Mickey Thompson Pro Bracket Radials-The Perfect Tire?


Mickey Thompson introduced their new Pro Bracket Radial for the 2015 season.

Drag race rear tires come in two basic flavors, bias ply and radial. Bias ply is by far the most common and is still the only kind of tire found on fuel funny cars, top fuel, pro stock and pro mod race cars. Radials are really gaining ground in stock/super stock, bracket and outlaw heads up racing.

Construction of a radial tire is just what its name implies, the carcass, or "body," of the tire is manufactured with the cord plies running 90 degrees perpendicular to the direction of rotation. In other words, the cord runs straight across the tire from the inner bead to the outer bead. Bias ply tires on the other hand, run diagonally across the tire at about a 45 degree angle to the direction of rotation from bead to bead.

Bias ply drag slicks have very soft sidewalls. Their footprint elongates nicely at launch making the contact patch larger and the soft sidewalls help soften the hit to the tires. But the tire elongation can lead to tire shake if the tire doesn't quickly return to a round shape immediately after launch. To accomplish this, the race car has to be setup to create a bit of "wheel speed" right after launch, which is basically controlled tire spin which allows the centripetal forces to push the tire outward into a round shape again. In other words, a good launch on bias ply tires usually requires a bit of spin.

Drag radials on the other hand need to "dead hook" and not spin. From the moment of launch until the finish line, drag radial tires are happiest if they never spin. One advantage to drag radials is that the tread doesn't change profile when the sidewalls flex, bias ply tires distort the tread when the sidewalls flex. If you get to compare some bias ply tires in the staging lanes to radials, you'll see strange wear patterns on the bias ply tires, it often looks like there are two grooves of rubber either side of the tread center that get less wear than the rest of the tire. Drag radials on the other hand, just wear evenly across the tread.

Another drag radial advantage is lower rolling resistance than bias plies. This means the tire absorbs less horsepower leaving more power to propel the car forward. All else being equal, you'll run faster on radials.

Drag radials need to dead hook at launch and stay hooked because if they spin, they stay spinning. In racing, the ability of a tire to spin and then stop its spin is referred to as recovery. Bias ply tires have good recovery characteristics, after all they need to spin a bit to perform their best. Drag radials on the other hand, once they start spinning they don't recover well. This is why a lot of drag racers use their bias ply tires for consistency, they know that if they slip a little, the tire will recover and they won't be far off their mark. But if the racer needs to be quick, for example Stock Eliminator class competition, then they'll put on their drag radials and risk the spin in exchange for maximum quickness.

 

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