Drag Radials’ Best Share Their Tricks Of The Trade
Whether it’s on a Mickey Thompson 275 or the larger 315 Drag Radial tire, many of the front running competitors in the Drag Radial arena tend to make their jobs look relatively easy. However, make no mistake about it; planting a set of these tires with upwards of a couple thousand horsepower – on stock-style suspension no less – is no leisurely walk in the park. And as each and every one of these racers will attest, there’s no such thing as simply bolting on a set of radials and going. Years of testing and refinement on a given combination go into the records and race wins achieved by these competitors, and even the best often struggle to get these race-bred DOT-approved meats down the racetrack.
The history of the drag radial is a tricky subject. Mickey Thompson and McCreary Rubber were arguably the innovators when it came to the first “versions” of super sticky street tires designed for straight line traction. However, it was BFGoodrich that really promoted the initial “Drag Radial tire” in the mid to late 1990s, followed by Nitto. The BFG was a good sticky tire with a fairly long shelf life, but it just wasn’t capable of handling the biggest 700+ rwhp street or all-out race cars. Mickey Thompson turned the drag racing world on it’s head with it’s version of the drag radial – a balls-out no compromise tire that could hook almost any race car. It was so good in fact that it got banned from several racing sanctions. But M/T would roll on, creating a huge buzz with the tire – to the point where today at least 40% of sanctioned street car event classes run almost exclusively on drag radials.
So what does it take exactly from a setup standpoint to consistently reel off the mind-boggling numbers that these racers put up? Well, we wondered that question too, and so we turned to four of the baddest racers in the business, representing both the 275 and 315 side of things, as well as Carl Robinson of Mickey Thompson tires to learn more about what goes into not only the setup, but the burnout and starting line procedures to make the radials hook.
David Wolfe and Kevin Fiscus are two of the toughest Outlaw Radial racers the sport has seen, and two of the quickest as evidenced by their epic seesaw battle in South Georgia this spring, where Fiscus ultimately walked away with the quickest eighth-mile Outlaw Drag Radial pass in history at 4.33 seconds. Wolfe, already known for breaking backs on slicks and as crew chief for legend “Big Daddy” Dwayne Gutridge, was a game-changer last season when he obliterated what everyone thought was possible on radials and dominated the Duck’s high stakes races in the process. He also set the quarter mile record last fall at an insane 6.57 seconds at 227 MPH on 315 radials. World record aside, Fiscus has several high-profile wins to his credit and is an odd-on favorite anywhere his big block, twin-turbo mount shows up.
On the smaller 275, there’s perhaps no one tougher than Maryland native Chris Evans, who last year captured not one, not two, but three track/series championships in the popular X275 division, while also setting the class standard at 4.91. Evans has also been 7.59 in the quarter mile in X275 trim in his supercharged, small block combination.
Also setting records on 275’s, there’s perhaps no radial-clad machine out there that does it with more finesse on a more consistent basis than Sean Lyon’s turbocharged ’93 Mustang. Lyon currently holds the NMRA record at a killer 7.53 seconds and if you want to beat him, you’ll have to flat outrun him, because the Panhandle Performance ride doesn’t struggle with traction very often.
And as a true authority on the subject, Carl Robinson at Mickey Thompson Tires – with more records, championships, and race wins than one could count to their credit with their industry-leading radials – also shares his thoughts on optimum tire pressures and the methodology of wheel selection.
A myriad of elements go into make a racecar hook, including suspension, weight distribution, power control, and launch procedures – all of which we’ll get into below – but none is easier to control than tire pressure. And because we’re discussing how to make radials hook, this is the logical starting point for our guide.
Radial tires, with their stiff sidewall design, naturally require more air pressure than their bias-play racing slick counterparts, and according to our experts, their tire pressures vary only slightly from one racing surface to the next.
Fiscus is typically at or around 14 pounds in the 315’s on his Mustang, with small variances based on air conditions. “Temperature is the biggest thing – the colder it gets outside, the lower air pressure we’ll go,’ explains Fiscus. “But you’d be surprised, as we’ve probably been within a quarter of a pound on every pass we’ve made this year.”
Likewise, Chris Evans indicates he rarely, if ever, adjusts the tire pressure on his Mustang, “Regardless of where I am, even if the track is greasy, we might change it half a pound. What’s funny is down at MIR, the track surface is so good that we actually raise the tire pressure.”
Wolfe, certainly an authority on the subject of radials based on his accolades, has done his share of experimenting with tire pressure on different race tracks. “I’ve been all over the map with tire pressures,” Wolfe exclaims. “I’ve been as high as 16 pounds and as low as 12, and it just doesn’t seem to make a giant difference. It’s not a deal-breaker either way, but we found that they seem to run the best at around 14 pounds.”
Drag radials, like any tire from those on your daily driver to a massive Top Fuel slick, have an operating range provided by the manufacturer, and as Mickey Thompson’s Carl Robinson explains, that range is going to be applied based on the conditions.
