”New-tires-on-rear” is a universal axiom propagated by tire manufacturers that doesn't hold up under scrutiny, according to John M. Baldwin, principal scientist at Exponent Inc. and Ford Motor Co.'s polymer technical expert for more than six years.
Extensive testing, plus a thorough review of accident and fatality statistics, doesn't necessarily demonstrate that placing new tires on the front of a vehicle is always dangerous, Mr. Baldwin claimed in a speech at the 28th annual Clemson University Tire Industry Conference in Hilton Head April 18-20.
Mr. Baldwin, who at the time of the speech was transitioning to a new position at Discount Tire Co. Inc., also called out the Rubber Manufacturers Association (RMA) for what he said was a mischaracterization of the tire aging research he performed while working as a tire research specialist at Ford.
In his speech, Mr. Baldwin evaluated common tire industry policies from the perspective of tire retailers.
“In the tire industry, a lot of decisions are based on tread depth,” he said. “But what is the significance of tread depth? There is uneven wear on damn near every tire.”
The general rule of thumb, he said, is to replace a tire when it reaches 2/32 inch of tread depth. “But you don't know what part of the tire you're at. It could be the best or the worst part of the tire.”
Tire age also can't be left out of the equation, according to Mr. Baldwin. Based largely on the results of his testing, Ford recommends that vehicle owners replace their tires after six years regardless of the tires' remaining treadwear.
“The average full-sized spare tire is nine years old,” he said. “You can tell your tire store to take that perfectly good spare tire and put it on your car.
“But if you're in Yuma or Miami, do you really want that nine-year-old spare going on?
“Meanwhile, the average mini-spare is 12 years old,” he said. “That means you're screwed.”
As for new tires, the RMA position is that they go on the rear of a vehicle unless the tires have a low speed rating, Mr. Baldwin said. This common wisdom is backed in videos by Tire Rack Inc., Michelin North America Inc., Continental Tire the Americas L.L.C., and others depicting the dangers of fitting two new tires on the front of a vehicle.
Ironically, Mr. Baldwin's new employer, Discount Tire, also supports this position and publicizes it on its website.
“The industry's position is that if you put two new tires on the front, you are going to die,” he said. “The absolutism of this is astounding to me.”
(The following information is on South Bend, Ind.-based online and mail order tire and wheel marketer Tire Rack's website, offered as advice to consumers when buying sets of tires:
“When tires are replaced in pairs…the new tires should always be installed on the rear axle and the partially worn tires moved to the front. New tires on the rear axle help the driver more easily maintain control on wet roads since deeper treaded tires are better at resisting hydroplaning.
“If the front tires have significantly less tread depth than the rear tires, the front tires will begin to hydroplane and lose traction on wet roads before the rear tires. While this will cause the vehicle to understeer—the vehicle wants to continue driving straight ahead—understeer is relatively easy to control because releasing the gas pedal will slow the vehicle and help the driver maintain control.
“However, if the front tires have significantly more tread depth than the rear tires, the rear tires will begin to hydroplane and lose traction on wet roads before the fronts. This will cause the vehicle to oversteer—the vehicle will want to spin. Oversteer is far more difficult to control and in addition to the initial distress felt when the rear of the car starts sliding, quickly releasing the gas pedal in an attempt to slow down may actually make it more difficult for the driver to regain control, possibly causing a complete spinout.”)
Mr. Baldwin said that along with what he called the inflexible “new-tires-on-rear” policy is a “no-rotation” policy if newer tires are on the rear.
“One company put out a memo last month stating that you can't rotate your tires if there is more than 4/32-inch difference in tread depth between the axles,” he noted.
No one has taken a hard look at the “new-tires-in-rear” policy since the 1970s, he claimed, noting that “these things get into an emotional debate. We ought to back them up with cold, hard facts.”
There are about 240 million passenger vehicles on U.S. roads. “The average age of those vehicles is 10.8 years, which means half of them are older than 10.8 years,” he said.
The average age of a tire at replacement is 3.7 years, and about 40 percent of the time a motorist buys either one or two tires, Mr. Baldwin said.
“Millions and millions of vehicles carry more tread in front than in back. If you look at a parking lot, you will not find a single vehicle with four of the same tires,” he added, though he did not address or seem to take into account vehicles still running on OE tires or those vehicles whose owners have replaced their tires recently.
Using figures from the National Highway Traffic Safety Administration (NHTSA) and interpolating from the rules of straight probability, Mr. Baldwin said the minimum number of vehicles in the U.S. with at least 9/32 inch of tread on the front and 4/32 or less in back is 8.8 million.
“You'd think there would be a heck of a lot of accidents because of this, based on the videos,” he said. “From NHTSA accident statistics, we should be able to pick out what's going on with new-on-rear vs. new-on-front.”
Yet a statistical analysis of NHTSA data did not indicate an increase in accidents when new tires were on the front of vehicles, Mr. Baldwin said.
He also showed videos of his own vehicle testing, using tires of different makes, models and tread depths.
“The results showed that the lowest tread depth, regardless of position, dictated where vehicle control was lost—except for shaved tires,” he said. “In videos, that fact is generally left out. Shaved tires with 5/32 inch tread depth behave like a 2/32-inch worn tire.”
At the end of his speech, Mr. Baldwin cited an article that appeared in the Feb. 27, 2012, issue of Tire Business and the March 5, 2012, issue of its Akron-based sister publication Rubber & Plastics News.
The article concerned a tire aging bill before the Maryland House of Delegates—a bill Mr. Baldwin told the Clemson audience he opposed—and a Feb. 21 hearing on the legislation.
At that hearing, the bill's sponsor cited the recommendations of Ford and other auto makers that tires be removed after six years.
The RMA testified that Ford's testing covered only tires it retrieved in the catastrophic Ford Explorer-Firestone recall of 2000.
“The problem is, that isn't true,” Mr. Baldwin said of the RMA's testimony. “You hurt the credibility of your organization when you lie about the research of others.” (Editor's note: Miles Moore is the author of the article on the Maryland tire aging bill.)
Interviewed after his speech, Mr. Baldwin told Tire Business that Ford did test Firestone tires collected from the recall for the effects of aging. But, to ensure the validity of the testing, the vehicle maker also performed the same tests on tires made by other manufacturers that were specified as original equipment on the Explorer.
“The results of the tests were consistent,” he said. “Tires deteriorate as they age.”
An RMA spokesman said the association stood by its Maryland testimony.