened. Bottom line: We’d rather buy used tires, if we were that desperate. Sure, the numbers weren’t terrible, but the lack of precision could make a sketchy evasive maneuver difficult for drivers of average skill.
We used Tire Rack’s test facility in South Bend, Ind., which has an instrumented track with sprinklers—perfect for wet and dry tests. The company’s own test results can be viewed at tirerack.com.
Testing tires is a tricky business because there are so many variables. We measured braking, lateral grip and an autocross-type lap time in both wet and dry conditions. To minimize the effect of changing weather conditions and, ahem, driver error, we ran each test several times over the course of one day. For the braking tests, we drove a half-dozen max-effort full-ABS stops and averaged the results. Then we did a half-dozen pairs of timed laps around the handling track, discarding any laps with missed gates or clipped pylons. Once we had a half-dozen good sets, we discarded the best and worst laps and averaged the rest. Skidpad g’s were calculated from times through a constant-radius section of the handling course, with similar refinement of the raw data. The next morning, we drove a 6-mile street loop on all five sets of tires. The loop had plenty of pavement variation, from smooth asphalt to coarse concrete, potholes and patched and tar-stripped concrete freeway blocks. This evaluation was completely subjective.
Bottom line: The raw lap times and skidpad lateral g’s tell only part of the story. Far more important is the subjective feel of a tire, as well as other tangibles like noise, road harshness and, of course, price.