While the wheel is dated at 3,500 BCE, the tire is a much newer invention. Many of the names involved with the development of tires are still around today.
In 1844 Charles Goodyear patented (U.S. #3,633) the process to create vulcanized rubber. He discovered that if the rubber was combined with a curing agent, in this case sulfur, under high heat and pressure, the rubber could be shaped and formed. Without delving back into high school chemistry, the sulfur atoms form links between the chains of rubber molecules increasing strength, durability, heat resistance, and reducing stickiness.
Just three years later a 23-year-old Scotsman named Robert Thomson patented (U.S. #5,104) the pneumatic tire in the U.S. Thomson inflated an elastic belt of “sulphurized India-rubber” to “present a cushion of air to the ground or rail or track on which they run.”
The biggest step for tires came in 1895 when Michelin, after pioneering detachable bicycle tires earlier in the decade, fitted a set of pneumatic tires to the car l’Éclair for the Paris-Bordeaux-Paris race. Michelin would later pioneer the radial tire in 1946, making its marketing debut in 1949.
Prior to 1946 the typical tire construction was a bias ply. These rubber-coated fabric plies ran diagonally down one sidewall, across the tread and up the other sidewall. The plies alternated in opposite directions. The fabric improved from cotton to rayon to nylon to polyester over the years, but the basic construction hasn’t changed. Radials also use fabric plies, but just one or two plies and they run straight across the tire from bead to bead. Belts — plies with diagonal cords of fabric or steel — run the circumference of the tire. Radials run cooler, have a wider footprint, and a longer tread life, while bias ply construction results in a stronger sidewall (think drag racing benefits) and are generally cheaper.
Tire tech has progressed steadily. Radials became standard on all new American cars in 1983, pushed by consumers wanting better fuel economy (due to less rolling resistance). Now bias-ply tires occupy a niche market for period-correct users and a large segment of the drag-racing market. Radials represent over 98% of all tires sold today.
So all of that history is distilled into what you ride around on every day. That’s all well and good while the tires are in good condition, but what do you do when it comes time to replace them? eBay Motors Tire Center (http://parts.motors.ebay.com/tires) is the place to shop for direct replacement or upgraded tires.
Before buying, you’ll need to know some important information. Along the sidewall there is a series of letters and numbers, something like P215/60 R 16 95V. The P stands for p-metric, which is used for passenger vehicles such as cars, light trucks, minivans, etc. T stands for temporary spare and LT for light truck-metric — oddly enough for medium-to-heavy-duty trucks. The 215 identifies the section width in millimeters. The section width measures from the widest point of the outer sidewall to the widest point of the inner sidewall when mounted and measured on a specified width wheel. The 60 is the sidewall aspect ratio. This is the sidewall height (from rim to tread) expressed as a percentage of the section width. R is for radial construction, B would be for belted (send a picture if you find one of these, I’ve never seen one), and D is for diagonal bias ply construction. The 16 is for the tire and wheel diameter to be matched together. The final digits are the service description. The number represents the load index of the tire (the higher the number the higher weight the tire can support safely) and the letter is the speed rating (the maximum speed capability of the tire).
The latest breakthrough in tire technology is the airless tire. Michelin’s Tweel and Bridgestone’s Air-Free Concept Tire are some of the bigger names in the developing market. The Tweel is a combination tire and wheel using polyurethane spokes inside of a band of molded tread. The hub consists of deformable plastic matrix that can flex under load and return to their original shape. Bridgestone’s design debuted at the end of 2011. The internal spokes are a recyclable thermoplastic resin that gives the tire/wheel its shape, flexibility and strength. A rubber tread is on the outside to provide a traditional contact surface.
There are exciting advances to come in tire and wheel technology, but for the time being, just be glad you don’t need to shod a Bugatti Veyron. A set of the Super Sport’s Michelin tires costs $42k and they’ll last 10k miles — if you don’t treat it like a Veyron. The real kicker is on the third tire change, you’ll need to swap out the wheels — to the tune of $69k — to ensure a proper bead seal.
Visit eBay Motors Tire Center for the proper fitment of your vehicle
Read part 1 of Wheels and Tires 101, Part 1