Technical Regulations

The following technical regulations cover vehicles which are to be used for RTV and Modified trials. The regulations are taken from the current Motor Sports Association year book (Blue Book) and all competitors are advised to obtain a copy of the Blue Book which details all of the regulations covering Motor Sport in the United Kingdom.

Modified trials vehicles taking part in trials held wholly on private property need not be registered, taxed or fitted with a speedometer. Vehicles competing in RTV trials should be taxed and have a valid MOT.

All vehicles must comply with the following regulations:-

  1. Chassis
    1. Have a protective bulkhead of non-flammable material between the engine and driver/passenger compartment capable of preventing the passage of fluid or flame in the case of fire. All gaps/holes must be sealed with GRP, intumescent putty or other non-flammable sealant. Magnesium is prohibited for bulkheads.
    2. Have a complete floor of adequate strength rigidly supported within the driver and passenger compartment. No gaps or holes should be visible.
    3. Have a minimum wheelbase of 1270mm (50 inches
  2. Body
    1. Be fitted with bodywork that includes a crew compartment effectively isolated from the engine, batteries, gearbox, transmission shafts, brakes, road wheels, operating linkages and attachments, petrol tanks, oil tanks, water header tanks, brake reservoirs, catch tanks and radiators.
    2. Be fitted with doors of bodywork giving side protection to the driver and passenger. These should comply with the side waistline requirement as detailed in section 3 (seating)
    3. Have a bonnet of casing of metal or solid non-flammable material covering and surrounding the main engine structure which is secured by fasteners of adequate strength and have a positive locking action. All moving parts of the engine must be covered.
    4. Be fitted with bodywork of sufficient internal size to comply with regulations 2vi and 3i below.
    5. Not have the space normally occupied by the passengers encroached upon but may have the passenger seats removed.
    6. Have bodywork providing a minimum transverse cockpit opening width of 810mm. This width may not be interrupted.
    7. Be equipped on all wheels with mudguards which present no sharp edges and cover the full width of the tyre around an arc of 120 degrees. This must be achieved with a continuous surface of rigid material with no gaps, slots, holes or vents. It must extent forward ahead of the axle line and downward behind the wheel to the centre line of the axle.
  3. Seating
    1. Have a normal adequate seat within the driver/passenger compartment. The seat must be rigidly located within the compartment and for Modified vehicles must not tilt, hinge or fold. It must retain the driver within the vehicle. The rear most part of any seat must not be more than 380mm behind the rear wheel axis. The seat cushion when uncompressed must not be less than 150mm below the top edge of the adjacent body side or door. Other seats which are fitted must similarly comply.
    2. Modified vehicles should have head restraints fitted to prevent the drivers head going backwards on impact.
  4. Engines
    1. Be equipped with a positive method of throttle linkage closing in the event of a linkage failure by means of an additional external spring to each throttle spindle.
    2. No vehicle may draw induction air for within the driver and passenger compartment. Air intakes must either be forward of the front bulkhead/windscreen of piped through to the rear of the vehicle to draw outside air from behind the rear bulkhead. The air pipe must be of non-flammable of flame retardant and fuel resistant material and must be securely located.
    3. The choice of size and make of engine is free in all trials classes.
  5. Suspension
    1. Be fitted with sprung suspension between the wheels and the chassis unless originally manufactured otherwise.
    2. The choice of spring and damper supplier is free. In RTV classes lifted springs may be fitted but they must use the original manufactures mounting points. In RTV classes dampers must use the original manufacturers mounting points.
    3. Suspension and steering movement must be controlled to avoid fouling of wheels and tyres on chassis or bodywork.
  6. Brakes
    1. Be fitted with brakes that are operative and capable of stopping and holding the vehicle as required. A foot operated single pedal brake system should be used to achieve this.
    2. Independently operated front or rear brakes are permitted in modified class one trials vehicles to act as fiddle brakes. They are not permitted in modified class Two, or RTV trials vehicles.
    3. A separate hand brake system must be fitted to all vehicles.
  7. Steering
    1. Have a full circumference full diameter steering wheel unless originally manufactured otherwise.
    2. Have steering movement controlled to avoid fouling of wheels and tyres on chassis or bodywork.
    3. Have steering lock assemblies removed on all modified trials vehicles.
    4. RTV trials vehicles must have the steering wheel and the steered wheels directly connected by a mechanical link.
    5. The fitment of a power assisted steering system is permitted in all trials classes. Lock stops on front axles must be in place in RTV classes, in Open and Mod classes they may be removed as long as the requirements of 7ii. are complied with.
