You are here
Home > LATEST STORIES > Extension Benefits—How Radial Tires Are Changing The Way We Race, 60 Feet At A Time

Extension Benefits—How Radial Tires Are Changing The Way We Race, 60 Feet At A Time


Written By Paul Huizenga

Photography by the FSC Staff

If you could grab a fan out of the stands from a National Muscle Car Association race 20 years ago and drop them into an event today, the future shock would come at them from a lot of different directions. They’d find cars in the spectator lot making power numbers that would shame half the heads-up cars they were used to seeing, and they would have to come to grips with stock-class cars knocking on the door of single digit quarter mile times. But what would surprise that fan from 1998 most might be the way Radial cars go down the track—drag cars are supposed to squat and stuff the back tires up into the fenders, not stand up and cover the first 330 with suspensions fully extended. They’d wonder what kind of witchcraft had turned the world upside down, and worse still, why it wasn’t just the Radial cars that were doing it, either…

Conventional Wisdom, Conventional Results

A bit of background on drag race tire technology helps to set the stage. For decades, the bias-ply slick was the only game in town, and when competition-spec drag radials began to enter the scene, racers who tried to translate what they knew about suspension setup and power application to the new radial tires met with a lot of frustration. The go-to strategy for a slick—compression built into the suspension geometry on the hit to manage wheel speed and get the controlled slip a bias-ply tire needed to remain stable—simply didn’t work with a radial.

“It’s ultimately not so much a question of overall traction as it is the design of the tire,” explains shock and suspension tuning guru Mark Menscer. “A bias-ply tire simply can’t be loaded in the same way a radial can be loaded. A radial has a very stiff sidewall—we joke about them and say they’re like the trailer tires on the hauler you use to get the car to the racetrack. They require a tremendous amount of mechanical grip to get them to stick to the racetrack in the first few feet of the run, and then you have to keep piling load into them so there’s just this exponential growth in load.”

“A slick tire is really just about the opposite of that,” Menscer continues. “You need to lessen the amount of traction as you add power, because the tire wants to stay round, but it has this big baggy, floppy sidewall that tries to get out of shape, and that’s where tire shake comes in.” Consistency and quickness with a bias-ply slick requires a nuanced approach that balances available traction from the race surface, the power application curve, and how the suspension loads the tires in order to avoid blowing off the tire at one end of the spectrum, and unrecoverable shake at the other.

The Learning Curve

Faced with a new kind of tire that had big potential benefits, but no established tuning history, racers did what racers do—they began to experiment. As Jamie Miller (Pictured at left), crew chief for both Pro Mod racer Michael Biehle and Drag Radial hot shoe DeWayne Mills, recalls, “Going back to when the original 315 came out and Radial Versus the World started getting so crazy, you had guys taking cars and swapping them over from 10.5 and putting a radial on them. We basically went in with the mindset of ‘Let’s put the tire on and see what happens.’ Well, you found out real quick that that tire didn’t have the grip like a standard 10.5 or a big tire slick, so we had to find out ways to increase bite in the car. And that’s when guys started to mess around with making the 4-links real short in these cars and making them extend, basically increasing the load on the tire.”

As for Menscer, he came into drag racing as a blank slate, with nothing to unlearn. “I was building circle track shocks for Late Model and Modified. Basically everything we did was roundey-round stuff,” he explains. “We had gotten to the point in our relationship where they had invited me to come along and go to a drag race up in Indianapolis and they had one shock tech working on the truck. He could build a shock, but he came out of sprint cars or something. So they are going around the pits and they come up on customers who need help, and I somehow get drafted into the situation of helping these guys with an Outlaw 10.5 car. Now I don’t know about drag racing, but I know weight transfer, and how to make traction, so I start telling these guys what to do and because I’m ‘the guy from AFCO’ these guys unknowingly have me calling the shots on their drag car. They had no idea that I didn’t know what in the world I was doing.”

Fortunately for those racers, and for Menscer, sometimes not having any preconceptions lets you see things from outside the box.

“It was like a Cinderella story, though—the guys went out there and it did a great 60 foot, ran a personal best, the guy comes back with a big smile on his face, and I was hooked. I didn’t know better,” he admits. “All they told me was ‘we need traction’ and I thought, ‘I know how to make traction.’ If I can get a 1600 D Hoosier to hook up on dirt, I can get this [stuff] to work. They put glue on the racetrack! How are you spinning the tires?”

Prep School

How that glue (traction compound, technically speaking, typically ‘cut’ with methanol to make it easier to apply and faster to dry), rubber, and rosin are applied to the track surface can make or break a run, and what radial racers want is very different from what those running bias-ply slicks have traditionally preferred.

“The guys who are trying to prep the tracks are having a much harder time now, because you have series like the NMCA and they’ve found a way to run both a big tire and a radial and get great results for both,” says Miller. “But it’s also required racers to change their programs around a little bit, because if a big tire guy sees a lot of glue being sprayed around, he’s going to be raising hell because it sticks the tire and it wants to shake really bad. Well, now these guys are forced to make changes to their car if they want to run NMRA/NMCA or other series where they are getting big tire and radial being run in the same race schedule, and the preferred track prep is so totally different.”

Any time radial and bias-ply cars are sharing the same track, the level of preparation has to be a compromised in order to let everyone get down quickly, and safely. That middle ground is also leading to more similarities in the way radial and slick car suspensions are being set up, and that’s no coincidence.

