Continuing its campaign to relax government regulations affecting the automobile industry, the Reagan administration yesterday unveiled a proposal to eliminate a three-year-old rule that requires tire manufacturers to give consumers more information about the durability of their product.

The National Highway Traffic Safety Administration said yesterday that it wants to suspend a key provision of the 1979 rule that had been in the making for 12 years and that requires tire manufacturers to test and label their products to let consumers know the expected life of the treads of passenger-car tires.

The NHTSA said test results do not portray the performance of a tire accurately and thus hurt consumers rather than help them because they are misleading.

Manufacturers have to test and rate tires according to their treadwear, traction and temperature resistance. An "A" represents a good performance, while a "C" is the poorest rating.

According to NHTSA Administrator Raymond A. Peck, the same test conducted on the same brand of tire often produces results that would change the grade.

"The treadwear portion of the uniform tire quality grading system is not merely failing in its primary purpose, to inform consumers, it may, in fact, be positively misleading consumers through government-sanctioned grades," Peck said. "This means consumers could be paying more for a tire that will, in fact, provide only the same or inferior treadwear performance as another, cheaper tire."

What's more, the tests cost manufacturers roughly $10 million a year--a sum which is passed on to consumers, Peck noted.

As a result, Peck wants to do away with the treadwear-rating requirement, but maintain the traction and temperature ratings. Meanwhile, NHTSA would undertake to come up with a better treadwear test, he said.

Consumer groups immediately denounced the proposal. "Instead of throwing out the baby with the bath, they just threw out the baby," said Clarence M. Ditlow, director of the Center for Auto Safety. Although Ditlow acknowleged that the treadwear-rating tests could be improved, he said that the current tests are better than no tests at all, which is what consumers would have if the requirement is eliminated.