8.2. Only steel bodied dampers are permitted. 8.3. Gas, remote reservoir or double adjustable dampers are not permitted. 8.4. Independent suspension is not permitted.
9. Front Axle 9.1. Historic Class Vehicles must be fitted with the front axle beam from an Austin 7 or Ford Sidevalve. 9.2. Post Historic Class Vehicles must be fitted with a steel front axle beam of period design.
10. Steering 10.1. Cars in the Historic Class must use a period steering box. 10.2. The position of the two swivel axles must not vary whilst steering. 10.3. Four-wheel steering is not permitted.
11. Rear Axle 11.1. Vehicles must use a live rear axle from a period series production car.
12. Transmission 12.1. Vehicles must be equipped with a differential gear which divides torque equally between the driving wheels.
12.2. Vehicles must not use any locked or lockable torque biasing or limited slip differentials or any other automatic device which is designed to achieve the same result.
12.3. Any clutch / torque converter attached to the engine flywheel must be bolted directly to the engine crankshaft. 12.4. Gearboxes and transmissions with a sequential shift are prohibited.
13. Brakes 13.1. Disc brakes are not permitted. 13.2. Vehicles must be fitted with operative and effective front and rear brakes.
13.3. Independent rear braking is permitted but no self-compensating controls are permitted on the rear brakes which must be single leading-shoe drum brakes.
14. Wheels and Tyres 14.1. Tyre security devices are permitted in the rims. 14.2. Wheels must not carry any chains, spikes or non-skid attachments.
14.3. Vehicles must carry one spare only which must be a driven wheel as fitted on the car fitted with any permitted tyre
14.4. It is not permitted to add Ballast to the spare wheel. 14.5. Motorcycle tyres on non-driving wheels are permitted. Minimum tyre pressure 2psi.
14.6. In Historic Class a control tyre specified in the Official Documents must be used on the driven wheels. Front wheels must bolt onto the brake / hub.
14.7. In Post Historic the rear wheels rims must not exceed a width of 11.43cm( 4.5in) measured between the bead flanges nor a diameter of 15in.
14.8. Tyres must be of a maximum size 165mm x 15in on driving wheels and must be selected from Ch. 8 App. 4 Tyre List 3 or previous lists.
Motorsport UK National Competition Rules 2026 Edition 1
Chapter 17 Appendix 6- Technical Regulations- HST Formula 634