Gary Stevens and Chris McCarron are both successful professional jockeys, both having won the Kentucky Derby and Breeder's Cup races. McCarron retired a couple months before accepting the role of Charles Kurtsinger.
Over 40 horses are featured in the film, with 10 sharing the role of Seabiscuit. The horses' running distances never exceeded three furlongs, or three eighths of a mile, per take.
Although the film leaves unexplained Riddle's demand that the War Admiral-Seabiscuit match race not use a starting gate, he did have an actual reason: War Admiral loathed starting gates.
Most of the audience at the Pimlico Race with War Admiral were blow-up mannequins with masks as faces, long sleeve T-Shirts with painted on suits, and plastic hats (which were provided to all of the unpaid extras).
The movie never mentions that Seabiscuit and War Admiral were related. Seabiscuit's sire Hard Tack was sired by the great Man o' War as well as War Admiral.
A contraption called Equicizer was used to film the close-up action. It resembled a hobby horse. It was a mechanical horse that had springs, a wooden head and a carpet body. It was affectionately called SS Seabiscuit. In reality, it was a 12 ft by 20 ft rolling platform with a steering wheel in the rear and front. It simulated the rolling action of a running horse and yet it ran on rails around the track. It was powered by a 454 Chevy engine and could go at a speed of 40-50 mph.
The Seabiscuit/War Admiral race originally held at Pimlico race track was actually filmed on location at Keeneland race track in Lexington, Kentucky. The track, as well as some of the surrounding area, had to take on some minor cosmetic changes in order to accurately reflect the time period.
Although the film doesn't mention it Seabiscuit and War Admiral were supposed to race in June of 1938 in the Massachusetts Handicap. Seabiscuit was scratched due to "fevered legs". War Admiral finished 4th marking the first time he finished out of the money.
In the scenes filmed at Santa Anita racetrack you can see a statue of a horse by the paddock. This statue is a memorial to Seabiscuit that exists at Santa Anita. Another statue stands approximately 100 yards away; this is a tribute to George Woolf, Gary Stevens' character in the film.
The 35mm prints of this film come from a digitally grain reduced digital intermediate. As a result they are littered with grain reduction artifacts from start to finish.
Ex-racing driver Allen Padelford specially designed the MTV insert cars - a Mobile Technocrane Vehicle to allow filmmakers to shoot insert shots for horse race sequences. It run up to 45 mph and weighs at 28 thousand pounds. The car can fit a 30ft Technocrane dolly at the back and Wescam XR head at front. Another one was designed specifically two fit in two animatronic horses.
While the movie describes War Admiral as being a huge horse close to eighteen hands tall, the real-life War Admiral was well known for being one of the smallest sons of Man o' War. War Admiral was actually the same size as Seabiscuit, which was approximately fifteen hands tall.
When trainers and jockeys refer to a horse having "a great heart" or "a noble heart," they do not mean courage, as we would say about a human. They mean that it has a competitive nature. A horse that has more stamina than speed would also be described as having a great heart (though perhaps more often in steeple-chasing than in flat racing).
When trainer Tom Smith tries to bring a goat into Seabiscuit's stall, he is absolutely right in saying that many horses feel better if they have company. (Most mammals who live with humans do.) It has been a fairly common practice to partner a horse with a goat in a stall. It is also alleged that the saying "to get one's goat" came from the practice of stealing a goat from a rival race horse's stall the night before a big race, so that the horse would be upset. This etymology is possible but has never been fully supported. (That a horse would neatly kick a goat out of its stall is, of course, fanciful.)
When Red Pollard tells George Woolf how to ride Seabiscuit, he says, "Show him the stick at the quarter pole, and he'll give you a whole new gear." To show the stick means to bring the whip, or crop, up close to the horse's eye, on one side, with the suggestion that the next move might be a whipping along the flank. The crop is not meant to hurt the horse, only to say, "Okay, NOW is the time to really move!" Many horses run faster if slapped; others simply freeze and stop running. To show the stick, then, is only a suggestion, and it will make most horses shift into higher gear, if they still have energy left to run for the win. (And animal lovers should note: the horse crop is not used to hurt the horse, only to excite it with adrenaline or (worst case) fear. A jockey who draws blood is likely to be penalized up to the point of losing his or her license, which means no more employment.)
Jockey Red Pollard is shown to keep his weight down by starving to 115 pounds. This was because Seabiscuit, when young and already small, had to run in what are called handicap races. The "handicap" is an added weight that is assigned to each horse according to its past races and its predicted ability to run against horses who weigh more or less than it does. Professional jockeys will starve themselves so that their horse will carry as little weight as possible: that is: their own weight plus the lead weights which are laid into the saddle of the running horses. Red Pollard, at 5'7", raced against professionals who were 5'3" - but professional jockeys will do almost anything if they love racing enough and are daring enough to risk their bodies.