Mickey Thompson's Ken Warenr
Accelerating from a standstill to 330 mph in 4.6 seconds, it's a Funny Car's nitro-drinking 7,000 hp that seizes most of the glory. However, although it plays what is arguably an even greater role in achieving such scintillating performance, few give due props to modern tire technology. "Wow, those tires sure do hook!" isn't exactly a common utterance in the grandstands of an NHRA event. Nonetheless, tires are what ensures that that 7,000 hp translate into 5 g's off the starting line and 0.890-second 60-foot times. Why, yes, tires are very underrated.
Helping put the power down for pros and weekend warriors alike-since day one-is Mickey Thompson Tires. It's a company that needs no introduction. On any given weekend on any given dragstrip, chances are the vast majority of racers will be running Mickey Thompson drag tires. To help you get the most out of your drag tires, we solicited the expertise of M/T's Ken Warner. Even if you're a seasoned track veteran, Ken's got a bundle of tips that should shave a tenth or two off of your e.t.'s.
Hard vs. Soft
Since drag tires are significantly softer than street tires, racers often assume that softer is always better. This isn't always the case. Creating a tire compound is a very complex process. The goal is to provide the best possible performance relative to the intended use of the tire. "Softer-compound tires are preferable for lightweight vehicles, and harder-compound tires work best on heavier vehicles," explains Ken. "If the compound is too hard on a light vehicle, it may reduce traction and braking ability. If the compound is too soft on a heavy vehicle, it can cause premature wear in addition to performing poorly in regard to traction and braking."
"Drag tires are designed to either dead-hook or spin in a controlled fashion," Ken says. "You must compound the tire for its intended use. Drag cars have many different engine, transmission, and power-adder configurations. A high-horsepower car that utilizes a manual transmission requires a different type of compound than a high-horsepower car with an automatic transmission. When you dump the clutch with a manual transmission, a dead-hook will shake the tires or bog down the motor. A slight amount of controlled spin is preferable, where the right amount of wheel speed and traction allows the car to accelerate rapidly while going through the gear changes. On the other hand, since automatics have torque converters and the launch is not as violent, a dead-hook usually works best. All these factors have to be considered when designing a tire."
Not only have racers run quicker times with ET Street Radials than with ET Streets, M/T also openly admits that this is the case. So did the company shoot itself in the foot? Not exactly. While M/T's drag radials are proven performers, Ken says they are far less forgiving than standard bias-ply slicks. "Due to a drag radial's stiffer construction, they are not as reliable in regard to traction and recovery from spinning as a bias-ply tire," he explains. "Drag radials have the potential to be quicker, but can be very finicky, especially with a manual-transmission car. They generally require a much more time-consuming chassis setup."
Burnout lengths vary depending on the car and the track conditions, so some experimentation is necessary. However, there are some basic guidelines beginners can benefit from. M/T recommends spinning the tires until you see smoke billowing over the rear bumper in the rearview mirror. "Drive the car hard out of the burnout box and prestage immediately," says Ken. "In a very light car or a dragster, you will feel the tires bog you down during the burnout when it's been long enough. Again, prestage immediately, as this will glue you to the track." When the ambient temperature is hot, the burnout can be shortened to about half to two-thirds the normal length.
Mixing Slicks And Radials
For those who don't want to invest in a set of skinnies, it's common practice to run regular street tires up front when bolting up slicks at the dragstrip. This can make a car twitchy, but as long as you're smooth with the steering wheel you should be OK. "We recommend that bias-ply tires and radials not be mixed due to poor tracking," says Ken. "However, it is fairly uncommon in drag racing to have adverse handling issues due to mixing radials up front and bias-ply slicks out back. Drag racing is not considered a sustained duration of speed; therefore, it does not amplify the poor handling characteristics you would experience during normal street driving."
"The more air pressure the better," Ken says. "If the tire is right, the chassis is right, and everything is working properly, you want to run the most air pressure possible. More air equates to less rolling resistance, which yields better e.t.'s and trap speed. With too little air pressure, a car tends to drive the wheel into the ground at the starting line, which could pinch the tube and de-bead or cut the tire. Also, the car will handle very poorly by swaying around at the top end of the track. If you need assistance, you can always call M/T or check the tech section on our Web site for an air pressure staring point."
