Talking Tire Basics

The right tires can bring an older car back to life, tighten up a sloppy handling, quell apprehension on wet, curvy roads, and silently perform years of faithful service.  The wrong tires, on the other hand, can make you think the shocks and bushings have failed, the alignment is out of spec, the steering is demon-possessed, and the water on the road is a foot deep.

Tires are the single most important component on a vehicle. And yet, despite advanced computer simulations, designing and developing a tire remains as much art as science. With a tire, improvement in one performance characteristic almost always comes at the expense of another. Sometimes, the interactions don’t work the way tire designers’ computers predict.  This is due partially to the tire literally being cooked (or “cured”) in the manufacturing process: Polymers, sulphur, carbon black, oils, waxes, resin, and structural components evolve and develop new properties. Some of this evolution continues over the tire’s life, especially if the tire is overheated. With the latest tire production methods, which lay individual cables of material rather than sheets of fabric or steel. 

Auto manufacturers spend millions of dollars on their vehicles’ suspension engineering and chassis tuning, including factory tire fitment. Any change you make after you buy a vehicle means a trade-off must be made. The more dramatic the change, the more severe the compromise. The best general guidance regarding plus-sizing is to look to the automaker’s own offerings. If a car is available with 18s, then rest assured, the suspension and braking is engineered to work effectively with this heavier setup.

Among the factors that influence tire performance is how recently the tire was crafted. Tires bear a “born on” date. Imprinted on one or both sidewalls is an alphanumeric code of a dozen or so letters and numbers that begins with “DOT.” Tires produced starting in 2000 have a four-digit birthdate code at the end of the DOT number. The first two numbers indicate the week, and the last two the year. This date is important because rubber deteriorates with age. A tire that’s been in service for five or six years should be replaced regardless of tread depth. Cut a year or two off that for vehicles that are not garaged during the day or are run in areas of high ground-level ozone.

The greatest factor in tire longevity is the roads on which you drive. Tire companies have mapped out average tread life by county and discovered that tread life is inversely proportional to local elevation. Maintenance is the key to getting the most mileage and performance from your tires. Each month make sure pressures are at least what the vehicle manufacturer recommends, rotate positions every 3,000 miles, diligently check for signs of uneven wear, and correct any vehicle problems that can cause poor wear. Whether you’re buying a new vehicle or replacing old tires, it pays to have a solid understanding of this essential automotive component.

You can basically group tires into the following…

  • Economy Tire – Round and black. They hold air, last a long time, provide a comfortable ride, and don’t cost a lot.
  • Touring – While comfort and long-life are top priorities in this category, precise steering feel and a more controlled ride are important as well.
  • Grand Touring – These tires offer sportier steering feel, tauter ride, and enhanced grip.
  • High-Performance – Grip, both wet and dry, and crisp steering feel are at least as important as tread life and comfort.
  • Ultra Hi-Performance – Grip is king, and precise steering is queen. Tread life and ride comfort take a back seat.  Street slicks would fall in this group.