Hoosier A6 and R6 Dry Racetrack & Autocross Only tires have proven themselves to be at the pinnacle of racing performance, but many autocross drivers don't know which one best suits their needs. There are some overlapping qualities between the two, however these tires are purpose-built for two different functions.
Hoosier A6 tires are intended to be used as autocross tires. The science behind this function is the very soft rubber compound. The tire has a lower operating temperature for maximum traction. Many autocross events are too short of a course to get a typical race tire up to its optimal race temperature, therefore if the tire is too cold you'll never get the best grip the tire can offer. A downside is that the treadlife is lower on the A6 when compared to the R6. However, if you want the quickest lap times at the autocross course, the A6 is definitely the tire that can deliver.
R6 tires are designed for drivers who compete in road racing where there's longer road courses or lapping days over a longer period of time than an autocross event. R6 tires use a harder rubber compound which takes more time to build up heat to reach its optimal operating temperature. Harder rubber compound also offers a longer treadlife.
The Hoosier R6 is also seen on many autocross courses and is still appropriate for use at these events. Many racers like this tire for autocross because they'll get much more racing time on their tire. However, if these tires are raced cold, racers will be sacrificing maximum grip for treadlife. It's recommended to run these tires hotter for autocross than the Hoosier A6 to maintain better traction.
Both tires will benefit from the Tire Rack Heat Cycling Service and it can be added to your order for $15 per tire.