Australian-born Auckland physicist Graeme Putt also believes Phar Lap won the richest race in the world with an injured hoof which caused him to falter as he entered the turn into the final straight.
He said lateral forces on his split hoof caused him pain and he slowed in the Agua Caliente Handicap in Mexico in 1932.
He lost the clear lead he established but once he came out of the turn and into the straight the lateral force came off his hoof and he "streeted" ahead to win by about two lengths.
Dr Putt's book, Phar Lap the Untold Story, would be launched formally in Timaru next week when a life-sized statue of the horse is unveiled at the Timaru racecourse.
The statue by Auckland sculptor Joanne Sullivan-Gessler of Phar Lap in full stretch showed his enormous stride and racing style.
Dr Putt said when Phar Lap went to America he was fitted with the wrong horseshoes which broke one of his hooves.
He said the broken hoof made Phar Lap's win in Mexico even more remarkable.
Since Phar Lap died in April 1932, theories about what caused his death have abounded, including deliberate or accidental arsenic poisoning, and one that he ate grass from a nearby paddock which had been sprayed with weedkiller.
Dr Putt, however, said he probably died from a bacterial infection, anterior enteritis, and showed no symptoms to suggest arsenic poisoning.
"The jury really is still out completely on it."
Had it been anterior enteritis it would have been an agonising death from an internal bloating.
"It was agonising, no doubt about that."
In his book, Dr Putt also said Phar Lap's trainer, Australian Harry Telford, learnt most of his horsemanship skills in New Zealand after moving to this country when he was about a year old. He returned to Australia when he was in his 30s.
"That is something which is not properly recognised.
"It is a real Anzac story with Australia and New Zealand oozing into it."
He said about half the book was about Phar Lap's life in New Zealand until he was sold as a yearling and taken to Australia.
The rest of the book was divided between his life in Australia when he became famous and his trip to America for his final race in Mexico in 1932.
"The Americans love him and they voted him among their top 10 most loved horses, which included Trigger, Roy Rogers' horse, Silver, the Lone Ranger's, and characters like that as well as Secretary and Man O' War.
"This is on the strength of one race (the Agua Caliente Handicap). He won it in such sensational circumstances and it is indelibly imprinted on American turf law.
"Two minutes on the track. I call it a moment which became an eternity," he said.
