We know what you're thinking: Those namby-pamby street tires are for weenies, and the DOT race tires work way better on the street, right? Wrong. While you're struggling with a stone-cold Supersport toss-off that's rock hard from too many heat cycles, your buddies on their high-performance street tires will be long gone.
Race tires are specifically meant to do one thing: Stick like glue, for one heat cycle. To that end, they are designed with an entirely different philosophy from street tires, and those differences make them unsuitable for street use. One obvious difference is most race tires have fewer grooves for more grip. And while this is great on a dry road, riding in the rain can get pretty hairy. But this is just what you can see, and it's perhaps more important to know what's going on inside the tire to fully understand the differences.
Max Martin, with Avon Tyres, says its Azaro Supersport bun is designed with a high arch and very high crown, particularly the front tire. This makes a race bike steer quickly (at the expense of stability), and gives more surface area on the side of the tire for more traction at full lean. The Azaro Sport street tire has a rounded profile, which puts more tread on the road when the bike is straight up for better wear, as well as being more stable and allowing easier line changes in midcorner. Put the race tire on the street and it will wear quicker due to the pointy profile.
Martin also pointed out differences in casing design, with the Supersport tire having an additional ply and tighter winding for higher cornering loads. However, on larger bumps found on public roads, this extra rigidity will have the race tire chattering earlier than would the softer and more compliant street tire.
Sport Tire Services' Dennis Smith points out that the Dunlop D207 Sportmax is designed to work correctly at the reduced temperatures found on the street, as opposed to the higher temperatures found on the racetrack. And that you'd almost never be able to generate track temperatures during a street ride to take advantage of the extra grip offered from a race tire. Smith also mentioned the material and production costs are totally different for each type, with the race tires costing significantly more than the street tires.
According to Mike Manning of Dunlop Tires, the D207GPs utilize a "cut breaker construction," in which the plies are overlapped to give good side grip. Compare that with the D207 Sportmax, which has a "jointless belt construction," giving more stability and a smoother ride. Manning also added that a street tire's rubber compound is designed to go through more heat cycles, as well as having silica added to give better wet grip.
So let's see, a street tire will generally have better wear, more stability and superior wet-weather performance compared with a race tire, offer similar grip (and most likely more) at real-world tire temperatures, and give constant performance over many heat cycles-all for less money. Sign us up.