Pete McDonald feels about tires the way Walt Disney probably felt about mice—not passionately but with a consuming professional fondness. As chief of design for the Firestone Tire and Rubber Co., McDonald, 52, estimates that 100 million tires bear his imprint. Because man does not live by tread alone, McDonald also produces tire art. He has created bookends out of tire models, oil paintings from photos of tire particles enlarged 50,000 times, and even a five-foot-high stained-glass window in a pattern based on a tire print. A show of his artwork is touring Ohio, and the very thought of it makes McDonald rhapsodic. "We've got beauty all around us," he says dreamily, "even in the depths of our tire plants."

Apart from beauty, tires provide information that only an expert like McDonald can translate. Since 1976 his knowledge of the distinctive "fingerprints" created by tread wear and design has helped police solve five homicides. His method: matching tracks at the scenes of crimes with tires on the cars of suspects. "Working in criminal investigations has been fun for me because I'm still batting a thousand," says McDonald. "I've correctly identified the tire in every case." Last year, working from a Polaroid snapshot of a tire print left during the kidnap-murder of a 19-year-old Akron girl, McDonald told police to look for a car equipped with a special model of Duralon tires. When a suspect was arrested, McDonald smeared ink on the man's tires—which were Duralons—drove them over white cardboard and made a positive ID. The suspect was convicted and sentenced to life in prison.

The case that got McDonald started in sleuthing was the 1976 murder of two prostitutes in Monterey, Calif. Police there sent a tire print photo to Firestone, and a co-worker left it on McDonald's desk with the note, "You won't be able to recognize this, will you?" "I never would have gotten into this if it hadn't been for that note," says McDonald. "I liked the challenge. First I decided it was a nine-rib tire—ribs are the traction elements of the tread—even though the whole width wasn't shown. Then I deduced there was a good chance it was a Parnelli Jones Firestone. I asked one of our draftsmen to transpose, from our drawings of that tire, a single groove on transparent paper to use as an overlay. It fit the photo like a glove." All tire sales are recorded by the company that makes them, so Firestone paid for a registration check to find out who in the Monterey area had bought the high-performance Parnelli Jones model. Eventually one of the purchasers confessed to the killings.

Tires of the same design are virtually identical when new, says McDonald, but every worn tire is unique. "Previously police thought that only the brand name of a tire could be identified, but I can do that in less than a day. The laborsome bit is studying characteristics, so I can make an absolute identification." For that he needs a good photo of a tire print that has been lighted from both sides. Even better is a plaster cast of the tire impression. "Ideally, I'd like to have two feet of cast, if possible from dental plaster, that includes two wear bars [strips of rubber that emerge on a tire's surface with wear] and a significant section of the noise treatment [grooves of varying lengths that reduce hum]. Of course, I also look for the obvious things," he says, "an embedded stone, a tear or a repair of a nail puncture."

McDonald grew up in suburban Shaker Heights, Ohio, graduated with a degree in architecture from Miami University of Ohio, and joined Firestone after two years in the Army Corps of Engineers. Once widowed and once divorced, he has a grown son and daughter from his first marriage and plans to marry for the third time this spring. He and his fiancée, Linda Sanders, will live in his spacious lakefront home in Hudson, Ohio. Meanwhile he has begun lecturing police on the importance of preserving tire track evidence, and currently has five cases pending. Someday, perhaps, he may duplicate his triumph of three years ago, when his examination of a single tread mark near the scene of a murder in Nottingham, Pa. cleared a prime suspect and helped lead police to the true killer. "I got great satisfaction helping that guy out," he says. "Maybe that's even more important than catching murderers."