Bias ply slicks or radials: it’s the back-and-forth topic that quite honestly hasn’t existed in drag racing long enough to be called an age-old debate, but it’s one that the sport is quietly answering all on its own. Sure, there are applications in the sport — fuel cars, for example — where we’re unlikely to ever see radial tire construction implemented, but from heads-up doorslammers to bracket cars, radials are becoming less the minority and more the norm. So convinced of the advantages that a radial provides, the team at Mickey Thompson developed and launched several new tires to the market last fall, and among them were radial slicks in tread widths and diameters meant specifically for heads-up drag racing — namely Outlaw 10.5, Outlaw Drag Radial, and Outlaw 8.5.
The tire that’s been through its paces to the greatest extent to this point is the new Outlaw 8.5-specific rubber — the 26 x 8.5R15 3052R — and today, we’re going to take a closer look at the tire and how it compares in design and performance to the bias ply 8.5-inch slick with the help of Mickey Thompson’s Tom Kundrik and West Coast Outlaw 8.5 standout Anthony Smith.
Under The Surface
Most drag racers are familiar with the makeup of a bias ply slick tire, in which the plies are oriented in a criss-cross pattern at 30 to 45-degree angles from bead to bead across the tire. Both the tread and the sidewalls share the same ply cord makeup, and as such, this gives drag racing slicks their ability to flex. This is illustrated in the wrinkling and squatting of the sidewall that helps plant the power to the ground at the hit. Such flex causes varying ranges of deformity of the contact patch during launch and at speed. This, of course, isn’t a bad thing, but caters to certain applications and track conditions.
A radial tire, meanwhile, has plies in the sidewall and the tread that are largely independent of one another. Radials typically feature plies that run perpendicular across the tire, stretching from bead to bead, giving the sidewall its strength. Another set of plies, made of braided steel, then run longitudinal to the tread surface around the entire circumference of the tire. This design gives them a more consistent contact patch and less overall rolling resistance. They also lack the “shock” that a bias ply tire endures on launch, at shift points, and over bumps in the racing surface.
“A radial is definitely more effective than a bias ply, and a lot of the track prep is going the way of the radial,” says Kundrik. “A radial is general five to eight numbers quicker and at least one to two miles per hour faster, and so we wanted to take advantage of that.”
A radial is general five to eight numbers quicker and at least one to two miles per hour faster, and so we wanted to take advantage of that. – Tom Kundrik
You see, the early drag radials were designed as road-going tires with some performance characteristics on the track. For that reason, the tires had treads to make them drivable on the street. And although said tread patterns have become increasingly minimal in recent years, they’ve still been present. But today, Mickey Thompson is taking more the approach of developing radials specifically for the street and strip, and then going all out with race-specific radials for the drag racing market. And as such, these new race tires are void of any tread patterns — they are, for all intents and purposes, a radial slick. The 3052R is as smooth as a baby’s butt, and the larger 3062R looks just like a 29 x 10.5 slick. By doing away with the treads, Mickey Thompson is maximizing the contact patch of the tire, which helps it perform just that much better.
These are purebred race tires, and they’re ushering in a new level of performance unlike anything their ancestors were capable of.
As Kundrik shares with us, the engineering team at Mickey Thompson took what they learned from their highly regarded 275 Radial Pro tire launched in 2013 to make these new tires more forgiving on tracks that aren’t as well-prepped. In doing so, the 3052R can better recover from greater wheel speed than a radial might have traditionally.
“That’s the biggest thing in a radial, is making it forgiving. A radial doesn’t absorb power. The good thing about a radial is that it doesn’t absorb power, and the bad thing about it is that it doesn’t absorb power,” Kundrik says with a laugh. “The reason a bias ply is slower is because it does absorb the power, but that makes it more forgiving eating that horsepower up.”
The 3052R uses the same R1 compound as the 275 Pro tire, and measures a 9.9-inch section width, 8.5-inch tread width, an overall diameter of 26.4-inches, and 83-inches in circumference.
