The styrofoam model was used to create a steel "test frame", which had to stand up to several standards: have a speed of over , go from 0 to in 5 seconds, possess a steering system to make sharp turns at city corners, and withstand a self-propelled launch of up to . On the first jump test, the Tumbler's front end collapsed and had to be completely rebuilt. The basic configuration of the newly designed Tumbler included a 5.7-liter Chevy V8 engine, a truck axle for the rear axle, front tires by Hoosier (which are actually dirt racing tires used on the right rear of open wheel sprint cars), 4 rear 44/18.5-16.5 Interco Super Swamper TSL tires (44" tall, 18.5" wide, mounted on a 16.5" wheel) and the suspension system of Baja racing trucks. The design and development process took nine months and cost several million dollars. With the design process complete, four street-ready race cars were constructed, with each vehicle possessing 65 panels and costing $250,000 to build. Two of the four cars were specialized versions. One version was the flap version, which had hydraulics and flaps to detail the close-up shots where the vehicle propelled itself through the air. The other version was the jet version, in which an actual jet engine was mounted onto the vehicle, fueled by six propane tanks. The visibility inside the vehicle was poor, so monitors were connected to cameras on the vehicle body. The professional drivers for the Tumblers practiced driving the vehicles for six months before they drove on the streets of Chicago for the film's scenes. The interior of the Tumbler was an immobile studio set and not actually the interior of a street-capable Tumbler. The cockpit was oversized to fit cameras for scenes filmed in the Tumbler interior. In addition, another version of the Tumbler was a miniature model that was 1:6 scale of the actual Tumbler. This miniature model had an electric motor and was used to show the Tumbler flying across ravines and between buildings. However, the actual Tumbler was used for the waterfall sequence. The filmmakers intended to create a very mobile Batsuit that would allow the wearer to move easily to fight and crouch. Previous film incarnations of the Batsuit had been stiff and especially restrictive of full head movement. Costume designer Lindy Hemming and her crew worked on the Batsuit at an FX workshop codenamed "Cape Town", a secured compound located at Shepperton Studios in London.