Saab is one of a handful of carmakers looking to buck the trend of building bigger and heavier cars with each new model generation, the carmaker confirming at this week’s London Motor Show that future models will be more compact. Starting with the upcoming 9-1, due to arrive in 2012, engineers have decided to drop a lower-medium architecture planned for the car and replace it with General Motors’ global Gamma small car platform.

The information comes from the boss of General Motors Europe, Carl-Peter Forster, who explained to Automotive News that Saab doesn’t want its future models to grow in size.

The story is the same for the next-generation Saab 9-3, due in early 2010. Saab originally planned to use the new Ypsilon-2 architecture, used in cars like the Opel Insignia and upcoming production Buick Invicta, but has since decided to use the lower-medium Delta architecture.

Saab’s managing director Jan-Ake Jonsson confirmed Forster’s statements, telling reporters that Saab wants to break the industry trend that successors to existing models automatically get bigger. Another carmaker that’s been very active in downsizing its models and reducing vehicle weight is Mazda, which expects to replace its entire lineup with smaller and lighter vehicle architectures by 2011.

Pictured above is the Saab 9X BioHybrid Concept, which previews the upcoming 9-1 compact car.

2008 Saab 9X BioHybrid Concept