Over the last three years, the engineering and development team at Mickey Thompson Performance Tires & Wheels has been working overtime to churn out some products that have revolutionized the sport of drag racing, and in the small tire doorslammer arena, in particular.
First, they rolled out the new one-piece Pro-5 ET Drag Wheel, and the earlier this year, the wraps were pulled off of their first new radial tire design in nearly a decade, known as the ET Street Radial Pro. The new tire was designed to be a game-changer, and there’s little doubt that it’s been exactly that.
While Mickey Thompson was putting the finishing touches on the Street Radial Pro tire behind closed doors, the Power Automedia crew was hard at work on our Project BlownZ Chevrolet Camaro 275 Drag Radial entry. At the heart of it all was the ground-up build of the 388 cubic inch LSX powerplant that, combined with the boost delivered by our ProCharger F-1R supercharger, would unquestionably put us over the 1,000 rwhp mark. That’s plenty of power to get our feet wet in the NMCA WEST and PSCA venues, and maybe…just maybe…go some rounds.
With that kind of power on tap, however, the golden rule of drag racing is that your car is only as good as the rings of rubber that it’s rolling on. So when Mickey Thompson rolled out their new rubber, our choice of shoes was a pretty easy one. Along with a set of the 275 ET Street Radial Pro’s, we also picked up a set of M/T’s Pro-5 wheels to wrap the record-setting new tires in.
In this tech review, we’ll take a closer look at both the Pro-5 wheels and the new Street Radial Pro tires and, along with M/T’s new Motorsports Manager Tom Kundrik, share with you how both of these products have re-shaped the industry and the record books.
The Pro-5 ET Drag Wheel
When Mickey Thompson launched the Pro-5 ET Drag Wheel lineup three years ago, it featured a true one-piece bead-lock drag racing wheel that, thanks to its machined construction, has virtually zero run-out. For the uninitiated, wheel run-out is the measured difference in the axial (side to side) and radial (up and down) measurement of the wheel, typically calculated at the bead seat on both sides of the wheel.
According to M/T, two and three-piece wheels assembled with a pair of shells always have some some degree of run-out due to tolerances in the machines that form and weld the wheels, but rest assured that manufacturers keep a tight lid on quality control if run-out falls outside their minimum specification.
Our goal was to create the lightest, truest, straightest wheel on the market. It was the first one-piece integrated bead-lock wheel. We designed it and said, ‘here it is, no one has ever done this.’ — Tom Kundrik
Now, there’s nothing wrong with some run-out, after all, racers have been utilizing two and three-piece wheels for decades and continue to do so today, but M/T claims the fully-machined, one-piece design creates what is essentially as “true” a wheel as you can produce, and that’s exactly what Mickey Thompson wanted to bring to the table.
According to Kundrik, weld-together bead-lock wheels generally have a run-out of around .020″ to .030″. The Pro-5, on the other hand, measures between zero and .001″.
As a fully-forged, fully-machined, one-piece wheel, there are no welds to be found inside the “bell” of the wheel. They are, in every sense of the word, one-piece. And that means other advantages, namely that they’re incredibly light and provide exemplary strength. Said Kundrik, “Our goal was to create the lightest, truest, straightest wheel on the market. It was the first one-piece integrated bead-lock wheel. We designed it and said, ‘here it is, no one has ever done this,’ and it’s worked out really well.”
“Other manufacturers have since come out with a one-piece bead-lock, but this one was the first, and it really revolutionized the bead-lock wheel world, explains Kundrik” Mickey Thompson produces the Pro-5 fronts in a 15″ x 3-1/2″ size, with varying rear spacing and bolt circle layouts. For the rear, the offerings include 15″ x 8″, 15″ x 12″, 15″ x 14″, 15″ x 15″, 16″ x16″, and the 16″ x 16″ with double bead-locks, meaning you can find a wheel for virtually any tire from a small 8.5 slick or 275 radial on up to a Pro Stock tire on a set.
On our Project BlownZ Camaro, we needed a 15″ x 12″ wheel to fit the 275 radials that we intended to run, and so we turned to the folks at Mac-Fab, who turned out an excellent bead-lock conversion on the one-piece Pro-5 wheel. We’ll be speaking more on the Mac-Fab conversion process in a future tech review.
