Build Regulations

Build Regulations

The intention (or spirit) of the rules is that racing mowers must retain the appearance of a modified ride-on lawnmower and include a hood, and shall incorporate a bulkhead/firewall, rear body panel, and rear guards. The mowers can be lowered and modifications made to the original chassis to allow fitment of brakes, gearboxes, etc. Similarly, ride-on mowers style bodywork must be used but can be modified to fit wheels, exhausts, seat positions, etc. See the chassis and wheels below. These rules are version 2.0 30/10/2023

All changes and workmanship are subject to scrutineering.

Exposed Chains or Drive Belts

All exposed chains, sprockets, or belts must be fitted with guards that will direct as broken chain or belt downwards.


Engine must be mounted within 100mm of the original location.
Strengthening engine mounting plate may be required, as the twisting of chassis during racing has cracked the sump pan of a few engines.


No forced induction, No supercharging, no turbocharging, no Nitrous oxide .


All mowers must have an operating clutch that can be manual, centrifugal, or may have torque converter.


Must use axle mounted brakes, no factory lawnmower transaxle or transmission brakes. No front brakes. Brakes do require a substantial upgrade, must lock the rear wheels up easily and are subject to scrutineering.


All steering linkages must use ball-type or spherical threaded rod ends, rose joints, or heim joints. Kingpins and wheel bearings to be serviceable. All bolts must have locknuts, Nylock nuts or castellated nuts and split pins. Must be fitted with a Steering wheel and no protruding bars. No bike type handle bars allowed .

Front axle

All steering linkages must use ball-type or spherical threaded rod ends, rose joints or heim joints. Kingpins and wheel bearings to be serviceable. All bolts must have lock nuts, Nylock nuts or castellated nuts and split pins. Front axle is allowed to be fully fabricated.It must be in a fixed position, No suspension, no shock absorbers.
Aluminum may not be used as the material for fabricating the axle or cross member. Front axle and steering may be reinforced, substituted or fabricated

Front Wheels

Shaft locks, centre-drilled axle with locking bolts, castellated nuts with cotter pins, and Nylock nuts with L/R threads are all acceptable for securing front wheels. E-rings and C-rings alone, bent nails, hitch pins, over-centre pins, and quick-release pins are not sufficient for wheel retention and are not approved.

Mower Body

All mowers must have a hood,Guards, rear panels, bulkhead  and mower dash console.They may be modified to fit .Dash consoles may have metal steering support structure.The rear of the mower must be covered to hide any additional structure or bracing. The objective is to retain the appearance of a ride-on lawnmower by using ride-on mower-style bodywork.OEM materials to be used in construction, E.G checker plate or similar material not to be used for structural panels like bonnets , guards etc. Checker plate may be used for foot wells and covers .


A mower must use the original mower chassis/floorpan from the front of the seat forward to the rear of the front axle The mower must have a rear panel to hide the rear axle and framework . Fabrication bracing and strengthening can be made to the original chassis. Fabrication to allow the fitment of brakes, gearboxes, stiffening, and the like is allowed. Emphasis should be on hiding fabrication and modifications behind or underbody panels. 
The objective is to retain the appearance of a lawnmower while improving strength and handling.


Front Bumpers: 
Are not compulsory, but where fitted shall have a centre impact zone of 150 – 180mm from the ground and a maximum width of 650mm.
Rear Bumpers:
Compulsory, recommended with a centre impact zone of 150 – 180mm from the ground, minimum width of 900mm and maximum width of 980mm.
Rear bumpers may not be a single straight pipe and must have a rear-wheel protection area with a minimum overall height of 120mm and maximum overall height of 220mm and the centre of the impact zone as per designs on the spec sheet in the bumper section on the home page.

There are lots of different ideas and designs. The loop-style bumpers are becoming the most popular. Some ideas are bumpers should be flat no hooked ends, no square corners or sharp edges and no protrusions or bolts. shall be vertical, large radiused and closed ends (i.e. no open ends) to cause minimal damage in case of accidental contact.


Throttle controls may be relocated, either hand or foot throttle. The throttle must return to idle when released. All mowers must have brake controls fitted to either the steering wheel or foot area and be easily always activated. The throttle must have two return springs fitted to separate locations.


