The Alfa Romeo 155 first joined the BTCC in 1994 following relatively successful seasons in both the Italian and French championships. Alfa was keen to take the BTCC title in its first season, but a poor result at the end of season World Cup made the team realise that the 155 would need a helping hand if it was to beat the highly competitive BTCC field. Over the winter break, Alfa Romeo designed and built a new 'Silverstone' version of the 155 which sported a new rear wing and adjustable front spoiler. Both these aerodynamic devices added little to the cars performance on the road, but on the track it would give them the traction and braking advantage they were looking for.

The cars themselves are built by Alfa Corse (Italian for Alfa Racing) in Turin, using standard pressed steel production body shells taken from their production line at Pomigliano, near Naples. Initial chassis preparation is handled by local Turin company Albatech, who also assisted with the technical design of the cars, and so good is their work that the 155 comes in a full 40kgs below the minimum weight limit.

To achieve this, Albatech remove all unessisary mountings and brackets before seam welding the stress areas and adding a tubular steel roll-cage, which extends to support the front and rear suspension pick-up points. All this work not only produces a light car, but also one that is twice as stiff as the road going version.

With the chassis complete, the engine and drive train are then added. Unlike the road cars, the race engine is not based on the 2 litre twinspark varient, but rather a rally proven in-line 4 which has also been used in Abarth's Fiat Tipo F3 cars. The basic iron block is from the 164 model, while the head is the taken from the 155 Q4 turbo but rotated through 180 degrees.