R-Compound Tire Tech

If your going to use a R-compound tire this is what you need to know about them.

R-compound tires including DOT spec are much softer compound than summer performance tires with much higher levels of grip. The rubber compound when heated through friction gets sticky and soft and grips the track surface. Even though there is no standard between manufacturers the tires UTQG treadware rating is an indicator as to how sticky the tire will be. A 100 UTQG tire from Hoosier may be a softer or harder compound than a tire of the same treadware rating from Yokohama. It is also known that sometimes a manufacturer may make a 100 UTQG tire that is in fact softer than it's treadware rating indicates. So treadware rating means next to nothing. Yep!

The tire compound will become harder every time you heat the tire up and cool it down. This is called vulcanization or more commonly refered to as heat cycling. Heating the tire causes the molecules in the rubber to cross link and form a strong matrix. This can be good or bad. If your just using the tire for lapping the harder cross-linked rubber will last longer which is a good thing. But for race day the overall grip will decrease. The fastest tire is the one that sees the least amount of heat cycling. You can also order tires from retailers that have already been heat cycled if it's going to be used for lapping for a small extra charge.

DOT R-compound tires have minimal siping to allow water to evacuate from the tire surface in wet conditions. The TOYO Proxes R888 I run is pretty good in everything but standing water. I have driven it in moderate and heavy rain and on well drained roads it was stuck to the road surface pretty well. If you don't plan on using these in the rain you can usually have the tread shaved off from the vendor which removes much of the siping resulting in less squirm due to the thinner layer of rubber, but your performance in the rain will be gone.

Nitrogen... Why not air? Yes air is 78% nitrogen. So how much better can pure nitrogen be. The advantage nitrogen has it that it expands and contracts less than air. You will see more stable tire pressure. For someone driving on the street this is a waste, but if your serious about your tracking nitrogen is what you want. When the tire is mounted either a vacuum source needs to be put on the tire to remove the air or several fill and deflate cycles need to be done to get all the air out. Another thing to consider before using nitrogen is do you have a nitrogen source available at the track in case you have to increase your tire pressure? Adding a small amount of air at the track likely won't affect anything.

Before getting out on the track inspect the tires well. Look for foreign objects stuck in the tire. If the foreign object penetrates through the inner wall of the tire get rid of the tire. Don't patch it. Replace both tires on that axle so that handling is symetric. Tires are expensive, but a blowout at high speed is more expensive. Look for rub marks on the tire where it may be touching the body or suspension components. Check the tread depth and make sure it's adequate for the track time your going to put on it.

Get a good road force balance and make sure you use aluminum tape to keep the weights on and you should be good for your next track event.