Go small or go home. It sounds weird, but that’s the trend in the plethora of small-tire racing classes popping up all over the place. As horsepower levels continue to climb, sanctioning bodies are making things interesting by continuing to decrease tire size, whether the mandate is a 10.5-inch slick, a 275mm-wide drag radial, or an 8.5-inch slick. Incredibly, no one’s complaining about a lack of hook either, as drag racers are now running 6-second e.t.’s on 275mm radials. That’s in the quarter-mile, folks, not the eighth-mile! Leading the charge is Mickey Thompson Performance, one of the most legendary brands in all of motorsports. The company’s recently launched ET Street Radial Pro tires have decimated the performance barriers once associated with radials. Although blazingly fast radial cars are certainly making a lot of noise, Mickey Thompson’s vast array of bias-ply slicks are still getting the job done at dragstrips around the world. In order to catch up on the latest in tire technology, we had a long chat with Ken Warner of Mickey Thompson, covering topics ranging from air pressure to tire compounds, to burnout procedures, to tubes, to tire temperature, and everything in between.
Revolutionary RadialsMickey Thompson revolutionized drag radial technology over a decade ago with the introduction of its ET Street Radials, giving rise to a new wave of racing classes based on its popular 275mm-wide tire. The company recently improved upon the original to create the ET Street Radial Pro, and the results have been staggering. Many racers report that their cars run faster on the new 275mm ET Street Radial Pros than the older 315mm ET Street Radials. Likewise, racers are now ripping 6-second quarter-mile passes on these hot new radials. You read that right. Racers are now running 6s on radials, and making it look easy. So what improvements have been made that account for such a vast performance improvement “There are several factors at play, one being reduced void, which puts more rubber on the ground,” says Ken. “Most importantly, the construction of the tire has changed. Through extensive R&D and testing, we’ve been able to tune the carcass of the tire to absorb less power during the launch and throughout the run, this allows the tire to maintain its uniformity, stay planted, and roll with less resistance. If the tire absorbed more power it would distort and lose its uniformity.”
Radials or Slicks?With all the hype surrounding drag radials these days, casual enthusiasts might wonder why anyone would want to continue running bias-ply slicks. Even so, traditional bias-ply slicks are still the overwhelming drag tires of choice for the majority of racers for several reasons. “Bias-ply slicks and tires such as the ET Street definitely have a purpose. Cars utilizing manual-shift transmissions, in most cases, still use these types of tires due to their increased footprint and power absorbing carcass,” Ken explains. “Bias-ply tires are far more forgiving during launch, and thanks to their longer footprint, a clutch car can dump the clutch and have the tire spin in a more controlled manner. With a radial tire’s smaller footprint, there’s a greater chance of blowing off the tires. In many cases, bias-ply tires are the choice of many racers that have automatic and manual transmission race cars. They offer the benefit of consistency and reliability. Bias-ply tires can bridge the gap in cases where a race car doesn’t have the suspension to make consistent runs with radials or when simply index racing, where bias-ply tires are very consistent.”
Suspension TuningDrag radial racing classes are exploding in popularity, but since radials require different suspension tuning, many racers are in for a rude awakening when switching from slicks to radials. According to Ken, with radials the engine and suspension must be tuned in tandem to optimize traction. “The suspension must be set up in conjunction with the application of power. Unlike with slicks, you can’t just dump the clutch or leave the line at an enormous rpm,” says Ken. “Instead, the launch and how quickly the power is ramped in throughout the run have to be dialed in along with the suspension. Radials are far less forgiving, so you really have to plant the tire hard and keep it that way.”
Radial OptionsMickey Thompson has been in the drag radial game for so long that its catalog of radial offerings has grown to encompass several different types of usage. The original ET Street Radials are perfect for heads-up racing classes that require DOT-approved tires. As long as road conditions are dry, they can be driven on the street as well. Likewise, the ET Street Radial IIs have the same basic design, but are available in diameters up to 20 inches for late-model vehicles. In contrast, the ET Street Radial Pros are also DOT approved, but not intended for street use. Instead, they are tires purpose-built for 275mm radial classes and they feature a larger footprint and a revised carcass for enhanced grip. Last but not least, Mickey Thompson’s ET Drag Radials are a cross between a radial and a traditional slick, featuring radial construction with a grooveless tread surface. “The ET Drag Radials are outstanding performance tires. Their unique design makes them very popular in Competition Eliminator, Stock, and Super Stock classes,” says Ken.
“Designing tire compounds is tricky. Vehicle weight and transmission type play an important role in compounding, since they require different levels of controlled slip.” –Ken Warner