Drag radial street-legal tires had their origin in racing. Originally, race cars used “racing slicks”- a type of tire with a smooth tread. The first production "slicks” were developed by M&H Tires in the early 1950s for use in contact patch to the track and maximized traction for any given tire dimension. Slicks were also used on road and oval track racing where steering and braking require maximum traction from each wheel.
Slicks, however, are not suitable for use on street cars which must be able to operate in all weather conditions. They are used in auto racing where competitors can choose different tires based on the weather conditions and can often change them during a race. Wet roads severely diminish the traction because of aquaplaning due to water drag racing. By eliminating any grooves cut into the tread, the rear tires provided the largest possible trapped between the tire contact area and the road surface. Conversely, grooved tires are designed to remove water from the contact area through the grooves, thereby maintaining traction even in wet conditions.
Since there is no tread pattern, slick tire tread does not deform much under load. The reduced deformation allows the tire to be constructed of softer compounds without excessive overheating and blistering. Modern day slicks have now developed particular performance qualities in a specific window of temperatures, becoming "sticky" when accumulating enough heat, and thus give much greater adhesion to the road surface, but they also has a much lower treadwear rating (i.e., it wears out much more quickly than the harder rubber tires used for driving on the street).
Drag racing slicks vary in size, from slicks used on motorcycles to super wide ones used on Top Fuel dragsters. For "closed wheel" cars, often the car must be modified merely to account for the size of the slick, raising the body on the rear springs for the height of narrower slicks, and/or replacing the rear wheel housings with very wide "tubs" and narrowing the rear axle to allow room for the wider varieties of tires. Open wheel dragsters are freed from any such constraint, and can go to enormous tire sizes. They use very low pressures to maximize the tread contact area, producing the typical sidewall appearance which leads to their being termed "wrinklewall" slicks. Inner tubes are typically used, to ensure that the air does not suddenly leak catastrophically as the tire deforms under the stress of launching.
"Wrinklewall" slicks are now specifically designed for the special requirements of drag racing, being constructed in such a way as to allow the sidewall to be twisted by the torque applied at launch, softening the initial start and thus reducing the chances of breaking traction. As speed builds, the centrifugal force generated by the tire's rotation "unwraps" the sidewall, returning the energy to the car's acceleration. Additionally, it causes them to expand radially, increasing their diameter and effectively creating a taller gear ratio, allowing a higher top speed with the same transmission gearing.
Since slicks are outlawed on roads due to their inability to handle wet pavements, the bias-ply "cheater slick" became popular in the in the 1960s. It was a typical slick-type tire, but engraved with the absolute minimal amount of tread grooves required to satisfy legal requirements. Since then, however, tire development has progressed greatly, so that today's muscle cars typically use wide, grooved radial tires which perform better than the slicks of the past.
The development in cheater slick technology has affected the development of tires for racing series other than drag racing as well. When other forms of auto racing similarly instituted classes which require DOT-approved street tires, some manufacturers similarly began to market tires which superficially resembled their high performance street tires, but with the least tread pattern permissible and with very soft, sticky rubber, intended specifically for competition because the soft tread would wear too quickly for street use. These became known, loosely, as R compound tires. With additional years of progress, this class of tire has in its turn followed its own line of development, to the point where they have little in common with true street tires of the same brand. This has led to new classes of racing which require not only DOT approval, but also a minimum treadwear rating, in an effort to eliminate the R compound tires from competition and require "true" street tires.
At the track, bias-ply drag tires will produce a lower ET- but only marginally. But the bias-ply tire’s got a problem- it cannot handle things like bumps and corners as well as a drag radial can, which is exactly the sort of stuff you’re probably going to encounter driving to and from the track. In other words, a modern drag radial can give you up to 90% -percent of the traction you need and still get you home safely from the dragstrip without the need for dedicated wheels and tires for the track or a truck and trailer.
There are two kinds of DOT drag tires- radials and bias-ply construction. Drag radials provide a sturdy sidewall for cornering and ride. They also have less rolling resistance than bias-ply tires. The caveat to a drag radial is the compound. They use a special soft compound, which is good for the track, but driving them on the street is going to eat them pretty quick, especially if you enjoy occasional stoplight-to-stoplight runs.
Every manufacturer has their own rubber compounds. The tread compound not only determines the life of the tire, but also the length of the burnout. Regular street tires typically do not like burnouts- the heat makes them greasy and slick, though some high-performance street tires (such as the BFGoodrich Radial TA KDW) like a short little burnout.
Generally, drag radials need less burnout (i.e., should be heated to within 15 degrees of the track temperature), because the special compounds that make them streetable get gummy when they are heated too much. In fact, the ET Street and Street Radial tires only need a short spin to haze the tires as they heat up quickly. This brings the special compounds to the surface, increasing the stickiness of the tire. If you put too much heat in them they start to ball up, kind of like when you rub an adhesive and get little balls of goo. That balling up can actually work against you, slowing down the car in the first 60 feet. In the end, you need to take the manufacturer’s suggestions and experiment with your car.
Another aspect of the rubber compound of a drag radial is its longevity. In order to provide the grip, the compound is considerably softer than a stock or even an ultra-high performance street tire. That grip comes at a cost of lifespan. It all depends on how often you are going to run them. Keeping them properly stored for the majority of the time will add to their life. On average, a set of drag radials, with a mix of track time and highway miles, is between 3,000 and 5,000 miles. Nitto, however, claims that its NT555R tire will last up to 10,000 miles.
There are a number of excellent drag radials available for both track/light street and street/track. Here are the most popular brands:
Street and Track
- Mickey Thompson ET Street (I and II)- The ET Street is designed for limited street use and will last less than 7,000 miles. M/T’s ET Street Radial is world-renowned for its hardcore drag racing capabilities and have clocked 6-second quarter mile times. The ET Street Radial II is made from the same compound as the Street Radial I, though it is designed for better wet weather traction, due to the increased number or rain grooves. The Street Radial II is mainly designed for 17-inch+ wheel combinations.
- Toyo Proxes TQ- Toyo uses a unique compound that is designed for both IRS and solid axle rear ends. Much like the M/T ET Street, it can be driven on the street and strip but its 00 treadwear will put life expectancy at around 7,000 miles or less (depending on how much you go to the track).
- Nitto NT05R- This is Nitto’s newest drag radial that is based on the tread design of their NT05 Ultra High Performance road handling tire. This is a single 0 treadwear tire and will last slightly longer then the other tires in this class. While this is intended to be a track tire, it can also be driven on the street. It is available in sizes ranging from 275/40-17 all the way up to 315/35-20.
- BFGoodrich g-Force T/A- Also sporting a 0 treadwear like the Nitto NT05R, the BFG will last closer to 10,000 miles while doing a decent job during wet weather situations with its integrated rain channels. BFG’s Comp T/A drag radial was the first ever drag radial to meet DOT street tire standards. The main differences between the two tires is that the new g-Force offers a broader range of performance. The g-Force T/A was the spec tire in the NMRA Drag Radial category for many years and is a proven 7-second tire.
- Nitto NT555R- Nitto’s NT555R has been a very successful tire, especially in the t model muscle crowd, for its dual purpose street/strip use. With its 100 treadwear and improved water channels, The NT555R can live for around 10,000 miles and combat wet weather situation; it is the longest lasting drag radial.