    6. It is permitted to extend the steering drop arm in Modified classes however this is a component which is under tremendous stress whilst in use therefore it is essential to carry out this conversion to the best engineering standards.
  8. Wheels
    Except in the case of vehicles originally manufactured without wheels all vehicles shall comply with the following.
    1. Have not less than four road wheels and tyres (excluding the spare).
    2. Not be fitted with any wheel spacers exceeding 25mm in thickness.

Not be fitted with duplicated driving wheels unless originally manufactured otherwise or unless permitted by supplementary regulations. Reversing of standard and altered road wheels within the RTV classes is prohibited

  1. Tyres
    1. Be fitted with wheels and tyres that are compatible and also acceptable to the organiser. A particular type and size of tyre may be prohibited by the ASRs. The use of dumper-type, open-centered or very aggressive tread pattern tyres is be prohibited in RTV and Modified trials at certain venues (for example Military venues). In all RTV and Open classes hand cutting of tyres is strictly forbidden. RTV class vehicles are not permitted to run dumper tyre, open-centered or very aggressive tread pattern.
    2. A spare wheel need not be carried.
    3. Modified class vehicles may have more than four wheels and tyres.
    4. All tyres used on any event must comply with the minimum DOT requirements on depth of tread.
    5. The use of tyre chains and studded tyres by competitors is prohibited.
    6. Tyres should be covered by the mudguards or body work to cover the whole width of the treaded area.
  2. Cooling
    1. Have any fluid lines or tubes or internally/externally metal braided hydraulic pressure hoses carrying coolants through the driver and passenger compartment enclosed in a solid metal cover and insulated and isolated to prevent the occupants of the vehicle touching the hot surfaces. Such lines or tubes or coverings must be painted red.
    2. All open radiators, expansion bottles whether front or rear mounted, must be covered in such a manner that nobody can burn themselves on the hot open/unprotected areas of the radiator. Special attention should be made to protect occupants from hot water from an exploding radiator.
  3. Transmission
    1. Have the transmission outside the driver and passenger compartment, beneath the floor or secured in casings or covering of solid material.
    2. Be equipped with an operable reverse gear.
    3. The use of limited slip, torque biasing, or locking differentials is permitted in Modified class 1,2 and RTR Class 6. Modified vehicles may have their diff’s welded or pegged permanently locked. Classes 3,4 & 5 RYV vehicles may only have diff locks or limited slip diffs if it was a production fitment for that particular vehicle.
    4. Vehicles may have traction from tracks if produced in that manner.
    5. Vehicles with automatic transmissions shall have a starter inhibiting switch allowing it to start in park and/or neutral only.
  4. Oil Systems
    1. Have any oil lines passing through the driver/passenger compartment protected, and if non-metallic enclosed in internally/ externally metal braided hydraulic pressure hose.
    2. Oil coolers, filters and cooling water expansion tanks must not be fitted in a position where, if burst, the hot fluid can come into contact with the occupants of the vehicle.
  5. Fuel Systems
    1. Have any fuel lines passing through the driver/ passenger compartment protected, and if non-metallic or pressure lines, enclosed in internally/externally metal braided hydraulic pressure hose.
    2. If fitted with fuel fillers in the boot, or under closure, have collector/ spill trays incorporated to enable spillage to drain outside the vehicle.
    3. Use normally available pump fuel. The use of fuel additives, octane boosters, or AVGAS (aviation fuel) is prohibited.
    4. If using LPG, conform with the Construction and Use Regulations, and also the LPG Industry Technical Association Code of Practice No.11.
    5. Have tank fillers and caps which do not protrude beyond the bodywork, nor are situated within the driver/passenger compartment. The caps must have an efficient locking action to reduce the risk of accidental opening during an accident and ensure closing after refueling. Air vents must be at least 250mm to the rear of the cockpit. All fuel caps should be of the sealed type to prevent spillage.
    6. It is strongly recommended that the fuel tank is covered with an outer steel container which acts as a second line of defense in the event of a roll over.
  6. Electrical Systems
    1. Have any batteries in driver/passenger compartment enclosed in a leak proof container and securely located. Such batteries must be duly protected to prevent leakage of acid and spillage onto the occupants of the vehicle in the event of a rollover.
    2. Have battery terminals which are protected from any metal contact which could result in a short circuit.
    3. Be equipped with battery, generator and self-starter. RTV vehicles are required to be fitted with operative sidelights, tail lights, brake lights and headlights.