It's not uncommon for a tire to lose grip before its tread wears out. All tires and compounds will harden or cure when subjected to heat cycles. Fortunately, some simple techniques can greatly increase the effective lifespan of drag tires. "Overheating the tire will accelerate the effect of hardening, so it's important not to perform a longer burnout than necessary," explains Ken. "If you see any signs of graining on the tread, rotate the tires from side to side. This will reverse the direction of the tread tearing and smooth the tire back to a velvet texture rather than a rough texture."
Rim Screws & Bead locks
"Rim screws are required when there are signs of the tire slipping and turning on the wheel," Ken says. "To check for this, simply mark the tire and the wheel with a straight chalk line at the sidewall and the wheel lip, and monitor slippage after each pass. Many racers successfully run tubeless drag tires with rim screws. However, M/T recommends using racing tubes at all times when using screws. Rim screws are designed to pin the wheel lip to the bundle of bead wire embedded in the bead of the tire. On the other hand, bead locks are designed to clamp the bead for maximum bite to completely eliminate tire slippage. Bead locks are highly recommended for drag cars that run 200 mph or faster."
When it comes to tires, the Department of Transportation is the Federal watchdog that ensures your meats are safe to drive on the road. "Obtaining DOT approval involves passing indoor lab tests under high-speed and extended loading conditions," explains Ken. "The tire is also required to meet dimensional requirements and pass tests for bead unseating and puncture-penetration resistance. It should go without saying that non-DOT-approved tires should only be used at the racetrack."
The vastly different types of construction used in drag tires result in vastly different tire weights, but how much does that impact performance? "The weight of a drag-slick radial is very comparable to the weight of a bias-ply slick," says Ken. On the other hand, DOT radials (like M/T ET Street Radials) are heavier, but the radial construction has such low rolling resistance that the extra weight is hardly an issue. "Please understand that radials do not work on all race cars," Ken cautions. "They are very temperamental and require a lot of experimenting and chassis tuning."
"Mickey Thompson ET Drags are the ultimate 'strip tire, offering maximum traction and consistency," Ken says. "They are available in both bias-ply and radial construction. ET Street tires are DOT-approved versions of ET Drags best suited for racing classes that require DOT tires. ET Street Radials are intended for racing classes that require DOT-approved radial tires. Due to their incredible compounding and construction, ET Street Radials have been proven to be faster than bias-ply ET Streets, but they work best with automatic transmissions and require tuning the car to the tire."
One of the best things about buying a fresh set of slicks is that you get to break them in. While it's hardly rocket science, there is a right way to do it for maximum performance. "Mickey Thompson Tires suggests that you increase air pressure by 0.5 to 1 psi, then perform a generous burnout and drive the car hard out of the waterbox," suggests Ken. "This will help scuff the tires and secrete the tacky oils from the tread area."
Although the rule of thumb for tire growth is 1 to 1.5 inches at 150 mph, there are far too many variables to definitively predict how much tires will grow as a car traverses the track. "Drag tires are basically soft balloons with sticky rubber on them that hook the car up off the line and down the track," explains Ken. "Naturally, they elongate and grow in diameter." How much they grow depends on the car and tire choice. The taller and wider the tire the greater its degree of growth. The weight and speed of the vehicle factor into the growth of a tire as well. "It may take some trial and error to see how tire growth affects your gearing," Ken says.
M/T Drag Wheels
Both strength and light weight are critical properties of any quality drag wheel. Low mass reduces drivetrain losses and improves weight transfer, so Mickey Thompson decided to build its own line of forged-aluminum wheels to complement its tires. "Our ET Drag Wheels are the only rotary-forged wheels on the market," says Ken. "That means they are ultralight, very round, and extremely strong. When you carry the front end of a race car in a wheelstand for 60 feet, you can be confident that the wheels will not fail upon touchdown." M/T's wheels are available for skinnies and slicks, and each is drilled with a dual bolt pattern, allowing fitment for a multitude of applications.
When racing season comes to an end, drag slicks are usually thrown in the corner of the garage to collect dust until the spring. Unfortunately, this type of neglect can reduce tire life and compromise performance. During winter months, or whenever tires are being stored for long periods of time, Ken suggests removing them from the car or jacking the car off the ground to remove load. Drop the air pressure to 5 psi and keep the tires away from direct light. "It's best to keep them covered up and avoid exposing them to extremely high or low temperatures," he explains. "Also, keep tires away from electric motors, furnaces, and air compressors, since they create damaging heat."
Mickey Thompson Tires