IF YOU are trying to persuade an adolescent shortstop to buy your brand of after-shave lotion, tell him Carl Yastrzemski, Pete Rose and Joe Morgan are so enchanted with your product that they all sing its praises on television. Athletes and product endorsements are as quintessentially basic to American advertising as perfume commercials between Thanksgiving and Christmas.

The Lake Placid Olympic Organizing Committee imaginatively concluded that, it athletes can endorse products for payment, then athletic events can do the same thing, only on a much bigger scale than a Yaz or a Reggie. That is probably why you are dimly aware that somebody or other makes the official tire for the 1980 winter Olympics at Lake Placid. (That somebody is Goodyear and please give them a break, because the Olympic endorsement probably cost more than their blimp.)

Together, the state of New York and the federal government agreed to underwrite almst $100 million of the projected $140 million to $150 million worth of expenses involved in holding the 1980 winter Olympics at Lake Placid. The $46.7 million tab for the administrative expenses -- salaries, phones, lodging -- was left to the Lake Placid Olympic Organizing Committee. And that's where the endorsements come in. As of last accounting on Sept. 30, the product endorsements had helped to raise $34.2 million of the total.

In addition to an official tire, there are, appropriately, an official automobile, an official motor oil and even an official snow plow if any or all of the above do not perform to official standards.

What else do Olympic athletes need to compete for a gold medal in the winter games? You think we have made it up but here's a list of some of the items: official Olympic thermal underwear to keep warm, official Olympic contact lenses to see better, official Olympic cold remedies to feel better, and official Olympic mattresses to sleep better. Probably only gold-medal winners should allow themselves a glass of Schlitz, the official Olympic domestic beer (or if they want to go uptown, a glass of Kirn, the official non-domestic Olympic beer). Kellogg's will be the real 1980 official Olympic breakfast of champions and runners-up; 150,000 individual boxes of its cereals helped Kellogg's win that designation. On top of that cereal, even those who taste the agony of defeat will probably feel better with a few slices from the eight tons of official Olympic bananas from Chiquita. If hunger persists, there are 20,000 pounds of official Olympic spaghetti from Muellers. And 5,000 gallons of official Olympic Maxwell House coffee to wash it all down. If all this leaves you with a mild headache, just take a couple of official Olympic Excedrin.

Next February, when we are all rooting for our American amateurs against those steroid-stuffed, government-subsidized East Germans, it will help us to remember that isn't just freedom crossing the finish line, but free-(burp)-enterprose as well.