I have found this document written by Peter Vahry in April 2003 and it is quite clear where the idea came from.
TRP REPORT - April 2003
to create a manual to provide recommendations and guidance about modifying or building 4WD vehicles
The original reason for the formation of what we now call the 4WD Technical Review Panel (TRP) was to create a manual to provide recommendations and guidance about modifying or building 4WD vehicles. This was to parallel equivalent reference manuals of other vehicle enthusiast groups such as Hot Rods, sports cars, trikes etc. As the TRP worked on this project it became obvious that so many issues were common. It was decided to create one reference manual with the working title of "The NZ Hobbycar Manual", in conjunction with the other Low Volume Vehicle Technical Association (LVVTA) groups and where necessary recognise specific applications.
It's been a long process of over 2 years so far but it is hoped this year will see a first complete draft emerge. Delaying the process has been the development of low volume vehicle "standards" as required by the Land Transport Safety Authority (LTSA). A low volume vehicle is one that has been modified from original specification in certain component areas. LTSA have developed a guide for WoF inspectors, of "limits" for modifications to vehicles.
(
http://www.ltsa.govt.nz/publications/vi ... tents.html) If the WoF inspector is not happy they may require the vehicle to be inspected by a certifier and have a special plate attached, listing any approved modifications.
The manual needs to address the LVV Standards requirements but those standards are still being developed in several categories. The TRP is contributing to the writing of the standards.
A "standard" category just submitted to LTSA for final approval is "wheels and tyres". LVVTA standards provide the guidance for the low volume vehicle certifiers when they inspect modified vehicles or one-off vehicle construction. Within that wheels and tyres standard the TRP managed to have included a bead-lock wheel construction, after months of consultation with local manufacturers and reviewing overseas material. Wheels built to the standard still need to be certified on the vehicle they were intended for but the process is now clear. An eventual ideal is to establish a "type approval" system for a vehicle component made to a standard by a reputable manufacturer.
In regard to wheel and tyre size changes we understand that LTSA have recently set a maximum variation of 5% in rolling circumference from "factory standard" (whatever that is on some makes and models!) before the vehicle must be certified. This may mean having evidence available of the compliance of your non-standard diameter wheels and tyres when you visit the WoF man in future. It may pay to remove the manufacturer's tyre specification sticker off your vehicle to start with!
There is no question that big wheels and tyres do change the handling of a vehicle and the effects on braking can be dangerous. The NZFWDA advocated a maximum of 15% variation. LTSA have argued on speedometer accuracy effects too. I don't think they're trying to save us from speeding fines but are looking at diesel road tax.
For many years, MotorSport NZ has been the only organisation allowed to issue "Authority Cards" recognising some modifications to vehicles used for competition, which would otherwise prevent their use on public roads. Components such as certain seat belt types, roll cages etc. are acknowledged by an authority card that is recognised by WoF inspectors. The LTSA have now identified that there are other motoring contests outside of Motorsport NZ and are allowing other administering bodies to also issue authority cards. The process is complex and must be well managed. NZ Hot Rod Association has indicated they might be able to work with the NZFWDA to provide a scheme if there is a requirement by competitive four wheelers. I'd be interested to hear from members on that.
There is still a lot of work for the 4WD TRP this year, as several standards are still to be completed, or even started. One area of interest is a bull bar policy that is still on the shelf. A "noise and emissions" rule and standard has been given urgency by LTSA with emphasis on the noise part. Creating a workable standard and test parameters will be a challenge! A "seat and seat anchorage standard" final draft is soon to be circulated to contributors for comment. This may affect some four wheelers who swap seats from other vehicles or install aftermarket units.
So, you can see many things influence the production of the manual, but the aim is to at least reflect the intentions of the standards in good engineering practice. In the meantime the team will keep monitoring regulations in association with the LVVTA.
The role of the NZFWDA delegate to the LVVTA is to represent our organisation's interests through attendance at about three meetings a year, advocate for 4WD and monitor the draft standards and other documents circulated for comment. LVVTA are presently restructuring their staff positions pending the retirement of Glenn Johnston who has done a great job as Executive Officer in clarifying the role of LVVTA within the LTSA and setting up processes to administer LVVTA. The present Management Committee of LVVTA comprises 2 elected members plus the President, currently President Neil Fraser, Steve Keys (NZHRA) and Ian Snellgrove (MotorSport NZ).
Peter Vahry
