The wheels on Metro's subway cars are wearing out almost twice as fast as was anticipated, and wear on some sections of rail has been excessive, the Metro board was told yesterday.

Immediately after board members were given the bad news on that subject, they directed the Metro staff to prepare a detailed study of another, more visible problem: those "out of service" Farecard machines and regularly uncooperative entrance and exit gates.

Ralph L. Wood, director of rail operations for Metro, said the wheels on Metro's cars were expected to run for 300,000 miles, but experience has shown that 250,000 miles is optimal. But even that target is not being met. "We are currently averaging 150,000 miles per transit car wheel," Wood said.

"In addition tot he wheel-wear factor on the high (outboard) rail in curves has been excessive, as well as the wear of the rail at switch points and cross-overs."

Metro, said the wheels on Metro's cars were expected to run for 300,000 miles, but experience has shown that 250,000 miles is optimal. But even that target is not being met. "We are currently averaging 150,000 miles per transit car wheel," Wood said.

"In addition to the wheel-wear situation," Wood said, "the wear factor on the high (outboard) rail in curves has been excessive, as well as the wear of the rail at switch points and cross-overs."

Metro has not had to replace a large number of wheels on its 300 subway cars or any significant sections of track. However, Wood said, a special item will have to be included in next year's Metro budget to pay for excessive rail and wheel wear.

Furthermore, Wood said, some new track-laying contracts have been revised to change track design because of inordinate wear experienced "in certain areas," including the Farragut North and National Airport stations.

Such modifications, called change orders, inevitably result in cost overruns on construction contracts. Wood said he had no estimate on how much money that would be.

Safety is not at issue in the rail and track wear problems, Wood said in response to a reporter's question.

In a highly technical memorandum to the board, Wood listed several possible reasons for the excessive wear on both wheels and rail, including Metro's 1/4 inch tighter-than-usual width between rails and trucks that resist turning on curves. A truck is the collection of four wheels - two on each rail - on each end of the subway cars.

It is also possible, the memorandum said, that Metro's combination of track angle and wheel tread "could be a significant factor in the unusual or excessive wheel and rail wear." That would be a design flaw, not a construction contract problem.

Metro is investigating the rail wear to determine if any action against contractors is warranted, according to John S. Egbert, assistant general manager for design and construction; none have been taken.

A consultant is studying the Metro operation to recommend ways of reducing wheel and rail wear, Wood said.

Cleatus E. Barnett, Metro board member from Montgomery County, raised the Farecard issue after the results of a study conducted by the Washington Suburban Transit Commission (WSTC) indicated a problem.

In that study, consisting of 31 random checks of the vending machines at the Silver Spring Metro station during a 10-day period, WSTC's Gloria Fischer never found all the vending machines in operating condition. On 28 of the checks, two or more of the nine vending machines were out of service. On one occasion - an evening rush hour - seven of the nine did not work.

"We are nearing the end of the warranty on a lot of those machines," Barnett said, "and the performance has fallen far short."

Metro recently complained vigorously to Cubic Western Data, the manufacturer and maintainer of the Farecard equipment, and Cubic responded by firing 12 employes of its maintenance subcontractor.