Production began without a finished script; scenes were often written the day of filming. During one driving sequence, Tom Cruise actually had to read his lines off cue cards attached to his windshield, which resulted in a minor car accident. For subsequent driving sequences, Cruise was fitted with a special earpiece to have lines fed to him.
The scene where Cole leaves the pits after a race, to hit Russ Wheeler, is based on an actual event during the 1987 All-Star race at Charlotte, North Carolina, between drivers Bill Elliott and Dale Earnhardt.
The man who drove for Harry Hogge, prior to Cole, was named Buddy Bretherton. In the movie, they mention he died hitting the wall at Daytona. Harry also mentions that Buddy heard voices while driving. Buddy Bretherton is probably based on NASCAR driver Bobby Isaac, who drove for crew chief Harry Hyde. Issac claimed to have heard voices telling him to get out of the race car or he would die. So he pulled the car off the track and quit. Isaac died several years later from a heart attack, while driving in a 1977 Late Model Sportsman race at Hickory Motor Speedway with 25 laps left.
Some footage for the movie was shot during the 1990 Daytona 500. Two additional cars, driven by Bobby Hamilton and Tommy Ellis, were added to the rear of the field for the express purpose of shooting them for this film. They were not officially scored, and left the racetrack after one hundred miles (forty laps) were completed. At one point in the race, leader Dale Earnhardt even lapped the movie cars.
According to an article in Car and Driver by Bob Zeller, Bobby Hamilton was paid 14,000-15,000 dollars by Rick Hendrick to drive the camera car. At the time, Hamilton was making about 185 dollars a week driving a wrecker (tow truck). He did so well, that Hendrick hired him on for the next NASCAR race in Phoenix, and the rest of the season.
All cars used in the movie for the races had to pass inspection and qualify. Bobby Hamilton qualified one of the movie cars in the top ten; they removed the cameras and he was allowed to enter the race.
Tom Cruise and Robert Duvall characters are (very) loosely based on former driver Tim Richmond and his crew chief Harry Hyde. Richmond was known as an overnight sensation, and Hyde was the veteran crew chief. The scene where Duvall's character teaches Cruise about tire management is based on an actual incident between Hyde and Richmond, who died of AIDS complications the year before the film was released.
NASCAR driver Greg Sacks did most of Tom Cruise's stunt driving. Cruise wanted to do his own stunt driving, but wasn't allowed to for insurance reasons. The Chevrolets were prepared by Rick Hendrick's racing team, which later used some of the movie cars in real races. 35 cars were wrecked during filming.
In an effort to give a more realistic atmosphere, professional racing broadcasters were brought in to play the broadcast reporters and track announcers. Key among these were members of ESPN's racing crew, including booth announcer Bob Jenkins, and pit reporter Dr. Jerry Punch.
Most of the cars used in this film were actually Chevrolets outfitted with special fiberglass bodies made to resemble stock cars. The vehicles routinely broke down from the strain of the racing or had their bodies greatly damaged. At one point, half the fleet was in the repair shop.
Real-life Hendrick Motorsports pit crew member Mike Slattery served as an extra for Cole's crew. After hearing what the stuntmen's pay would be, he asked for the opportunity to do some of the stunts. However, when he saw how close the car came to the stuntmen, he changed his mind saying, "They can have it!"
Don Simpson, Jerry Bruckheimer, and sometimes Robert Towne, often started their days on set having arguments with Tony Scott over how to shoot scenes. Meanwhile, the crew sat around getting paid, sometimes for twenty hours a day. Some later said that they had made so much overtime on the film, that they could have gone on vacation for four full months after the wrap date.
Despite the budget overruns and delays, reportedly, it was only after shooting was finished that the filmmakers discovered they had neglected to film Cole Trickle's car crossing the finish line at Daytona.
Quentin Tarantino said the film was his favorite big budget racing movie: "Yeah, yeah, you laugh, but seriously, I'm a big fan. To me Days of Thunder is the movie Grand Prix (1966) and Le Mans (1971) should have been. Sure, it had a big budget, big stars and a big director in Tony Scott, but it had the fun of those early AIP movies. I just don't think it works if you take the whole thing too seriously".
When Cole tells Harry "when it comes to the car I'll take your word," he is referring to a line from a deleted scene where he states, "I'll take your word for what a car can do but I'm not taking anybody's word for what I can do." The line can still be heard in the trailer.