The Bar Gets Raised
A decade ago, Mickey Thompson launched the ET Street Radial tire, and unbeknownst to the staff at the time, it would extend beyond its designed role as a street/strip tire and play a large part in the transformation of the sport of drag racing. That tire, imagined as the perfect blend of a road tire with drag racing attributes, helped to both create and grow an entire segment of the sport that today is bursting at the seams with racer participation and fan base. Perhaps most interestingly, however, is the fact that this tire that was originally designed for nine and ten-second street cars has managed to propel 3,000-plus pound doorslammers to elapsed times in the 6.50’s at almost 240 mph. And it’s remained essentially unchanged through the years.
What Makes A Radial A Radial
While the tread surface is the most obvious part of a radial race tire, it’s not what makes a radial tire a radial tire. Rather, it’s the cord plies that are arranged at a 90-degree angle to the direction of travel in the structure of the tire from the center of the tire. The radial cords in the sidewall allow the tire to act like a spring, giving it a degree of flexibility, while rigid belts reinforce the tread region for improved performance. (Image credit: Wikipedia)
As the racing tire industry progressed and pushed the boundaries of radial tire design and technology, Mickey Thompson knew that it was time for an encore, and they set out to create the next generation of high performance tires — this time with several thousand horsepower and previously unimaginable speeds factored into the equation. The result is the ET Street Radial Pro, which was tested last winter and officially unveiled to the world earlier this year.
“We wanted to take our market back,” explained Kundrik. “There were newer tires on the market that featured more forgiving designs, and we were still using a tire that was designed ten years ago. When we came out with our new tires, we knew that the compound would work, but we went in and changed the construction of the tire and gained our market share back. This is our world, you know. The outlaw, small tire stuff is what we do best.”
The ET Street Radial Pro differs from its ancestor in that it exhibits a more forgiving sidewall construction that has more flex like that of a slick. “It’s like a hybrid, you could say, in that it really blends the aspects of a radial tire and a slick, but it’s definitely still a radial tire,” said Kundrik. “What makes a radial tire a radial tire is just the way the play is laid, and so we haven’t exactly pushed the envelope of what a radial tire is, because it’s still a radial in every way.”
Because of the change in the sidewall construction, the new tire has changed how the car and the tire reacts to the racing surface. The Street Radial Pro allows for more wheel speed off the starting line, whereas the old tire was more of a dead-hook tire. Tracks had to be stellar for the old radial to shine, but the new tire allows racers to get down tracks that are “mediocre at best,” in Kundrik’s words.
This is our world, you know. The outlaw, small tire stuff is what we do best. — Tom Kundrik
While the compound remains the same, the differences are in the construction and in the tread, where there are fewer slots and grooves compared to the old tire. Before it’s debut, Mickey Thompson engineers knew they already had a winner on their hands, and the numbers put a tangible exclamation on it.
“We tested at three different tracks: Bradenton, South Georgia, and at Milan. We worked with different cars, the same cars, different power adders, all at varying venues in varying conditions. We put “Brand X” tires on some cars and they spun; then we put the Street Radial Pro on the same car and had sixty-foots as quick as 1.10.”
Here at Power Automedia, we ran the original ET Street Radial (275/60/15) on Project BlownZ for some early test hits before switching to the new Street Radial Pro. Because we’re still very much in test mode in every aspect of the car, from the engine and drivetrain to the chassis and down to the tire pressure, our results aren’t on par with the 275 radial category on the whole just yet. We have however, recorded a best sixty-foot of 1.29, and the Street Radial Pro has consistently gotten the car off the starting line without spinning, regardless of the conditions. Throughout our testing, our tire pressure has only varied from 17 to 17-3/4 pounds as we made adjustments pass-by-pass.
For those in the Outlaw Drag Radial ranks or classes where a larger 315 radial can be used, Mickey Thompson hasn’t forgotten about you. From the outset, the company’s plan has been to redesign both the 275/60/15 and the 315/60/15 and place them under the ET Street Radial Pro banner, and just as the 275 has taken the sport by storm, so too will the larger tire when it’s released in the near future. For now, we and the rest of the 275 Drag Radial racing world will enjoy the fruits of the competitive spirit that embodies the racing industry that’s delivered this revolutionary next generation of racing tires and wheels.