Exhaust design is open, but must terminate away from driver in a rearward and/or downward direction and not protrude outside the chassis limits and present no apparent safety hazard.


The mower must have an onboard starter that allows the driver to start the mower on the track without leaving the drivers seat.

Overall Width

The maximum width of any mower shall be 1.0 metre (39.4”) at the widest point.


Footholds or side rails are compulsory. They must be constructed in a way to be closed in and not allow the drivers foot to be entangled or trapped in the construction at any time. Maximum height of 120mm across the front half of the foot well floor and minimum height of 180mm from the ground on the outside of the mower. This is the impact zone and is designed to stop the legs being trapped or hit by other mowers in an incident.

Blades or Cutters

All mowers shall have the blades and mowing decks removed.


All positively charged terminals must be insulated with a cover or heavy tape, and the battery must be well secured with a solid approved bracket. Not cable ties and not bungee cord.

Cut off switch

All participating mowers shall be fitted with an operational cut-off switch, of an approved type that is connected to the driver by means of a lanyard. Electric fuel pumps must be deactivated with the removal of the cut-off lanyard.


Factory flywheels must remain stock. No modifications including lightening, removal of fins or alternator magnets is permitted.

Alloy Flywheels

Approved alloy flywheels are allowed in the modified classes only. class 1 2 & 3 but are not compulsory until an engine has a modified or performance camshaft.
Alloy fly wheels are recommended on engines that have had internal performance modifications.

Sharp or dangerous protrusions

Mowers, which have sharp or dangerous protrusions, shall be deemed ineligible for participation. Glass headlights must be taped or removed. No axle or wheel mounting bolts may protrude beyond the face of the tyre sidewall, even if they are under 1meter in width. These faults shall be recorded in their logbooks.

Mowers must be neat and clean

Mowers must be neat and clean and in presentable condition. No excessive dirt, oil, grease, rust, or primer. Sponsor graphics must not interfere with the mower’s racing numbers or class letters.

Rear Rims

Rear rims must be the same size on each axle, made of steel or alloy, minimum 8”, maximum 10” diameter. No dual or tandem wheels. No small go-kart style rims as they deter from the appearance of a racing mower.

Front Rims

Front rims must be made of metal. The front wheel rim diameter must be at least two inches less than the rear wheel rim diameter. Go-kart rims are not permitted. The objective is to retain the appearance of a ride-on lawnmower, with larger wheels at the rear and smaller ones at the front.


The driver’s seat must be of reasonable strength.
Mower seats, kart seats, boat seats, and homemade seats are all permitted. Automotive race car-type
seats with a high back are not allowed as they affect the appearance of a mower too much. The maximum height for the uppermost part of the seat back is 650mm above the centreline of the rear axle. 


1. No ATV-style tyres or nobble tyres are allowed.
2. Only turf tyres as used on mowers may be used on the front and back. Must retain a minimum of two inches between the front and rear tyre size to help maintain the appearance of a mower. 
3. Both tubeless or tube-type tyres can be used.
4. Tyres may not be modified in any way. No cutting re-grooving.

Race Numbers

Every mower shall be issued with a race number, you can view available numbers in the race number section on the home page of the NZLMRA web site. Your NZLMRA club will apply for your race number and supply your chassis tag and log book .Race numbers shall be displayed on the side of all mowers, should be a minimum of 100mm in height, shall be a contrasting colour to the mower,  and must be clear and easy to read.


Driveline may be modified from the engine pulley to the rear wheels, must utilize a lawnmower transmission, transaxle or right angle gear box. or (RAGB).
A wider range of ride on mower gearbox’s is also acceptable.
If a gearbox is built using ride on lawn mower gear box parts, axles and gears this is also acceptable RAGBS that are also acceptable are fertilizer spreader boxes, light commercial mower gearboxes and reduction gearboxes.
The gearbox must be belt driven from the engine.

Rear axle

Rear axle should use shaft locks, shaft locking hubs, centre bolts, or thru-bolts to secure the rear wheels, or hubs Maximum diameter 32mm (1 1/4″).
No Chrome Molly or hollow core kart style  axles are permitted.
Must be solid axle.