NASHVILLE—No tire or wheel is perfectly round, which means even ``balanced'' tire-wheel assemblies can harbor hidden vibrations caused by flexing in the sidewall and tire and rim runout. Now, for the first time in the aftermarket, Hunter Engineering Co. is offering a balancer it claims automatically diagnoses vibration problems—including radial force variation and lateral and radial rim runout—and provides easy-to-follow instructions on how to solve them.
Tire dealers and retreaders attending the recent World International Tire and Rubber Association Expo got a firsthand look at the machine, which Hunter displayed on the trade-show floor.
Using a ``road roller'' that applies up to 700 pounds of pressure against the tire assembly, the GSP 9700 wheel balancer is ``capable of seeing what the road sees,'' said Sean Latham, Hunter's Louisville, Ky.-area sales representative.
It gives the user the ability to ``OEM match'' a tire and wheel and to solve non-balance-related vibration problems. ``No other machine does that,''he said.
The GSP 9700 features Hunter's exclusive Road Force Measurement System, which simulates a road force test and measures uniformity in the tire-wheel assembly, including radial force variation—the amount of change in stiffness in the sidewall and footprint when the tire is under load.
By locating the lowest spot on the rim and the stiffest spot on the tire under load, you can make the assembly round, Mr. Latham said. ``This is called OEM matching,'' he said, a process previously done only by new-car manufacturers using ``uniformity graders'' costing as much as a million dollars.
Hunter is selling its GSP 9700 for $9,500, which is about double the cost of other balancers.
``By owning this machine, you can separate yourself from the competition,'' Mr. Latham said. Dealers can and should charge for this service, he added.
Some dealers have expressed concern that the GSP 9700 may reject a large number of tires as defective. Mr. Latham responded that ``a tire manufacturer would prefer to have one tire come back that's bad with proof compared to four without proof.''
He added: ``If customers expect a new-car ride and feel, then they should at least have the opportunity to have the process done.''
Besides radial force variation and runout, the machine also can determine vibration problems resulting from an improperly seated bead and excessive balancer mounting error.
The unit also provides for precision wheel balancing using split weights. Hunter said the Servo Stop wheel-positioning feature positions the rim for exact placement of adhesive weights.
All of the major tire makers have endorsed the GSP 9700, Mr. Latham said, as have General Motors Corp. and Daimler-Chrysler A.G., which recommend the machine for analyzing and solving vibration problems.
``With this machine you will have the confidence to repair or diagnose any wheel and/or tire vibration problem,'' he said.