Sprint Car Tire Tech and Maintenance
When you are wheeling a 700-950 HP beast around a ¼ - ½ mile racetrack, there is not much that is more important than being able to get all that power from the motor to the ground. That is where the tires come into play. There are many different tips and tricks when it comes to tires that will help you not only get your power down into the racetrack, but some that may also help your tires last as well. Here, I will outline some of the processes that I use when it comes to tires.
First, we will talk about new tires. Many people think that just because you have a new tire, it is simply ready to bolt on and go, but that is not the case in this day and age. With the power that these cars are putting out now, every little advantage you can gain with traction is critical. Once you get the process down, it almost comes second nature, however it is a long and grueling process to get the tires right.
Generally, you buy a tire based off of the chalk mark. The chalk mark is a factory mark that will give you a general ideal of what the tire will measure when it is mounted. Sometimes however, it is not totally comparable to what it actually measures. When you first buy a tire, you will mount and measure it. Sometimes it does not roll out to your liking, say it is small, I typically pump the tire up to 25 pounds and let it sit out in the sun for an hour or two, that will grow the tire, you can typically gain ½ inch or more using this method.
Once the tire has sat for a while, bring the pressure back down to your measuring point and roll the tire out again, if it measures where you want, then you can move on to balancing. I always tried to do this with all tires on the same wheel, that way you will know if you have a tire that is way off balance. We always sent the tire back if I had to add more than 5 sticks of wheel weight. I use the Quick Stick Wheel Weights, part number 910-100361. I had these sticks cut in half so each stick weighed 1.5 oz. If the wheel balances out, you can move on to grooving and siping.
Next step, is to groove and sipe the tire. I use Van Alstine G-1000-M Instant-On Tire Groover, part number 910-82055. I also use Deluxe Grooving Iron and Multi-Blade Siper Kit, part number 910-82076. These are the two tools that I have found work the best for me. Also, our friends at EMI have created some very handy grooving and siping charts for tires, you can see the charts by clicking the link Here.
Of course, many people find their own grooving and siping methods and patterns that work for them, with some trial and error you could find your own as well. Grooving will cut larger slices in the tire, essentially splitting one tread block into two for added traction. Siping is the process of adding a razor blade cut no deeper than half the tread. Sipes will allow the tire to gain heat quicker, thus making the tire come in and start working sooner, but will also allow the tire to dissipate heat sooner preventing the tire from becoming too hot and hopefully preventing blistering.
After grooving and siping, I will typically re-measure the tire to be sure on my size, then mark the tire with the size, dismount, and move on to the next.
With used tires you have no grooving or siping to worry about as this should already be done. There are a couple other steps that need taken with used tires.
First, when it comes to wash day do not forget the tires! It is extremely important that the tires get cleaned as well as, or better than, the race car. The reason for this is because any dirt that is left on the tires from a race night will help that tire harden, or “seal over”. I suggest using a simple green/water solution for soap. Spray the tires down thoroughly and let it sit for 10-15 minutes or so, then go around with a pressure washer and wash the tire. If there is still dirt on the tire, repeat the process. Essentially, this is the only “maintenance” that needs to be done to used tires. Once washed, reset the pressure to your base for that tire and re-measure the tire, marking down the measurement and crossing off the old measurement, then you are good to go.
- Grinding your tires. I suggest grinding your used tires to take the top “seal” off of the tire. After the tire has a heat cycle, there is a chemical reaction in the tire that will cause the rubber to harden, or “seal over”. Grinding will take this top seal off of the tire and open the pores back up at the surface making the tire grip the racetrack better.
- Check tire heat after a run. Tire heat will tell you what you need to do with the race car. If the outside of your LR tire is warmer than the Inside of your LR tire, that means that you have too much stagger. Adversely, if the inside is warmer than the outside, that means you have too little stagger. I like to check the LR for this, as the RR is always very hot after a race because of the bigger circumference and higher pressure. Visually, you can look at the RR to see what the car needs. If the inside is blistering you have too much stagger, if the outside is blistering you have too little stagger. If it is even wear across the rear tires, you are very close on where you needed to be with stagger.