These vehicles with a steel tube spaceframed chassis, either home constructed or professionally built, divided into three Classes by the application of an engine capacity and / or engine type limit.
These 'Specials' are specifically designed to be strongly built enough to withstand a collision or roll over, but are not fitted with bumper bars as deliberate contact is definately not allowed.
Modifications allowed: unlimited, the engine / gearbox / transaxle / axle types are free according to each Class cc limit and specification. Specials are fitted with a multitude of engine types with 1.0 / 1.1 / 1.3 motorcycle / 1.3 / 1.4 DOHC engines / 1.8 / 2.0 SOHC & DOHC engines / 2.1 / 2.5 DOHC engines / 2.8 / 3.0 / V6 / 3.5 / 4.0 / 5.0 and V8 engines, mainly mid or rear mounted to Hewland / Renault / VW gearbox or direct drive.
All of the Specials Classes are very popular with both spectators and drivers alike.. Many are geared to acheive in excess of 100mph! Now that, on a 400m track, isn't slow!
Special rule book on the NASA website