In Daytona, Don Simpson and Jerry Bruckheimer spent 400,000 dollars to have a vacant storefront in their hotel converted into their private gym, with a large neon sign reading "Days of Thunder." Simpson also kept a closet full of Donna Karan dresses to offer the attractive women his assistants found on the beach, and held private parties with friends like rapper Tone Loc. They threw a special welcome party for the crew at a local nightclub with minimal food,and drink, and no music, but plenty of hookers they flew in, most of whom they limited to a roped-off VIP area with themselves and Tom Cruise.
Cars designed specifically for the movie officially raced at Phoenix and Darlington, with Greg Sacks driving Cole Trickle's City Chevrolet in both races. Bobby Hamilton drove Rowdy Burns' Exxon car at Phoenix, while Hut Stricklin drove it at Darlington. None of the cars finished their races, but Hamilton did lead his race for five laps before an engine failure.
In another scene, Trickle is told he can not pit because the crew is too busy eating ice cream. This incident actually occurred at the 1987 Southern 500 involving the Hendrick Motorsports #35 team with crew chief Harry Hyde and Richmond's replacement driver Benny Parsons.
Due to internal conflicts, the said wrap date kept getting pushed back. At one point the production schedule was revised three times in a single day, leading the unit production manager (the studio's on-set financial liaison) to confront Don Simpson and Jerry Bruckheimer. In response, they told him "Screw the schedule." It went from February 1990 to the end of May, severely jeopardizing its chances of making its expected summer release date (it came out a month later). Unsurprisingly, the budget almost doubled over this wasted time too, requiring that the movie make a then-astronomical 100 million dollars merely to break even.
The scene where Cole and Rowdy destroy a pair of rental cars by racing them through the city streets loosely referenced early 1950s NASCAR superstars Joe Weatherly and Curtis Turner, each of whom were known to rent cars, race, and crash them with abandon.
During the Darlington race in which the two movie cars appeared in, Neil Bonnett, one of the drivers interviewed at Daytona before the race, was nearly killed in a serious accident. Ironically, Bonnett was killed in a crash during a practice at Daytona in 1994.
In the beginning of the film, the announcer introduces driver Aldo Bennedetti from Reading, Pennsylvania. This character is most likely a reference to real-life driver Mario Andretti. Both are of Italian descent, Mario's brother is named Aldo, and Mario is from Nazareth, Pennsylvania.
Robert Towne had a barn built to his specifications while the production was filming outside Charlotte. He didn't like it, and they didn't use it. When the crew moved down to Daytona for scenes there, another barn was built. Towne didn't like it either, and most of the barn scenes he had envisioned were thus dropped from the script.
On July 3, 2013, NASCAR driver Kurt Busch ran a City Chevrolet inspired paint scheme at Daytona International Speedway. Also that same year, the original car and Kurt's paint scheme, were added to the Lights Camera NASCAR exhibit in Charlotte, North Carolina.
The cars used as those of Cole Trickle, Rowdy Burns, and Russ Wheeler were provided by Hendrick Motorsports, with racers Greg Sacks, Bobby Hamilton, and Hut Stricklin as the stand-in drivers. In order to provide authentic race footage involving the cars, these cars were actually raced on three occasions. In late 1989, Hamilton and Sacks raced at Phoenix. Bobby Hamilton officially qualified fifth, and led a lap before his engine blew. In 1990, the cars were raced again at Daytona and Darlington. Greg Sacks drove a car during the Busch Clash, while Sacks and Hamilton drove unscored entries in the Daytona 500. At Darlington, Hut Stricklin and Greg Sacks drove two of the cars, but both were pulled from the race early, after Sacks broke a crankshaft.
Development of the movie started in 1987, first with writer Warren Skaaren, then Donald Stewart and then Warren Skaaren again. Finally, producers decided to hire Robert Towne, who wrote the final version of the script.
The film's theme song "Last Note of Freedom" was sung by David Coverdale of the band Whitesnake at the request of Tom Cruise himself. Coverdale's vocal parts were recorded in 1990 in Los Angeles during a day off of the Whitesnake Slip of the Tongue Liquor and Poker world tour.
Even though this is the first collaboration between Tony Scott and composer Hans Zimmer, it could have been their second and maybe even third movie. Scott wanted Zimmer to score his previous films Beverly Hills Cop II (1987) and Revenge (1990), but since Zimmer was more or less an unknown in Hollywood at that time, the producers instead went with more known composers.
This was the first of an ongoing list of films in which Hans Zimmer would compose the score for a Jerry Bruckheimer production. An official score album was not released until 2013, by La-La Land Records.