“You want to run as much as you can get away with, but that’s a very sweeping statement,” says Robinson. “What it comes down to is the temperature on the racetrack combined with the ambient temperature dictating what the tire should want. But, track conditions have to be factored to necessitate a change, and typically when the track temperature is over 130 degrees, you’re going to have to make more than just an air pressure change to get down the racetrack. But on average, there’s probably a three pound functional range, up or down, that you can use to your benefit. Anything beyond that range gets kind of questionable. You really have to test the car and find these limits and your range.”
This functional range, according to Robinson, is dependent upon a number of factors, including the amount of horsepower the car produces, the weight, and the weight distribution of the vehicle. For a top running Outlaw Drag Radial car making plenty of horsepower, this range will commonly fall between 14 and 17 pounds, whereas a lesser-powered car that range might be 15 to 18 pounds and 17 to 20 for a street car.
“It really depends on how much power you’re trying to apply,” Robinson explains. “And the less power, the more inflation you’ll need. Inflation is the direct correlation to spring rate, which is the direct correlation to how much power the tire can absorb before it no longer has traction capabilities. There’s a certain amount of horsepower that can be absorbed by the tire and sent back up the driveshaft to the converter; the power then comes back and the tire says ‘no.’ The power repeats the process, and the converter then multiplies it some more. So depending upon your range of performance, your range of inflation will vary therein.”
Moving to the front of the car, each of the racers that we spoke with explained that small changes are commonly made to the travel on the front shocks to control how the car reacts on the launch. As with any race car, hanging the hoops to transfer weight is ideal, but only to an extent if you truly want to go fast.
“The bullhorns and the front suspension are the two things we adjust to control the wheelstands and power wheelies,” explains Fiscus. “If we’re running 4.60 or slower and that’s all the track will hold, we really don’t have to worry about any of that. We can get as much travel as needed off the line to make it hook. It’s on the better tracks where we can go 50’s, 40’s and now 30’s that we tighten the front end up with almost no travel to keep the nose down, because it doesn’t need the travel on the initial hit.” Ideally, Fiscus says, the front tires would ride an inch off the ground for the first 60 feet and lightly set them down.
And as Lyon explained, the setup in the front of the car is very much dependent upon the launch RPM the car has been set up for based on the starting line surface. For his car, he told us, the compression and extension of the struts is tuned according to this variable, which can vary as much as 500 RPM from a good to a bad track. And this RPM curve, as others races relayed to us, is meant to control the traction within the first 10 to 15 feet of the track.
The rear suspension setups, which are critical in any racing application regardless of the tire, are very much dependent on the surface at the starting line, the other classes that have raced on it in regards to rubber, and willingness of promoters to prep said surface.
“We’ll generally make some shock adjustments, both in compression and extension, but again, we’re only plus or minus three or four clicks, so it’s not really a lot of adjustment there either,” explains Fiscus. A common misconception is that a well-prepped racing surface is one-size-fits-all, but on the contrary, radial tires require a different style of prep than a big tire slick, Outlaw 10.5, or True 10.5.
“Slick tire cars want wheel speed so they want the tires in a controlled spin, whereas a radial dead-hooks,” Fiscus continues. “So if you get to a track where they’re running a lot of slick tire cars, you’ve really got to work on shock adjustments to get the car to move. And a lot of it’s power management at that point, because you have to reduce the power to make sure the car dead hooks.”
Interestingly, the nature of the track surface will occasionally call for extra ballast to make for a smoother and quicker ride. Fiscus’ Mustang weighs in at the minimum without any ballast, but as Fiscus explains, “If the track surface is bumpy, we’ll add weight to the back half of the car to keep it planted over rough surfaces.”
Evans’ Mustang, which weights in nearly 200 pounds light without ballast, has weight distributed around the car. And despite the common thought process that ballast should be in the rear, about 70% of that ballast is right in the middle of Evans’ machine.
“Dwayne Gutridge, of all people taught, me that little trick a long time ago,” explains Evans. “He said ‘why do you have all that weight on the back of the car? You need to put it in the middle.’ When I first started running my car, it was inconsistent and kept doing wheelies, and I moved about 40 pounds forward behind the drivers seat and it was like a night and day difference.”
Lyon, a fellow 275 runner, suggests much the same, with placement of the ballast moving from the rear to the middle of the car, again depending upon your launch RPM. Placement of the weight based on that RPM variable will determine both wheelspin and wheelstands.
Common rear gears for supercharged, eighth mile cars such as Evans’ Mustang include 3.50 and 3.89’s, but he believes the sweet spot just might be a 3.70. “I haven’t been able to try one yet – I haven’t found someone’s that I can borrow to try, because I hate to buy it and be wrong,” Evans said jokingly.
Rear gear ratios, as you might expect, can be affected by the quality of the racetrack, and as Wolfe explains, the taller the gear (as in the numerically lower gear) is more forgiving on a bad track. “If you put a lot of gear in one, they get real twitchy. And that’s why we ran a quarter mile gear, because it was more forgiving on the whole on bad tracks. But ss long as you’ve got the power, you can pull any gear you put in it.”
With the tire size a fixed variable, racers have experimented over the years with different wheel sizes to find the sweet spot of tire performance, with different combinations in use by different racers.
