In several posts on this site, I’ve mentioned that tires are among the most significant factors in racing performance.
Think about it! In all racing you’re driving your car as fast as you can maintain control of it. Or maybe, as fast as it will go!. When you lose control, the cause is usually the tires losing their grip on the pavement. That’s when you slide through a turn, spin, or otherwise go in a direction you didn’t intend.
So if your tires lose their grip more easily you can’t drive as fast. In the case of drag racing, the whole issue is acceleration. Drag racing tires must maintain their grip as torque is applied to them. Loss of adhesion may not cause a directional excursion. However it limits the amount of torque the tire can use for forward acceleration.
Tire Ratings
A complex system rates street-legal tires for factors such as load carrying capacity, maximum speed, tread wear, etc. If you want to see what all the markings on a tire sidewall mean, here is a good summary.
The tread wear rating is an excellent indicator of a tire’s “stickiness”. Stickiness refers to it’s ability to maintain its grip with high force applied to make it slide. The tread wear rating number is a percentage of a “standard”, defined as 100. A higher rating means the tread lasts longer before wearing down to the bottom of the grooves.
High mileage street tires can have ratings as high as 400 or more. The stickiest race tires have ratings as low as 40 or less. Obviously the compound in the racing tires is very soft so it grips the pavement very strongly. It’s truly amazing how a new race tire grips. On the other hand, these tires don’t last long. In active weekend racing, you might wear out two or more sets during a season. In autocrossing this is the most expensive aspect of the sport for most racers.
The sticky low-tread-wear-rating tires are technically street legal. I would definitely not recommend them for anything but extremely short (less than 10 miles) stretches on the street. Their soft compounds make them extremely vulnerable to damage. Also they just wear out too fast to be practical for street use.
What about “cheater” tires?
In recent years options have included street tires with tread wear ratings in the range of 100-150. These grip very well and are suitable for street use. However they won’t run 40,000 or 50.000 miles like a “turnpike” tire. They can work as dual purpose tires, for driving to events and racing.
Keep in mind that my experience is now a few years stale I found that a new set of race tires will far outperform these “cheaters”, initially. By “race tires” I mean the ones with tread wear ratings of 40. However, the race tires lose much of their superior grip after just a few events (heat cycles) even though they’re not physically worn out. At that point the cheater tires I started using performed nearly as well as the not-so-new race tires. They’re also cheaper and more practical for multi-purpose use.
Are you a serious competitor and willing to spare no expense to win? By all means go for the race tires.
With that said, new options appear at least every season, and sometimes during the season. What I experienced may not be what you do. As I pointed out in another post,Tire Rack is a great place to get current information and advice.
Keep watching this space – there will be additional material periodically.