In Practice: The 3052R Outlaw 8.5 Tire
Ask any drag racer that’s run both a radial and a bias ply their opinion and you’ll likely get the same range of responses. In general, a bias ply is more forgiving off the starting line, particularly on hot or less-than-stellar surfaces, and with its sidewall characteristics, is typically quicker to sixty-feet. The radial, meanwhile, takes more finesse at the initial hit, but makes up for it with a smoother ride and additional speed thanks to the stiffness and improved rolling resistance.
It’s perhaps that initial hit that really makes the difference, as bias ply tires can spin and re-hook, while radials are known to spin and then just continue to spin. But put a radial on a well-prepped racing surface — the “flypaper” type of track, as it’s become known — and a radial is hard to beat.
Anthony Smith echoed these same findings following his early experiences with the 3052R after running an 8.5-inch slick for a number of years previously. Smith, one of the frontrunners in the West Coast 8.5 tire arena, runs a turbocharged small block in his Ford Mustang that cranks out more then enough power to put an 8.5-inch tire up in smoke.
“In moving to the radial, we definitely knew that we were going to have to make some suspension changes,” says Smith. “There was the wheel speed issue as well, because you need to keep it up with the slick and tame it down a little with the radial.”
In moving to the radial, we definitely knew that we were going to have to make some suspension changes. There was the wheel speed issue, as well, because you need to keep it up with the slick and tame it down a little with the radial. – Anthony Smith
Despite each of the four events he’s run the 3052R at occurring on a hot and greasy race track, Smith has already displayed the potential of the radial, knocking several hundredths off his personal best and gaining some two miles per hour at the stripe. Smith’s quickest previous sixty-foot was a 1.23, while his best thus far on the radial is a 1.28 — indicative of the progressive implementation of power needed for the radials.
Says Smith, “I was really bummed that we had to give up so much in sixty feet, but we really made up for it on the top end…like major made it up. Now, pouring the power in at the sixty-foot mark, the tire is much more forgiving and the car responds to it much better than with the bias ply. We’d often be hazing or blowing the tires off at that point, but the radial just takes it and goes.”
The ET Drag Radial
The ET Drag Radial line is currently composed of nine different tires, with the 26 x 8.5 3052R serving as the “baby” of the bunch. The range goes all the way up to a 33 x 14.5R15, and includes a 29 x 10.5 tire that should be popular with heads-up racers. All of the tires feature Mickey Thompson’s R1 compound, which has set all kinds of records in the 275 Radial Pro tire.
The forgiveness of the tire and the performance downtrack, for Smith, has parlayed into a new best of 5.11-seconds at 147 mph — nearly a tenth quicker and four miles per hour faster than his 5.20 at 143 mph on the bias ply slicks.
Overall, Kundrik reports the same kind of gains for others in the class. During a test session in Florida, Ultra Street racer Bill Gregan tested a 275 ET Street Radial and the 3052R back-to-back and gained a full tenth, jumping from a 5.21 to a 5.11. Overall, the previous best for the Outlaw 8.5 class of a low 5.0 on the 3052 bias ply has jumped considerably to a high 4.80 on the 3052R.
We also bolted the 3052R tire on our supercharged, street legal 1965 Mustang, with which we’ve been entering NMCA WEST events this season in order to gain points before debuting our new more class-specific Project Evil 8.5 Mustang later this year. The Mustang, a nine-second car that’s certainly down on power for the class, responded well to the tires, with 1.42 sixty-foot times and solid handling downtrack. Once Evil 8.5 is on course and we have more suitable horsepower, we’ll have a much better grasp of how the new Radials perform.
Having read this, you might be wondering if, at least in some categories, this new wave of radials will render bias ply slicks obsolete. And as we’ve seen, that’s not necessarily the case. A number of radial tire racers have switched to bias ply tires on hot race tracks not prepped specific to radials in the past, and even Smith shares that’s likely to switch to the bias ply during the hot summer months on marginal race tracks, but will undoubtedly move back to the radial when the track and the conditions merit putting some serious numbers down.
At the end of the day, it’s all about matching the tire to the conditions and the combination, and a place remains in drag racing for both radials and bias ply tires. What Mickey Thompson has done with their new Drag Radials, however, is develop a tire that brings together the best of both worlds as well as the technology that’s available today will allow, and the result and is ever-greater performance on the race track in the never-ending battle for elapsed time, speed, and win lights.