Fiscus has used both 10-inch and 11-inch wheels before settling on his current 12-inch setup. “I haven’t seen a lot of difference between them, to tell you the truth. But, I think for the 315, you want to be in that 11 or 12 range. Some run a wheel even larger than that, but we’ve been 4.33, so I’m going to say that’s the best wheel size,” Fiscus explains with a laugh.
“A wide wheel is the way to go,” explains M/T’s Robinson. “The wider the better, actually. Drag Radials like to be what we call ‘held out’ or ‘held wide,’ I don’t know if there’s such a thing as overdoing it, but we have seen 315’s on 14-inch wide wheels, so it can be done. Does it make a difference between 12 and 14? That’s hard to determine right now, but they definitely like to be held out wide, due to the construction of the radial tire. The belts go across the tread rather than diagonally. It’s really the shape and the construction of the tire that dictates the wider wheel.”
Mickey Thompson Tires come with a suggested average wheel width, but as Robinson explains, that figure is always open to interpretation. “It’s going to vary by the car, the weight of the car, the horsepower, and other elements. On some, it won’t make a difference, but on the high-end cars, it seems to be make a difference when they go really wide.”
Burnout & Starting Line Procedures
So you’ve got your high dollar, high horsepower car all setup and prepared. You’ve dialed in the tire pressures, you’ve made your suspension, power control, and other adjustments. Now it’s make-or-break time, and the starting line procedures can certainly be just that. We’re talking of course about the burnout process and the starting line positioning.
Burnouts in these cars tend to be short, because lengthy Funny Car or Pro Modified-like affairs just aren’t necessary to adequately clean and warm the tires.
“I just do a certain amount of RPM in first gear and then second gear burnout, and hold it for a certain length of time”, said Wolfe. “We’ve done this long enough that we try to get the tires to a specific temperature.”
“We just do a short, quick burnout,” agrees Evans. “Just start in first gear, get it in high gear real quick, and let off of it. But Al Marlow, for example, bakes his clear across the starting line every pass, so it’s a difference in people and what they like to do.”
With all of the big block turbocharged, twin turbocharged, supercharged, and multi-stage nitrous-fed behemoth powerplants out there, suffice it to say that most racers in Drag Radial are making more horsepower and torque than the tires should be able to handle. But that’s that’s where the element of power management come into play, as tuners utilize modern tools such as progressive boost and nitrous controllers to gradually deliver the power to the ground.
X275 cars, at least in relation to their Outlaw Radial big brothers, are attempting to plant far less horsepower, and as Evans explains, the tools that he uses to finely tune that power are surprisingly limited.
“In my ignition box, the only thing that I touch is the gear retard. In between different tracks, I have one program that’s pretty aggressive, and at a slippery track, I might move it over 100 RPM’s and the graph over less than one degree down off of what I take out now,” said Evans.
Evans’ machine also forgoes the use of progressive controllers and other tricks, going “commando,” if you will, with seven pounds of boost on the brake and topping out at 23 pounds.
In the power management department, an endless number of variables can come into play, right down to the last nut and bolt – the different boost and nitrous controllers, different wastegates and how you place the wastegates on the headers, camshafts, engine sizes, heads, intakes, and the list goes on. But as Wolfe explains, there are two common elements that any radial car should have. “Every car should have boost controllers and g-meters, and you need to work each of those against one another. Watch the g-meter, and adjust the boost until the meter reads high and says up there.”
And as you’d expect, that power management loses its management once the coals are being poured to it. “Typically, if a radial car makes it 60 to 100 feet, it’s gone; if I get that far, I can ramp it in as fast as it can go,” explains Fiscus.
With all of the modern serviceable, bolt-together converters on the market and all of the tuneable variables inside, one might think converter adjustments would be near the top of the list, but that simply isn’t so for the racers we spoke with.
“I only have one converter,” says Evans. “It works really well and I don’t know what I could improve by changing to another one. We run it pretty tight though; I’d have to guess it’s around 5,800. But it’s just an old welded-up 9-inch converter, so I couldn’t make adjustments to it even if I wanted to.”
Wolfe, meanwhile, has his own thoughts on torque converters and their role in the control of the race car. “You can only go so far one way or the other with the converters. I’m a firm believer that the converter should match what the engine is capable of and not be limited only by what you know to do with your car. I don’t believe you should put a weak converter in there to get down the track. It works for some guys, but if the track isn’t very tight, it’s going to suck regardless; it’s all about power application at that point.”
As you may have picked up on while reading the ideas and the thoughts of these four great racers, there is no one-size-fits-all method for preparing a Drag Radial-clad machine for excellent, race-winning, record-setting results. Each combination is different, and each racer and each crew chief has their own methodology that floats their particular boat. Like anything else, it requires time, perseverance, money, and of course the knowledge gained from past experiences and failures to make these cars consistently quick and fast. But at the end of the day, it’s the race track, and not the intricate details of your race car, that is the deciding factor and the ultimate challenger.”If the track is bad, there’s nothing you can do to get down it other than slowing the car down,” explained David Wolfe. “There aren’t any tricks to get around it, it’s just the nature of the drag radial. They just don’t like crappy tracks.”