It's a Drag - How Drag Slicks Work

Slick distorts during launch to maintain traction

You see them on only the most powerful of cars, and only on the strip. These massive meaty mound of round rubber are what powers NHRA cars to 330 MPH, without flying apart all the while looking cool.

The first drag racing slick was developed by a company called M&H Tires (Marvin & Harry Tires) in the early 1950s. It was the only company in the world that produced and sold original drag racing tires. Later, competitors stole or reverse-engineered molds, and began making their own tires.

Drag racing slicks vary in size, from slicks used on motorcycles to very 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 axles 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. Some use very low pressures to maximize the tread contact area, producing the typical sidewall appearance which leads to their being termed "wrinklewall" slicks. A Goodyear tech checks the pressure of each tire of a top fueler on the line to ensure no disasters. Inner tubes are typically used, to ensure that the air does not suddenly leak catastrophically as the tyre deforms under the stress of launching. While Goodyear has the majority of the pro market locked up, other manufacturers such as Hoosier and Mickey Thompson (M/T) are seen regularly.

"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", or "smoking" the tires. As speed builds, the centrifugal force 

Slicks get "taller" as they rotate faster, making the car  faster

generated by the tyre's rotation "unwraps" the sidewall, returning the energy to the car's acceleration. Additionally, it causes the tyres to expand radially, increasing their diameter (i.e. - the tire gets "taller) and effectively creating a higher gear ratio, allowing a higher top speed with the same transmission and/or rear end gearing.

There are some really neat high speed pictures out there capturing the tires as they "distort" during a run - at some points they form a semi-circle, and at other points almost a 3 leaf clover effect is seen.

Slicks get roasted during the burnout. A good thing.

Typically the track is sprayed during preparation with SVT (a glue used to promote adhesion) and during the "burnout" the racer lays down a track of fresh, hot, sticky rubber for which to launch from. There is no problem creating the power to run down the track - the real skill is in managing the tires and clutch packages to deliver the power to the wheels in a manner that won't cause the slicks to break loose and "smoke".

Pretty basic piece of gear, but without slicks, there would be no real drag racing.

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