DRIVE TIME
Few notice where rubber meets road
By Mike Leidemann
Advertiser Transportation Writer
The only time most of us think about tires is when they go flat.
Still, tires probably are the single most important part of our commuting experience, where the rubber meets the road. They play a key role in the safety and efficiency of daily driving. A properly cared-for tire can save you hundreds of dollars each year and spare you the frustration of a highway breakdown.
There's a ton of useful information molded onto the sidewall of a tire, but most of us don't know how to read it. Printed there is the name of the tire, its size, whether it is tubeless, the government grade, maximum load, and more. Here are a few hints on how to decode the information on the sidewall. Example: P215/65R15 89Q P: The tire is meant for use on a passenger car. 215: Width of the tire in millimeters from sidewall to sidewall. 65: The ratio of height to width; this tire's height is 65 percent of its width. R: Radial construction; B means bias-belted construction; D means diagonal bias construction. 15: Diameter of the wheel (rim) in inches. 89: Load index, the maximum the tire can carry according to an industry standard. With an 89 rating, this tire can carry a maximum load of 1,279 pounds. Q: Speed rating. The usual American system goes from Q (maximum speed of 99 mph) to Z (more than 149 mph).
OK, most of us know that intuitively, even if we don't think about it all the time. But I'll bet there are lots of things you didn't know about your car's tires, unless you've seen the new reference guide being passed around by Goodyear.
How to read a tire
Did you know:
- The parts of a tire include tread, which provides traction; belts, which strengthen the tread; the sidewall, which protects the side of the tire from road and curb damage; the body plies, which assure an airtight fit with the wheel; and the inner liner, which keeps the air inside the tire?
- An average 21-pound passenger tire is made up of 4 pounds of natural rubber, 5 pounds of carbon black, 1 pound of steel cord, 1 pound of polyester and nylon, 1 pound of steel bead wire, 3 pounds of 40 different kinds of chemicals, and 6 pounds of five different kinds of synthetic rubber?
Probably more important is that most people don't know how to care for their tires properly. Recent studies by the National Highway Traffic Safety Administration show that 25 percent to 28 percent of all cars in America have at least one tire seriously underinflated. Another study showed that 67 percent of drivers had failed to rotate their tires in the last year, as recommended by most manufacturers.
Underinflated and unevenly worn tires contribute to many accidents. Moreover, running a tire 20 percent underinflated — only 4 to 5 pounds per square inch — increases fuel consumption by 10 percent. It also reduces the tread life by about 15 percent. That can add up to a lot of extra expenses over the course of a few years.
The Rubber Manufacturers Association recommends that motorists take five minutes every month to check their tires, using a four-part procedure:
- Pressure: Make sure your tires are inflated to the manufacturer's recommended specifications, which are usually found in a car owner's manual or on the inside of a car door.
- Alignment: A bad jolt from hitting a curb or pothole can throw your front end out of alignment, causing tire damage. A shuddering or vibration coming from the tires usually indicates a problem with alignment or uneven tire wear.
- Rotation: The general guideline for tire rotation is approximately every 6,000 miles. This will minimize problems on the road and increase the life of your tires.
- Tread: Advanced and unusual wear can reduce the ability of tread to grip the road. If the tread is worn down to 1/16 of an inch, tires should be replaced.
With regular checks like these, good tires should last anywhere from 40,000 to 80,000 miles, the Goodyear guide says.
Now all you have to worry about is getting a flat.
Mike Leidemann's Drive Time column appears every Tuesday. Reach him at 525-5460 or mleidemann@honoluluadvertiser.com.
Correction: The manufacturer's recommended pressure for automobile tires usually is found in a car owner's manual or on the inside of a car door. Other information was contained in a previous version of this column.
