rFactor is a computer racing simulator designed with the ability to run any type of four-wheeled vehicle from street cars to open wheel cars of any era. rFactor aims to be the most accurate race simulator ever, providing advanced tyre modeling, complex aerodynamics and a 15 degrees of freedom physics engine.

rFactor has a detailed interface during offline race sessions or online games, allowing players to control the mechanical setup of their cars, chat to other players, and enter the racing arena in their vehicle. rFactor is a significant evolution of F1 Challenge '99-'02, but without the licensing of Formula One circuits and teams.

There has been active amateur development of F1 Challenge, with season updates put out for the 2003 and 2004 seasons, an amateur ETCC touring car mod, and a commercial GT mod. rFactor is highly extensible and modifiable.

The essential aim of the rFactor physics engine is to bring together vehicles with circuits. It does provide an advanced tyre model, claiming to be much better than the Pacejka model previously used in most simulators. rFactor's tyre model simulates the tyre use cycle according to temperature and wear.

In the first review of rFactor, published on AutoSimSport, Jon Denton says:
"What the tyre model in rFactor does very well is that it models the relationship between slip angle, self aligning torque and cornering force - and it does this better than anything that has come before."