    4. Headlights on modified vehicles (Class 1 and 2) will be required in all night events.
    5. Have the battery earth lead, if not readily distinguishable, identified by a yellow marker.
    6. Be fitted with suppressors as required by the Wireless Telegraphy Regulations.
    7. Modified (Class 1 and 2) vehicles must be equipped with a circuit breaker. This must isolate the battery from all electrical circuits and must cut the engine at the same time. The switch location is optional, but its operation must be possible from both inside and outside the vehicle. The circuit breaker control(s) must be identified by a red spark on a white edged blue triangle. If a diesel engine is fitted with an electric stop it must be connected to the circuit breaker. If it is a pull cable stop system a second cable must be fitted next to the isolator switch and marked clearly “pull to stop engine” on a plate 75mm x 50mm white background with red lettering.
  7. Towing Points and Recovery Rope
    1. All vehicles must be equipped with towing points front and rear. The tow ball or point must be bolted using suitable nuts and bolts of adequate size. These must accept a rope loop and be secure without requiring the use of shackles or other such attachments. On Modified vehicles where a tow-ball is used, it must be fitted so as to retain the rope, i.e. it should either be mounted with the ball facing away from the direction of pull, or, where it is mounted close to a chassis member, a trap should be formed to prevent the rope from coming accidentally detached.
    2. Be equipped with a nylon rope of a minimum 25mm diameter. This rope must have a closed loop at each end and be of at least 4.5 metres in length. The use of chain or wire bond is prohibited. Polypropylene or hemp ropes are not advisable. N.B. Marshals may use any equipment approved by the Clerk of the Course
  8. Exhaust System
    1. Have the exhaust system isolated from the driver/passenger compartment (e.g. beneath the floor or secured in casings of solid material).
    2. Trials vehicles may have front mounted exhaust. Hot surfaces must be covered or shielded with suitable material.
    3. Have no part of the exhaust system protruding laterally beyond a plane through the outer track of the front and rear wheels, or to the rear of the bodywork more than 150 mm.
    4. If all enveloping body is fitted, have supplementary protection for exhaust systems that protrude outside the bodywork.
    5. All exhaust outlets to be not more than 610mm from the ground and face to the rear and downwards
  9. Silencing
    1. In all events, conform to a maximum permitted noise level as laid down in the current MSA ‘Blue book’. The requirement as listed in the 1999 MSA blue book is a Max of 100db at 0.5m with the engine at 2/3 maximum revs. Continuous noise testing will take place during events and competitors will be advised of excessive noise. WARNING: Temporary silencers, bypass pipes and the inclusion of temporary parts to achieve silencing requirements are prohibited. Officials may refuse to carry out noise checks on vehicles utilizing temporary parts in exhaust systems. Please refer to section E of the current MSA Yearbook. Measurements to be taken at 4500 rpm max (or two thirds throttle opening if no tachometer fitted or diesel engine) with engine at normal working temperature.
  10. Windscreens and Side screens
    1. If fitted to have windscreens of either laminated glass or plastic, of a minimum thickness of 4mm (except RTV Trials Vehicles). Plastic side screens, where fitted, should also have a minimum thickness of 4mm unless fitted otherwise by the original manufacturer.
    2. The use of mesh or net hinged sidescreens on open vehicles to retain the limbs of driver and passenger in the event of a roll-over is advised. The use of a sun roof with glass is not permitted in Modified vehicles where it should be replaced with a metal panel.
  11. Roll Over Protection/Roll Cages
    Aluminum alloy roll over bars and roll cages are banned in all forms of motorsport where a roll cage is required to be fitted. The use of roll cages is advised for all events. Full roll cages as per drawing 2 below are mandatory in Modified (Class 1 and 2) classes.
    1. General Considerations
      1. The basic purpose of the roll over bar is to protect the driver/passenger if the vehicle turns over or is involved in a serious accident. This purpose should not be forgotten, and in consideration of this, all roll bars and roll cages should be built to the following RAC specification detailed in Section (b) or an approved Cross Country Vehicle and Four Wheel Drive design which should in any case incorporate many of the provisions detailed therein.
      2. The roll over bar/cage must be designed to withstand compression forces resulting from the weight of the vehicle coming down on the roll bar/cage structure, and to take fore and aft loads resulting from the vehicle skidding along the ground on its roll structure.
