IT IS THE impossible question, but when you get Ron Turcotte on the phone, it has to be asked. Which one of Secretariat's Triple Crown races was best?

"They were all great," Turcotte said last week from his home in Canada.

In fact, a very strong case can be made that the same horse ran the greatest Derby, greatest Preakness and greatest Belmont, all in one 5-week period.

As Big Brown, after totally dominating the other horses in the Derby and Preakness, gears up for the Saturday's Belmont Stakes and a run at the elusive Triple Crown, it is hard not to think of the horse who during that 5-week stretch was the greatest race horse who ever lived.

Affirmed was the toughest (and last) horse to win the Triple Crown, in 1978. Alydar made him run all the way.

Secretariat? That horse was never running against the competition. Secretariat was running against himself and the clock. The 1973 Triple Crown winner won both ways.

Each of the three races was glorious. And won in a completely different way.

Secretariat came from the back of the pack in the Derby, running each quarter-mile faster than the previous one and setting a track record that still stands.

Secretariat looped the field on the first turn of the Preakness, making the greatest move in the history of Pimlico, and set another track record, which was missed by the teletimer but not by anybody with a stopwatch.

Secretariat broke running in the Belmont Stakes and never slowed down, breaking the world record for a mile-and-a-half and winning by 100 yards.

Turcotte, 67, can't say which one was the greatest. He does say he is proudest of the Preakness because he had to make a split-second decision after the leader went the first quarter-mile in a very slow 25 seconds.

"I let my horse drop back," Turcotte remembered. "When I went to drop in, they started backing up into me. I said, 'I don't want to get trapped here.' So I just breezed by them."

All of them. On the first turn. In a few hundred yards.

Sham, Secretariat's foil in the Derby, took up the chase on the backstretch, starting 2 1/2 lengths behind and finishing 2 1/2 lengths behind.

"I could have won by 10," Turcotte said. "If I really asked him to run, I don't how far he would have won by."

Winning by far would have to wait 3 weeks.

"I didn't have any intention of taking the lead [in the Belmont]," Turcotte said.

But Secretariat did.

And Turcotte knew one thing about his horse: If he wanted to run, you let him run.

Sham was lapped right outside Secretariat as they roared down the backstretch together.

"I knew we were going fast, but we were going faster than I thought," Turcotte said.

Sham started to disappear on the far turn. On CBS, Chic Anderson conjured his "tremendous machine." Horse and rider entered the stretch alone.

There are pictures of Turcotte looking around in the stretch, apparently trying to see where the opposition was. He was not looking for other horses. He was looking at the toteboard, trying to find the teletimer. He was curious, too. How fast was he going?

"By the call, I knew I was way in front," Turcotte said. "When you're alone like that, you can hear.

"I glanced back when the first of the three odds boards were coming up. And there is a timer on every one of them."

Turcotte saw the half-mile (46.2 seconds), three-quarters of a mile (1:09.8) and mile (1:34.2) times. He knew that he had been running into a headwind on the backstretch. The horse ran right through the wind and Turcotte remembered thinking, "Oh my God, we're flying."

He caught the second odds board and the time for a mile-and-a-quarter flashed by (1:59). It was faster than the final time of the Derby.

Just about everybody who has seen that famous photo of Turcotte looking around at the wire assumed he was looking for other horses. He wasn't. He was looking for the third odds board. He wanted to see the final time. It froze at 2:24.

When Turcotte pulled up, one of the outriders said, "I always knew you had a clock in your head, how fast do you think you went?"

Turcotte said: "2:24."

"How did you know you went in 2:24?"

He looked.

And he wasn't really surprised. In the final days before the Belmont, Secretariat had morphed into an animal who was no longer of this world.

Turcotte remembered going out to dinner with Secretariat's trainer, Lucien Laurin, and saying: " 'If this horse gets beat, I'm going to hang up my tack.' That's how confident I was."

The winning margin was 31 lengths. Secretariat had become the first Triple Crown winner in 25 years. And, as long as they run the series, any TC winner or any winner of any of the races will have to be measured against what Secretariat did on two May Saturdays and one in June.

In all three races, Secretariat loyalists were wondering what exactly Turcotte was doing. He was too far back in the Derby, made a giant move on the first turn in the Preakness and was going too fast too soon in the Belmont. Secretariat ran through all notions of what was supposed to be.

Turcotte watches all the big races. He expects to be at Belmont Park Saturday. He counts himself a Big Brown fan, but . . .

"I'm not sure how he'd do against last year's crop," Turcotte said. "I'd like to see him win it, but I don't know if he can do it."

If Big Brown does win, the horse will enter a very exclusive club.

Regardless of how fast, how far and what finishes behind him, that is forever.

And then there is Secretariat, the horse who went to forever and kept on going. *