Mickey Thompson D-O-T Drag Radials M&H Racemaster certainly isn’t alone in the D-O-T drag radial business. Another big player is Mickey Thompson Performance. According to M/T, their D-O-T drag radials are constructed with the latest in high tech radial manufacturing techniques coupled with their years of drag racing experience and compound development. Typically, M/T incorporates their relatively soft “R2” compound in the tire, which provides for superior traction on the strip. What about sizing? M/T offers a considerable cross section, with common fifteen inch wheel sizes in the following dimensions: P235/60R15, P275/50R15, P255/60R15, P275/60R15, P325/50R15, P295/65R15 and P315/60R15. These aren’t diminutive tires either – the smallest of the bunch (the P235) has a sidewall width 9.5 inches, a tread width of 8.4 inches and a diameter of 26.1 inches. Meanwhile, the big P315 has a sidewall width of 12.9 inches, a tread width of just under 12 inches and a diameter of 30 inches. That’s a serious tire. In addition, Mickey Thompson manufactures a large number of D-O-T drag radial tires in fourteen-inch, sixteen-inch, seventeen-inch and eighteen-inch sizes more suited for sports cars and sport compacts. When using their drag radials, Mickey Thompson advises the tread compound used in the ET Street Radials is designed to heat quickly and does not require a heavy burnout. A dry hop after the burnout is not recommended. As far as drag race operating pressures are concerned, no tire in this series (D-O-T drag radial) should be operated below 11 PSI. For tire sizes of P275 and smaller, they suggest you set pressures between 12 and 16 PSI at the strip. Larger tires (P295 and bigger) should have pressures set between 11 and 14 PSI. For the street, pressures of approximately 75% of the maximum on the sidewall are recommended as starting points. Of course, every car is different, but the above should provide a good baseline. For more information, contact: MICKEY THOMPSON PERFORMANCE |
Meanwhile, the radial construction provides for excellent ride control on the street. In order to make the tires “work”, they use a special proprietary sidewall construction. M/T uses a combination polyester and steel belt construction which they claim adds to the tire life. Tread patterns are directional with low voids. That provides the maximum amount of rubber on the road, but at the same time, still meets D-O-T requirements. 
 When you dig into the specs for street car race tires, you'll often find that some of the tires are heavier than an identically sized slick. Why? There are two reasons: DOT tire requirements and the weight of the car. In order to meet the goals established by those requirements, street car race tires most often require more belt material. This tends to stiffen the side wall and it also tends to add weight to the tire. |
Of course, it's no secret that drag slicks for unlimited applications are often constructed as light as possible. That just isn't the case with a tire that is forced to pass a DOT requirement. A DOT tire must have a load range (and it must have that load range cast into the side of the tire). Using the M&H Racemaster P325-50R15 shown in the accompanying photos as an example, the overall tire weight is 25 pounds + or - (at least on our bathroom scale). FYI, one of M&H’s competitor’s has a similarly sized drag radial that tips the scales at 29 pounds, while another weighs a whopping 37 pounds (that’s definitely portly). In comparison, a similarly sized conventional drag slick tips the scales at approximately 23 pounds. Where does the weight come from? M&H was careful in the design of their tire. That’s why the weight of their drag radial isn’t over the top, but they do point out that a bit more belt material is required in the drag radial tire. This makes for a more rigid side wall and of course, a heavier tire. In simple terms, the manufacturer is forced to build a more robust tire if it has to conform to heavier cars and DOT requirements.
Compounding is another issue that has to be addressed by the manufacturer. There are a couple of different avenues taken by companies who have entered the street car drag racing arena. For example, M&H Racemaster has developed an entire new line of compounds just for their newest "HB" series of street car drag race tires. Here’s how M&H’s compound ratings work:
Compound: Characteristic: As you can see, the HB compound used in the drag radials is on the soft end of the scale. |
Burnouts & Compounding…
The type of burnout you perform is related to the tire compound. Typically for a car equipped with HB11 compound tires, M&H offers this advice: "A hard burnout is not necessary.
For the first pass of the day, make a light to moderate burnout. After that, a light burnout should suffice. Continue the burnout until the engine starts to pull down. A dry hop after the burnout isn’t recommended. For a stick shift car, perform a light burnout, haze the tires and stage immediately. Generally speaking, drag radials work better with a light burnout rather than a hard burnout. Drag radials tires may require a fairly hard burnout on the first and second pass to break them in."
In terms of life, these new generation quickest street car tires are much the same as slicks, and slick life can vary from car to car. According to the experts, inconsistent 60-foot and 330-foot times are caused by tread wear or carcass breakdown. These should be signals that it's time to change tires. While slicks have wear holes on the tread face, street car tires don't. Typically when the grooves in a street car drag race tire are gone, then it's time to buy new rubber (the various sanctioning body rules might also stipulate that some tread must remain). Remember, cars that launch hard can cause the tire carcass material to break down. A good rule of thumb is to inspect your tires carefully after 30 passes. And if the car is very quick, the tires should be inspected more frequently.