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

18 - Will Shaving Your Road Course Tires Actually Make Them Last Longer?
Yes, this is true and something I addressed in a recent "Contact Patch" column. To recap: One of the reasons radial racing slicks are so effective is because they feature shallow tread depths and their contact patch acts as a single unit-they don't have normal tread blocks. Basically, any tread design breaks the contact patch down into smaller elements, and additional deep tread depth (required to enhance wet traction) allows tread-block squirm, which will reduce dry performance.

Again, the folks at Tire Rack explain that shaving a tire is an effective means of permitting more of a tire's performance capability to be realized earlier in its life. A shaved tire's tread profile will usually result in a slight increase in the width of the tire's contact patch, putting a little more rubber on the road. The resulting shallower tread depths reduce the tire's slip angle, increases its responsiveness, and helps stabilize its cornering power by minimizing tread-block squirm. Minimizing tread-block squirm also reduces heat buildup and the risk of overheating its tread compound. In many cases, shaved tires used in competition or at driving schools may actually have a longer useful life than tires that begin being run at full-tread depth.

19 - What Are Tire Speed Ratings And Where Can I Find Them?
A tire's speed rating is expressed as an alpha-numeric symbol you'll find on your tire's sidewall that tells you the maximum sustained speed the tire is capable of safely handling. An H-rated tire, for example, is built to be safe for continuous operation at speeds up to 130 mph. Most current model year family-type cars have S (112 mph) or T (118 mph) speed ratings. High performance cars often have tires with a V (149 mph) or ZR (in excess of 149 mph) speed rating. A few ultra-performance cars have W (168 mph) and even Y (186 mph) speed-rated tires.

You will find this speed rating expressed one of two ways. One, as part of the tire sizing information, such as 275/40-ZR17, a ZR rated tire. Or, you may also find it expressed as a numeric-alpha "Service Description" such as 92 V, typically printed on the tire's sidewall behind the size info. This is a combination of load rating (92) and speed rating (V).