      3. Modified classes must have a full roll cage with two rear facing braces and a cross brace situated either within the main rear hoop or as close as possible to it as per drawing 2 below. The minimum in the standard RTV classes is a screen or roof frame which extends past the height of driver and passenger and fitted by the manufacturer, it is recommended to fit a central roll hoop with rear bracing bars and central diagonal for any open topped vehicle competing in standard RTV as drawing 1 below, this is not mandatory only advisable.
    2. Fabrication
      1. The main hoops and rear braces must connect direct to the chassis by either welding or bolting. One continuous length of tubing must be used for the hoop member with smooth continuous bends and no evidence of crimping or wall failure.
      2. All welding must be of the highest quality with full penetration. Wherever possible gas shielded arc welding should be used.
      3. For space frame vehicles it is important that the roll bar structure is attached in such a way as to spread the load over a wide area. The roll bar should be designed as an extension of the frame.
      4. For monocoque chassis, consideration should be given to using a 360 degree hoop completely around the inside of the vehicle, thus substituting for a frame.
      5. Braces should be of the same size tubing as used for the main structure, their fixing should be located as near as possible to the (top of the roll bar, in any case at a minimum of three quarters of the height of the roll bar.
      6. The mounting plates of the roll bar braces to the chassis must be of steel plate of minimum thickness 3mm, welded, riveted or bolted onto the chassis. The total surface area of each plate should be not less than 120sq cm of which at least one third connects with a chassis vertical member. The chassis outrigger to carry the roll bar mounting must be a minimum of 75mm x 50mm x 3mm box section.
      7. The mounting of the main roll bar hoop(s) must be secured with at least three steel bolts and nuts, hexagonal headed bolts of minimum diameter 8 mm, or by at least three high tensile Allen head cap screws and nuts of at least 8 mm diameter. The attachment plate to the roll bar braces must be of the same thickness as the wall of the tube. When the roll bar rests on a box member of the latter, it must be locally reinforced by a structure constituted of either welded bolt heads or welded tubing ends.
      8. Removable connections used in roll bar design should conform to the recommendations within the MSA blue book.
      9. Bolts and nuts used should be of highest quality steel (preferably aircraft standards) and be of sufficient minimum diameter according to the number used. Square head bolts and nuts are prohibited.
    3. Closed Vehicles
      As a general rule, the safety roll over bar structure must be made of two hoops, one behind the front seats and the other following the windscreen pillars (Refer to current MSA yearbook for full details of all drawings). The structure must be constructed in such a way as not to obstruct access to the front seats and not encroach upon the driver/passenger space. It may encroach upon the rear passenger space and pass through the rear upholstery. The main hoops must be placed as near as possible to the roof. It is permissible to mount a longitudinal support at door level providing it forms part of the structure and is of similar tube dimensions. It may be welded in or located with approved couplings, it must not be higher than one third of the door height above the sill and angled at more than 5 degrees with the horizontal.
    4. Open Vehicles
      To the same specifications as Closed Vehicles, except the main hoop must be symmetrical about the longitudinal center line of the car and complying with current MSA drawings.
    5. Other Considerations
      1. An effective roll over bar must be fitted of a height not less than 50mm at its top edge above the helmet of the normally seated driver. It must be wider than the driver’s shoulders at that height. It must be constructed of steel tubing of minimum 44.30mm diameter with a minimum wall thickness of 3.2mm. It should have a hole of 6mm drilled in the underside for checking the tube thickness. It should have the top bar straight or curved, but not tubes meeting in an inverted ‘V’. It must be effectively braced to a structural member.
      2. Closed vehicles the main roll over bar hoop must be placed as near to the roof as possible.
      3. Non-standard vehicles are advised to fit a safety roll over bar to the following minimum requirements: minimum height 710mm from the rear of the uncompressed seat cushion, of minimum flat width 380mm running into radius corners and affording driver and passenger equal protection. It must be mounted to a structural member with front mountings not less than the cockpit width and braced rearward.
    6. Diagonal Struts
      These should be fitted such that the upper forward joint is on the driver’s side of the vehicle to add further support in the area of the driver’s head.
    7. Materials
      (All dimensions represent minimum requirements.) Tube Specification: Cold drawn seamless carbon steel, minimum yield strength 350 N/, 38mm x 12g for vehicles up to 1500kg. An alternative material is BS1387 medium weight blue band, dimensions being 44.30 mm x 3.2mm for vehicles up to 1000kg or 48.OOmm x 3.2mm for vehicles exceeding 1000kg. All diameters are outside diameters. In all groups recognized manufacturers may utilize a roll over bar of free conception as regards material and tube thickness providing it is able to withstand three simultaneously applied loads:l.5 w lateral5.5 w fore and aft 7.5 w vertical w = weight of vehicle plus 75 kg. Roll over bars of this type must be supported by a duly signed and completed Safety Roll Bar Certificate. The roll bar manufacturer must be registered with the MSA Ltd. Titanium is prohibited.
