Concern over the quality of rubber from Asian mills has caused multinational companies to "blacklist" some of the millers and tighten quality control in U.S. tire plants.

The background for the concern is the government-negotiated recall of Firestone's 500-series of radial tires, at a likely cost to the company of $134 million.

The Singapore buyer for one U.S. multinational company keeps newspaper artcles about Firestone tacked up on his office wall to show Asian millers and rubber salesmen who visit his office.

Firestone has never revealed the reasons for the failure of some of its 500-series of high-performance radials. Industry insiders say the evidence seems to point to poor design rather than flaws in the compounds.

Firestone's problems, however, have made all the companies more sensitive than ever about the quality of the natural rubber they use in their complex tire compounds.

The lowest-performance U.S. tires still contain about one-quarter natural rubber. Heavy duty aircraft tires and tractor tires are made almost completely from natural rubber.

In the last two years, the U.S. tire companies have stopped buying Standard Indonesian Rubber-50, the lowest grade.

"The shippers in the Far East just loaded this grade up with all the junk they had," said Dim Scheuer, president of the New York City rubber trading firm Internatio. "It became useless for tire production."

Scheuer said he thought the worst quality problems had been ironed out.

Nevertheless, one knowledgeable Akron company source complained that the "quality of rubber from Asian mills has continually deteriorated. They're putting in hard-to-detect materials. But we're to blame for not being tougher and more selective."

On Jan. 1, Malaysia began introducing new grading standards to help U.S. tire companies gauge the behavior of the rubber in the final, crucial state of tire manufacturing.

In this final stage, the tire is put into a mold that resembles a waffle iron and is heated for several minutes. This process of vulcanization "curesc the tire and makes it virtually impervious to heat and cold. But the time required in the mold can vary depending on the characteristics of the natural rubber, such as its geographical origin and the kind of trees it came from.

This is not now indicated by the suppliers, even though improper vulcanizing can cause weak spots and tire failure.