Kevin Bacon's bicycle is a single-speed '84 Raleigh Competition. While no differentiation is made in the film, at least three different configurations are seen on Bacon's bike during the movie: Fixed-gear, single-speed, and outfitted with 0-degree trick forks during various scenes in Bacon's apartment. A possible freewheel is suggested early in the film when Bacon dismounts while in motion and a distinct clicking sound is heard until the bike stops moving.
As Jack enters the trading floor he takes a stack of trading slips from Chip's hands. A few moments later, his hands are empty and Chip hands him some trading slips again.
When Jack is twirling his bike's handlebars and wheel in his apartment the down-tubes on the front forks are straight, but the on his street bike the down-tubes have a slight forward bend at the axle.