Jeff Lacina
December 1, 2008
Photos By: Ron Blevins, V6john

11 - Compressed Air Or Nitrogen?
Most race teams inflate tires with nitrogen. Here's why: Nitrogen gas used to fill tires has had most of the water vapor removed. With the water vapor removed, the nitrogen gas will reduce the expansion and contraction of the gas inside the tires as they heat and cool. Bottom line is nitrogen-filled tires will maintain more even pressures during a use cycle, and this can be beneficial whether corner carving or launching down the dragstrip.

This is important in an all-out race car, where small changes in tire pressures will alter the handling of a high-performance car racing at tremendous speeds around a track. However, more consistent and even tire pressures are essentially insignificant to a consumer out on the road. Pure nitrogen in passenger car tires seems like a waste of money, as it costs more than $10 a tire when purchased to have them filled with nitrogen. If you want to keep them filled with nitrogen, you will need to find a tire shop that has the equipment to refill or adjust their pressures, or you can purchase small aerosol refill cans, adding even more expense to something that can be done with simple compressed air.

12 - What Are Tread Wear Indicators?
These are narrow bands built into the tread during manufacturing that begin to show when only 1/16 of the tread remains. Also called wear bars, treadwear indicators are there to provide an obvious visual warning that it's time to shop for new tires. That is, if you ever get to see them before the cords start showing on your old tires.

13 - Do You Know The Three T's Of Tires?
Each and every DOT-approved tire, even full-on competition tires, is required to have three separate ratings: Treadwear, Traction, and Temperature.

• Treadwear ratings differ from Traction and Temperature ratings in that they aren't a measure of a tire's built-in safety margin. Instead, these ratings, represented by a three-digit number, give you an idea of the expected useful life of the tire according to government testing.

• Keep in mind these ratings are relative to each other. For example, a tire with a treadwear rating of 150 can be expected to last about 1.5 times as long as a tire with a treadwear rating of 100. These are just guides, however. Your tires may last longer (or not) depending on such factors as how you drive, whether you maintain proper inflation pressure and rotate the tires per recommendations, and of course how many burn-outs or hot laps you put them through.

• Traction ratings run AA, A, B, and C, with C being the lowest on the scale. These ratings represent the tire's ability to stop on wet pavement under controlled testing conducted by the government. C-rated tires are marginal and should be avoided. Never buy a tire with a Traction rating that isn't at least equal to the minimum rating specified by the manufacturer of your vehicle.

• Temperature ratings are A, B, and C, with C being the minimum allowable for any passenger car tire. The ratings correspond to a given tire's ability to dissipate heat under load. Tires with lower ratings are more prone to heat-induced failure, especially if driven at high speeds (or when overloaded). As with Traction ratings, never buy a tire with a Temperature rating that's less than specified for your vehicle.