    8. Roof
      Vehicles in Modified classes (Class 1 and 2) should be fitted with a roof panel if the driver chooses not to use a MSA approved helmet. Specification for roof is :- A panel which is sufficiently strong enough to protect the occupants in the event of a rollover, the panel must cover both occupants adequately. An MSA scrutineer has the final decision as to what is sufficient When fitted to the rollcage it should not be riveted into the tubing.
  12. Overalls
    Overalls are not compulsory but advisable. Oil soaked clothing should not be worn whilst competing.
  13. Crash Helmets
    Crash helmets in Modified classes are to be used if a solid roof is not fitted. A helmet is compulsory in timed trials and team recovery competitions. The helmet must conform to the current RAC MSA regulations listed in the ‘blue book’ in section 0 10.3.1. In the event of purchasing a B.S. 6658-85 ‘A’ type helmet this will have a blue B.S. label attached. You are recommended to consider a helmet with a fire resistant lining, the label will read B.S.6658-85 A F/R and is red in colour, these may be enforced upon us in future years. Helmets with a green B.S. label are not acceptable for motor sport use. Please protect your helmet from external damage by using a helmet bag or similar, chips within the outer laminate of the helmet may make it unsafe and unusable.
  14. Seat Belts
    All Safety Belts must be made out of approved materials and anchored securely in the vehicle. No modification may be made to the seat belt or seat buckles, unless it is carried out by the belt manufacturer. The minimum requirement for RTV trials one diagonal shoulder strap and one abdominal strap, with fixing points on the body or chassis of the vehicle on either side and to the rear of the driver’s seat. The seat integral safety belt design of the Range Rover is acceptable for RTV only. Modified classes must wear a harness of 3,4 or 5 point mounting It is compulsory for all occupants to wear seat belts while competing. The only exceptions to this rule are HGV vehicles competing in Heavy Vehicle trials and any vehicle competing in a Family Vehicle Trial that is not legally required to have seat belts fitted.
  15. Fire Extinguishers
    Products permitted for use within AWDC events are listed in section Q of the current MSA Yearbook. All vehicles must have a handheld extinguisher in the driver/passenger compartment, The minimum requirement for this is as follows: AFFF (manufactured to a standard of 34b) minimum Capacity 1.75 litres, Zero 2000 Minimum capacity 2.25 litres, ViR03 Minimum capacity 2kg.
  16. Classes for Trials Vehicles
Class1The Class for specials and ANs (All Terrain Vehicles). Vehicles may be extensively modified, but must still conform with the Technical Regulations. Four wheel steering, slewing brakes and open centred (dumper) tyres are permitted in this class subject to the ASRs for the event.
Class2The amount of modifications allowed in this class are restricted but do include: changing of chassis lengths, change of spring type, change of engine and/or gearbox type. The axle choice is free. After market differential locking mechanisms are not permitted. Four wheel steering is not permitted. Slewing brakes are not permitted although open centred tyres (subject to prevailing ASRs) are. It is recommended an amount of bodywork be retained to give an impression of the make of the vehicle, this should be easily identifiable by the average spectator. All vehicles must conform to the current technical regulations.
Class3RTV Wheelbase less than 85″
Class4RTV Wheelbase over 85″ but under 100″
Class5RTV Wheelbase 100″ and over.
This standard RTV category is for road going vehicles. The modifications are limited to: Engine conversions; power steering fitment; free choice of wheels and tyres. The fitting of safety equipment of any type is permitted. A front screen frame must be in place as should be a midmounted roof frame when competing (this is the absolute minimum). Tyres such as those described in section 9i. (open centred) are not permitted for use on RTV vehicles. A valid Road Fund Licence must be displayed for that vehicle. Auxiliary lamps and low hanging bodywork (such as sills) may be removed. A FULL width front bumper must be in place.
Class6Allows any vehicle which does not comply with the listed class specifications above such as a home built hybrid to compete in trials. It will be run over the same sections as the RTV trial. There are no wheelbase classes as found in RTV. The only restriction is that open class competitors should not be able to use fiddle brakes if fitted and will need to run on a road tyre as tyre rule 9i. applies to this category.
Classes for Trials Vehicles