a.
b.
c.
In Classes B-D Bodywork ahead of and below the centre line of the front wheels and behind and below the centre line of the rear wheels may be removed.
Panels to the front and rear of the centre line of the front and rear wheels respectively may be replaced by panels from any model in the same family of cars.
In Classes B-D the weight distribution of the Vehicle may be altered by the addition of Ballast which must be positioned within the body shell or bumpers firmly secured and not visible or protruding.
d. |
Ballast must not be varied during an Event. |
e. |
The fitting of sump chassis and exhaust under-body guards is permitted. |
f. |
External mirrors may be removed. |
4.2. |
In particular Vehicles must: |
a. |
Be equipped with an effective windscreen or aero-type screen. |
b.
c.
The body overhang of non-production cars must not exceed one-fifth of the overall car length at the front and one- third at the rear. Overhang is measured from the line of the road wheel centres.
For production cars any extensions must not exceed the overhang proportions of a non-production car. Any additional spare wheel carrier should be fitted as close as possible to the body. Production cars need not comply with Ch. 7 App. 2 Art. 6 in respect of bonnets.
4.3. With the exception of cars of periods A to D all cars must be equipped on all wheels with mudguards which present no sharp edges and cover the complete wheel( flange + rim + tyre) around an arc of 120 degrees. This minimum coverage must:
a.
b. c. be achieved with a continuous surface of rigid material. The rear tyre must not be visible when viewed from above
extend forward ahead of the axle line extend downward behind the wheel d. extend downward behind the driven wheel to a point no more than 150mm above the axle centre line.
4.4. Vehicles must be equipped with two fixed seats for Driver and Passenger the rearmost part of which must not be behind the rear wheel axis.
5. Engine 5.1. Engine tuning is permitted within the following limitations:
a.
b.
c.
The cylinder head and block must remain as originally supplied by the manufacturer as standard for that model.
If the Class structure suggested in Arts. 1.1 – 1.6 above is used then except for Classes B and C the carburettors and inlet and exhaust manifolds must remain as originally supplied by the manufacturer as standard for that model.
Fuel injection and / or forced induction are prohibited unless offered by the manufacturer as standard or optional equipment for that model.
d. Stroke of the crankshaft may not be altered. e. Cylinders may be re-bored to a maximum of + 0.060in.
5.2. If forced induction is used, the coefficient will be 1.4:1
Motorsport UK National Competition Rules 2026 Edition 1
Chapter 17 Appendix 4- Technical Regulations- Car Trials Formula 624