measurement of a tires performance
The Usual method is mount to a rim and take the car to a race track and push it to find the slipping point. This measures the dry traction. Better the tire, more grip you would have and faster you should be able to take turns. There are different rating for tires. Standard H rated tire is difficult to measure because it is ALL season tires that must perform under all different weather conditions. Q rated tires are snow tires. and Z, Y, W, V ratings are currently used for street summer only tires. R rated tires are street illegal, and should only be used in a race track. The manufacturer of the tire sets these ratings based on the tire compound used, and tread pattern. Each of these ratings have associated safe speed range. Racing tires usually have side wall reinforcement so that you safely push 150+ MPH without worrying about tire blow out problem.
There are many objective ways to measure a tire's performance. Lateral, steady-state cornering grip (usually measured on a skidpad), braking distances, transitional response (such as an emergency lane-change test), road noise, ride quality, and treadwear can all be measured, but these tests usually require specialized instrumentation under controlled conditions to do so. In addition, a tire's performance can be measured subjectively, by way of the driver's impressions. Such characteristics include steering feel, compliance, how progressively the tires give up grip, etc. Obviously, these types of ratings are heavily influenced by whomever happens to be behind the wheel at the time. Bear in mind that ride-and-handling engineers often work with tire manufacturers to set up the car to perform optimally with one particular type of tire (Patrick Bedard, or possibly Csaba Csere, of Car and Driver magazine wrote an excellent column some months ago about this, citing the current Ford Mustang's development as an example). Thus, changing tires on a vehicle can adversely affect the car's performance, even the tire in question may not be a 'bad' tire.
