Williams and Force India became the first Formula One teams to take the covers off their cars for 2015, revealing Wednesday the most significant design change from last season: a new front.
Technical regulations in F1 have been remained stable except for the requirement to change the nose of the cars, which will make them more pleasing on the eye this season.
''It is a redesign that involved a lot of work over the winter,'' Force India technical director Andrew Green said at the team's launch in Mexico - the home country of one of its drivers, Sergio Perez. ''The new regulations caused a loss in terms of downforce and we've been working to claw back all that performance.''
Williams' chief technical officer Pat Symonds said the change in regulations ''offered us a slight headache,'' adding: ''The new front bulkhead and nose geometry had much more of an impact than we had initially anticipated, and the effect on the aero was profound.''
Williams had the worst campaign in its history in 2013 - scoring just five points - but fought back last year under drivers Valtteri Bottas and Felipe Massa to place third behind champion Mercedes and Red Bull in the constructors' championship. That was Williams' highest finish since 2003.
''I hope as a team we are more capable of maintaining the forward momentum to catch Mercedes, than the teams behind us are of catching us,'' Symonds said.
Force India's new car, which will be driven by Perez and Nico Hulkenberg, has different livery - black and silver, with streaks of orange.
''We've added silver,'' team principal Vijay Mallya said, ''because I think it makes it look more mean, more hungry.''
Force India scored a team-record 155 points last season and was sixth in constructors' standings.
''We've a really solid foundation,'' said Hulkenberg, who outscored Perez 96 points to 59. ''I'm now looking forward to us improving, taking the next step.''