Spectacular Bid's quest for the Triple Crown will not culminate with a quiet, routine coronation ceremony. Instead of being the formality that his trainer and jockey expect, the Belmont Stakes will probably be his toughest race of the year.

The challenge to the champion will come from Coastal, who was practically unknown three weeks ago when Spectacular Bid was winning the Preakness in awesome fashion. But he will be a solid second choice in the wagering Saturday, and the first choice of handicappers who place absolute faith in the importance of time.

Coastal had shown flashes of ability in an abbreviated campaign last year, but after suffering an eye injury he did not return to competition until late April. He won races at six and seven furlongs before trainer David Whitely entered him in the 1 1/8-mile Peter Pan Stakes.

Coastal was sensational. He annihilated his nondescript opposition by 13 lengths and was timed in 1:47 over a track that was not especially fast. Students of the arcane science of speed handicapping would say that he ran faster than Spectacular Bid did in either the Kentucky Derby or the preakness.

His form reminds many New Yorkers of Stage Door Johnny, the late bloomer who tipped his sharp form in the Peter Pan Stakes and then wrecked Forward Pass's Triple Crown aspirations in the 1968 Belmont.

But while Stage Door Johnny provides a precedent that such a lightly raced colt can win the Belmont, there is plenty of contradictory evidence that says Coastal does not have enough experience. Horses need rigorous conditioning to win at 1 1/2 miles, and Coastal - who has never even raced around two turns - may find himself at a serious disadvantage.

Whiteley knows this. He and owner William Haggin Perry agonized for days over whether to make Coastal a supplementary nominee to the Belmont. Even today, he was saying he was not sure that the colt would run. Whiteley learned his craft from his father, Frank, whose hallmark as a trainer was his refusal to ask too much too soon of his horses. David Whiteley knows that Coastal should have one or two more weeks more preparation. "If he had had just one more mile-and-one-eighth race, I wouldn't hesitate a minute," he said.

Because he lacks the experience and the fitness of Spectacular Bid, Coastal probably cannot win the Belmont if the favorite runs his best race. But it is conceivable that Bid will not be as overpowering here as he was in Louisville and Baltimore.

The rigors of the Triple Crown series wear out many horses by the time of the Belmont Stakes, and Spectacular Bid's training for this race has not provided unequivocal evidence that he is in peak condition. Before all of his other races this spring, Bid worked so fast that he left no doubt about his sharpness. However, his major work for the Belmont was a mile in 1:39 last Sunday, a time that seemed unexpectional.

Trainer Bud Delp thought otherwise."It was sensational work," the trainer insisted earlier this week. "The track was very sticky, and it was probably as good a work as he's ever had. I figure that 1:39 was like 1:36 on a normal track. He's perfect."

Spectacular Bid seemed to confirm Delp's assessment when he sped three-eighths of a mile in 34 1/5 seconds in his final tune-up this morning. "He's never been better," the trainer said.

If Delp is correct, Coastal will not be able to beat Spectacular Bid.And none of the other eight horses in the Belmont lineup will be close to him.

Golden Act and Screen King ran creditably to finish second and third in the Preakness, but they gave no reason to believe that they can turn the tables on Spectacular Bid. The only other horse in the field who might be a factor is General Assembly, who finished second in the Kentucky Derby before a poor performance in the Preakness.

Angel Cordero Jr. rides General Assembly, and he could provide more trouble for Spectacular Bid than any of his equine rivals. Cordero's long-simmering feud with Bid's rider, Ron Franklin, exploded in a fight here on Wednesday.

However, today they shook hands after being lectured by the stewards at Belmont Park. ut Spectacular Bid has already proved he is good enough to overcome his jockey's shortcomings. His experience and conditioning should enable him to overcome Coastal and capture the Triple Crown. The order of finish, in an unexpectedly close Belmont, should be: Spectacular Bid, Coastal, Golden Act.