The Firestone Tire & Rubber Co. has failed to notify the "great majority" of its customers of the recall of its defective 500 steel belted radials, leaving millions of Americans driving on "life-threatening, defective tires," the Carter administration told Congress yesterday.

Joan Claybrook, of the National Highway Traffic Safety Administration told the consumer protection subcommittee of the House Commerce Committee only about 15 percent of the estimated 8.7 million defective radials have been replaced as of March 31. She said the "great majority" of the tire owners had yet to be notified of the recall agreement, which was announced six months ago.

The recall was negotiated between Firestone and NHTSA after the government determined that the tire had a "safety-related defect" which caused it to blow out, or in some other way to fail, to huge numbers. NHTSA pointed to dozens of deaths and injuries due to tire failures as justification to pull them off the road.

In addition to the 8.7 million tires to be replaced free 500,000 other tires have been recalled under a half-price adjustment program for tires that did not qualify for the free replacement.

Claybrook contended that Firestone has only notified about 1.2 million consumers - who own about 40 percent of the tires in question - about the recall.

She said her agency still receives many complaints from Firestone tire owners about the tires and the recall.

Claybrook called on Firestone to speed up the recall. "With the high mileage summer months nearly upon us," she said, "it is vitally important that Firestone replace those recalled tires as quickly as possible. The major purpose of the recall is to get these defective tires off the road before they cause more accidents, deaths and injuries."

For its part, Firestone contended in a statement released after the hearing, "we are running ahead of the recall rate we agreed on with NHTSA. To date we have replaced nearly 2.8 million tires," the company contended.

In addition, Firestone said it has sent out 75 percent of the notification letters it agreed to ship, and continues to produce 400,000 extra tires each month to meet the recall.

But Clarence Ditlow, director of the Center for Auto Safety - the consumer group that first called for a recall of the tires - said "we knew this would happen. We are still receiving hundreds of consumer complaints that NHTSA should be checking out, but isn't."

"It's a shame, but Firestone is probably laughing all the way to the bank," Ditlow added.

Firestone earlier this week reported sharply increased earnings. The company earned 57 cents a share, or $32.6 million in profits (on sales of $1.23 billion) during the quarter ending April 30, and $1.17 a share or $67 million (on sales of $2.56 billion) for the six-month period ending on the same date.

Last year, the company showed huge losses in both periods, on smaller sales. The losses were attributed to a $110 million write-off the company took to cover the cost of the recall.

Claybrook was testifying for proposed legislation that would force tiremakers to give the public media notice of tire defects.

"There is nothing to stop NHTSA from publishing that notice on its own," said Ditlow, who was critical of NHTSA's handling of the whole recall. "I don't care if they have the power to order advertising or not, the important thing is tell the public."