“With the radial stuff, we started with what we knew on slicks, and now it’s come full circle and we are starting to put that same technology back into our slick tire stuff,” says Miller. “Now, what I am starting to see, and this has helped on quite a few Pro Mods as well, is that same theory of separating the rear suspension to increase bite in the car. I’ve been bringing that more and more into my slick tire stuff. It’s not so aggressive as what we are running on the radial, but I am starting to find that there’s this trend where it increases the bite and I am able to apply more power.”

Menscer adds, “What I’ve concluded is that the tire companies have taken notice and are starting to construct slicks with stiffer sidewalls, so the tire itself will allow the customer to run the car itself with more traction in it. Now, for years, we’ve run slicks with tubes in them, which makes them stiffer and gives more available traction. So what it seems like is that someone has put pen to paper and realized that wheel speed is just wasted effort—it’s a necessary evil to keep the tire round and keep it from becoming deformed and going into shake, but ultimately that’s driveshaft RPM that’s not converted into g-meter. Anything you can possibly do to turn every revolution of that driveshaft into forward motion of the car is a plus.”

“I was just out with a [bias ply] customer car, and his car has been very difficult through the middle of the track to get it to be consistent,” Miller continues. “So I spent two days just swinging 4-links in the car and not changing the tuneup. Not trying to fix it with the keyboard—trying to fix it chassis-wise. And right out of the box, we tried some things that we’d do with the radial stuff, and it started going right down the racetrack. So there is definitely something to be learned in the big-tire world, bringing that technology back into slicks, which is pretty cool.”

Photo Courtesy of Brad Eglian

The December 2017 Dirty South No Prep series finals at Mississippi’s Hub City Dragway were disrupted by surreptitious “guerilla track prep” under the cover of darkness, and the track crew had to work to remove the traction compound before racing could resume. The incident goes to show how important the condition of the track is, and how upset racers become when it’s not what they expect or want.

No Substitute For Experience

With a better understanding of how both kinds of tires react to the track surface prep, the power application curve, and the dynamic load applied to the suspension, it can be tempting to chase a technological solution to the problem, but both Menscer and Miller emphasize that there is no shortcut; having the right parts on the car is only the start.

“Going back about a year, year and a half ago, I started working extensively with Mark Menscer, because you are taking the shock and you are doing the exact opposite of what you are doing with a big tire or turbo Pro Mod car where you are compressing it, and you are basically pulling the shock apart,” Miller explains. “What we found was that when you get real aggressive with the 4-link, which gives the tire a bunch of bite, the shock extends and eventually it tops out so you have no more travel left.”

“When that occurs, and you have a track that is really glued up and has a bunch of grip in it, the car wants to wheelie. If you are on a track that is somewhat marginal, the car wants to spin. It’s a locked suspension at that point. So Mark and I started developing a way, by putting internal springs in the shock, so that when the shock starts to pull apart it basically hits that spring and starts to ‘roll over’—that has changed the way we run these cars.”

“There’s other guys doing other things—they have CO2 pods that go into the springs and they go off the pods and it basically lowers the ride height of the car as it goes down the track. I don’t particularly like that setup as far as having a drastic change in ride height in the car as it’s going down the track, so that’s part of why we came up with that spring,” Miller opines. “There’s a bunch of different ways guys are trying to accomplish the same effect. That has drastically helped.”

Menscer adds, “At first it was crude—just make the car throw the rearend housing out of it like it was broken. So it was like, ‘Ok, we have traction, but now the car is flipping over backwards,’ so we had to figure out how to keep the nose on the ground.”

Taking Notes

Per Menscer, “What we are trying to do is create a recipe for ET, and that recipe includes the engine tuneup and power management curve, converter characteristics, and chassis tuneup. Over the course of, say 500 laps in the car, you end up building a logbook that lets you flip to a page, just like a Betty Crocker cookbook, that says on a 122 degree racetrack, with this relative humidity, our [stuff] should run 4.06 with this tuneup in it, so let’s put all that in there and go out and make a lap.”

Menscer stresses that the most valuable thing you can spend money on is more track time, saying, “The thing that customers always say to me is, ‘I have all the same stuff as DeWayne Mills has got, so I should be able to run three-seventies.’ And I tell them, ‘you will be able to run three-seventies in 250 laps.’” He recommends starting simple as well: “99 chances out of 100, if you are not already very experienced, less is more,” he advises. “You need to have the range of adjustment in your 4-link, and you need to have the range of adjustment in your shock absorbers. But most of my guys who are starting a program from scratch will get more immediate results out of a good double-adjustable shock package and a baseline 4-link setup than they’ll get out of all the other things you can buy.”

He’s also been somewhat outspoken on the high-tech-because-you-can route.

“I said this a while back in an article, and I guess I am kinda famous for it because I get called out on it all the time, but I stand by it—having a bunch of gadgets under the car is code language for ‘I don’t know what the hell is going on with this.’”

 The More Things Change, The More They Stay The Same

Although our time-traveling race fan from 1998 might be surprised at how far things have come in 20 years in terms of performance, technology, and ET, one thing would still be just as true as it’s ever been—no matter what tire you’re on, there’s a direct relationship between the sweat you invest and your level of success.

“When everything is said and done, the money is spent, and whatever, what makes the car faster is racing the car and making adjustments,” Menscer concludes. ”You have to go make laps on it as a package. The guys who consistently go fast, we’ve spent weeks with them at the racetrack testing. The guys who go out and are a one hit wonder, and then are inconsistent? They don’t put laps on their car. That is really all it boils down to.”

Mike Galimi
Mike Galimi is the Director of Content & Marketing at ProMedia Publishing and Events with nearly 20 years of experience in motorsport writing and photography.