As any tire dealer knows, tires have as much personality as the vehicles they carry. They may all look the same, but each tire has a different composition or ``DNA'' that begins to take shape when a vehicle manufacturer comes up with a concept for a new vehicle.
``We know about the vehicle before the original equipment tire maker does, and we have pre-conceived notions of what we want the vehicle to be,'' said Art Anderson, chief engineer on the Chrysler Crossfire at DaimlerChrysler A.G.
``But it's not just a set of specifications you write down and hand to the tire maker,'' he said. ``You have a rough starting point they try to match as closely as they can.''
The tire standards development process typically takes two to three years and is fairly similar at all of the car makers, but it hasn't always been that way, said Bill Vandewater, consumer products manager in sales engineering for Bridgestone/Firestone.
The Japanese vehicle makers work more closely with their suppliers, while the U.S. and European manufacturers have had a history of more or less trying to dictate their tire performance requirements, he said.
``But they're working much more closely with us now than they were seven, eight, 10 years ago,'' sometimes inviting tire makers into the vehicle design process ``when it's still a white piece of paper,'' Mr. Vandewater said.
The Japanese car makers are known for being more collaborative than their North American and European peers, but they are no less prescriptive.
Toyota Motor Corp. uses benchmarking data on more than 600 tires of all sizes from its suppliers as a starting point for setting its final targets, said Darrel Sterzinger, an engineer at Toyota Technical Center U.S.A. Inc. ``Basically, we set the standards, but we will discuss the feasibility of the standards with the suppliers.''
Honda of America Manufacturing Inc.'s tire performance standards are set by its homeland parent company, but Toyota's North American technical center sets the targets for its U.S.-produced vehicles, Mr. Sterzinger said.
``It's not a situation where they (car makers) are dictating to us,'' said Robert Arguelles, chief engineer of electronic brake systems at Continental Teves North America. ``It's very much collaborative throughout the development process.''
The process of setting tire performance specifications begins with a list of requirements from the domestic car companies. These cover ``every performance property you could possibly think of, from electrical resistivity to treadwear, traction, fuel economy and weight-pages of specifications,'' said Raymond J. Labuda, vice president of tire technology at Hankook Tire Co. Ltd.'s Akron Technical Center.
The most critical specifications are either regulatory or safety-related, said Deepak Parekh, supervisor of tire and wheel standards at Ford Motor Co. ``We try to tune the tire and the rest of the vehicle based on what segment we are competing in, but certainly safety and regulatory requirements must be met.''
It's the tire makers' responsibility to meet Federal Motor Vehicle Safety Standards, said Dave Wood, tire engineering manager for General Motors Corp.'s Tire-Wheel Systems Group. Those standards revolve around lab or high-speed endurance, bead retention, tire dimensions and most recently, the low-pressure performance requirements that stem from the TREAD Act. GM also adds in its own set of performance requirements ``that go above and beyond that,'' Mr. Wood said.
Customer satisfaction types of issues, which include tire wear and vehicle pull drift, are next in importance, Mr. Parekh said, followed lastly by convenience factors like valve stem orientation.
For something like the ride of the vehicle, there are no specific ratings, said Andreas Gerstenberger, vice president of sales and marketing at Continental Tire's P/LT replacement tire business unit. It can be defined by numerous things including how a vehicle performs in severe maneuvers, how comfortable the ride is, whether it drives straightforward and how noisy the tires are.
Customer satisfaction issues differ from vehicle to vehicle, Mr. Parekh said. ``Trade-offs are a reality when talking about tire performance.''
In any vehicle you have to make trade-offs in ride and handling, comfort and load capability, those involved in the process said.
Rolling resistance, for example, is typically very important in mainstream vehicles for its contribution to improved fuel efficiency, Mr. Vandewater said. ``But if it isn't mainstream, maybe handling is more important for the target audience.''
Tire and vehicle manufacturer engineers refer to a so-called ``spider diagram'' when discussing tire performance standards. The performance aspects at any given point on the web-like diagram are affected when you try to pull out or improve them in another area.
``Usually, when you make an improvement in one area, it has to come in (or get worse) in another area, unless you can get to a breakthrough,'' Mr. Vandewater said.
That's where the discussions between tire and car makers begin, he said. ``They understand that if they want improvements in one area, they're going to have to make sacrifices in another.''
When the car and tire makers get together to compare notes, the tire suppliers ``can tell us if we've gone overboard,'' Mr. Wood said. ``The suppliers have the opportunity to supply us input, commentary and criticism, and we take that into account.''
But each of the standards categories has a goal that the tire has to meet, GM's Mr. Wood said. Some of those are the same across vehicle applications, like standard endurance, but others, like rolling resistance, are specific to each vehicle.
``When you get a rolling resistance spec, you either meet it or you don't,'' Mr. Labuda said. ``But when it comes to ride and handling, and we're talking about a system, we work very closely with them on that.''
``If we get a number of suppliers telling us what we're asking for is technically unfeasible in the time we have asked, we take that into account,'' Mr. Wood said.
Ford also said it takes tire maker recommendations under consideration. ``Then it goes out for bid, and the tires must meet all of the specifications,'' Mr. Parekh said.
The car makers are still ``stretching'' the web, he said, ``But that's good-it forces us to develop some of these new technologies that we can then take to the replacement market.''
Car maker specifications are exceedingly tough to meet, said Guy Edington, managing director of Kumho Tire Co.'s North American Technical Center in Akron. ``I've sat in a number of those meetings thinking to myself, `It can't be done-we don't have the technology to meet those specifications.' So you come up with new compounds, new constructions, etc. You invent ways to meet those specifications.''
Tire makers have been able to make the spider web charts larger over the last 10 years, Mr. Wood said, through new compounds, constructions, tread designs and mold shapes.
There is give and take as trade-offs are negotiated, said John Hagan, manager of OE tires at Pirelli Tire North America. ``But I'm finding as we pick up more programs, they're really keeping us on target,'' he said.
Pirelli gained its first North American OE business with Ford last fall. Now it has new business it has yet to announce with DaimlerChrysler A.G. and General Motors Corp., he said.
At the beginning of the process, ``They'll listen to us,'' Mr. Hagan said. ``They may not agree with us, but it becomes a negotiating process.''
Both sides can make changes, Mr. Anderson said. For example, if the vehicle's tires need to have a really stiff sidewall, the car company can cut back on the damping to make the ride more comfortable. ``But with the Z-rated tire on the Crossfire, it was really important to us to not give up any of the performance attributes of the car,'' while still having really good snow and ice performance.
After a tire maker is sourced a contract, it still needs to adhere to the list of specifications, Mr. Wood said. ``But occasionally, a vehicle program will change direction; we'll decide a vehicle should be a little less handling-oriented and a little more ride-oriented.''
Once specifications are agreed upon-and in Ford's case, signed off by both the tire and car maker-the development process is ``completely hand-in-hand after that, until the tire is approved for the vehicle,'' Mr. Gerstenberger said.
Ms. Begin, based in Detroit, writes for Rubber & Plastics News, a sister publication of Tire Business. Free-lance writer Chuck Slaybaugh contributed to this article.