They're big, clunky and most of the time not driven very fast, but farm tires require no less technology than their passenger, light truck and commercial truck tire counterparts.
``These tires need to be technically as sound as any tire,'' said Al Clark, manager of ag and forestry engineering and tire testing for the Firestone Agricultural Tire Division, a subsidiary of Bridgestone/Firestone. ``It's very critical to take care of these products.''
Mr. Clark and several Firestone Ag executives stressed these points to about 40 tire dealers and farmers gathered July 15 at the Firestone Test Center in Columbiana for a program about how the company tests farm tires, the technology that goes into making them and the importance of proper inflation.
Although it has held such programs before, this was the first time in five years the company had invited farmers and dealers to see first-hand what goes into the development and testing of its farm, forestry and skid steer tires, said Michael Bogunia, national sales manager for Firestone Ag, which has its headquarters in Des Moines, Iowa.
Located in rural Columbiana, just south of Youngstown, Ohio, the center is the world's only testing facility dedicated to agricultural tires. It sits on 350 bucolic acres not far from the family farm of Firestone Tire & Rubber Co. founder Harvey Firestone, who is credited with putting the farm on pneumatic tires back in the 1930s.
While the site itself looks peaceful and restful, the work at the center is anything but. Tire endurance testing runs 24 hours a day, five days a week, with an unmanned tractor, tethered to a pole, pulling a drag unit continuously around a concrete oval. A similar test on another of the center's five circular tracks measures the cutting and chipping tires experience on sharp slag pavement.
The center also performs drum tests 365 days a year to determine tire en-durance and resistance to weathering. Other tests look at bar tear, rim slip, the effects of tread design on vibrations levels, spring rate, traction, fuel economy and road wear.
``We want to find out the weakness of every tire that we make,'' said Mr. Clark, who also manages the Columbiana test center.
With farms growing larger and farmers working fields often miles apart, the tire maker is actively testing the performance of farm tires running at speeds of up to 40 mph.
``What we're concerned about when you're on the highway is what would happen if you have to make a panic stop, or if you have to make a very rapid lane change,'' Mr. Clark said. ``What does that vehicle do? What happens to the tires? Do the tires help you or hurt you?''
Like the company does with its other types of tires, Firestone Ag uses computer modeling to develop and design its farm tires.
``We're going to find a way to predict tire performance before ever making a tire,'' Mr. Clark said.
With faster speeds in mind, the company is working on developing cooler-running farm tires with higher strength levels. ``They've got to be stronger because of the fact that we're going to be going faster,'' he said.
Ride comfort is another area that's gaining importance, as farmers drive their tractors over longer distances and at higher speeds.
``It's not too far in the future that large tires on tractors will be noise treated,'' Mr. Clark said. ``That would be a first.''
To get the optimum performance out of a tractor, tires play a major part, said Len Wagner, manager of field engineering at Firestone Ag in Des Moines. Most horsepower is lost through the tires, he explained, noting that proper inflation can improve a tractor's performance by as much as 25 percent. ``Tires have more to do with tractor performance than any other single item on the tractor with the exception of the engine,'' he said.
To properly set up a tractor, Mr. Wagner outlined five steps:
c Determine the proper weight of the tractor.
c Determine the front-to-rear axle weight split.
c Determine the amount of weight on each tire.
c Recommend the correct tire.
c Match the inflation to the load.
``Before you leave, I want each of you farmers to know what your tractor should be-not necessarily what it is-for proper set up,'' Mr. Wagner told the group.
Tire dealers and farmers who attended the program said they were impressed with what they saw and heard.
``No one ever told us how to compute horsepower for the right tire size and inflation pressure,'' said Jim Rosen, who along with his brother Bob owns C.C. Rosen & Sons Inc., a tire dealership with outlets in Mt. Crawford and New Market, Va.
Attending the session has ``been worth it,'' added Bob Rosen. ``Just seeing the steps (Firestone) takes to test tires, and that they do all this, gives you a lot of confidence in the product.''
Lee Ratliff, who's raising 30 beef cattle on 137 acres and owns South Branch Tire in Petersburg, W.Va., also didn't realize tire pressure was so critical in farm tires.
In a rear farm tire, ``I put 18 pounds of air in it regardless,'' he said.
But while he said he understands the value of proper tire inflation pressure to tractor performance, Mr. Ratliff also appreciates the difficulties of frequently changing air pressures based on how a tractor is being used.
``Hardly anyone is running a tractor the same way for a long period of time,'' he said. ``Using 18 pounds (of pressure) will not hurt you one way or the other.''
Still, he said he was impressed to learn how much inflation pressure impacts performance.
``I will pay more attention to this,'' he said.