How the heck do I measure tire life?

[Tsurara]

So in SCCA Touring groups, we are allowed a maximum of -2 degrees of camber, which, as you can imagine is magical for tire wear.

I managed to score some used tires off of a race team which I have been using for the season thusfar. I figured one of the sets would be corded by the end of a race at NHIS, but they still appear to have a good amount of life left, but I can't be sure as I mostly wear the outer edge.

Is there any way at all to measure how much life I have left on a specific set of tires or will I have to guess? I mean, normally I'd do tread, but these Hoosiers don't have any. Any feedback would be appreciated. Thanks!

[SSNH]

6. How do I know when it is time to replace my R6/A6 competition radials?

Located on the tread surface of the tires are small divots or holes. These divots are called tread depth holes and are used to measure the wear of tread. Tread depth is usually referred to in 32nds of an inch. A brand new tire should measure 4/32 of depth in each of the holes. By keeping track of the number of laps on each set of tires and measuring the depth of tread, you can calculate how much wear is left in the tires. When the holes are completely flush with the tread, it is definitely time to change to a new set of tires. There is tread rubber under the depth hole and the tire can continue to be run, but the driver must be aware the performance level will be at its lowest. When this rubber below the depth hole is gone, you will then see the first layer of cords. At this point, the safety of the tire is now compromised and the worn tires should be replaced.

The driver must be the ultimate measure of when to replace the tires. There might be measurable tread depth on the tire, but the performance (grip or handling) of the tire might be low. To get the most wear out of your R6/A6 competition tires, be sure to rotate front to rear or side to side after an event.

When to Buy New Tires

Ever wonder when to buy that new set of tires? Can you get another week out of the old set and still be competitive. If you keep good notes then you can get an idea of when to step up for some new boots.

You can use a durometer and track the hardness of the tires from when they are new and log your tests results as they age. The tires will harden with age, which can be tracked with a durometer. When using a durometer make sure that the durometer is used on tires of the same temperature to insure relative measurements. Hot tires are going to be softer than cooler tires. You will notice that tires sitting in the hot sun are softer than those that are shaded. You can use a pyrometer to improve the consistency from durometer readings.

You can also track the tire temps after a run. New tires make more heat than used tires. Worn out tires will not produce as much friction to produce tire heat. By tracking the temperature of the tires after a run, you will learn to anticipate when the temps are falling off too much. If you are diligent in your monitoring you will know when to hit the tire truck for that new set.

You can also use a tread depth gauge to check the amount of tire wear. On many tires, the grip falls off dramatically at a given wear depth. When you feel like your tires have quit, then check the depth with a tread depth gauge and write the numbers in your notebook. You will learn to anticipate when you are approaching the wear depth that makes you want a new set. Over time you can learn to predict when you have gotten the most out of your set of tires. You may find that the fall of in each corner is a bit different. The LF may work to a deeper depth than the left rear because it does not go through the spinning created by your awesome horsepower.

Another good idea is to track is the number heat cycles your tires experience. Each time your tires get hot they release chemicals from deep within the rubber. As the chemicals are released the tires lose some of their grip. You can see tires that are hardly worn lose their grip due to heat cycles. Count the number of heat cycles that your tires go through and you may find a repeatable pattern that lets you know when to get that new set.

Tread Depth Gauge:
http://www.longacreracing.com/catalog/i ... 37&catid=9[/quote]