Cadet Chassis Testing

WPKA Goldstar Round 2

Brief History

The current Cadet chassis (Rule K3) was conceived by Kiwi Kart in around 1990/1991, initially for the Hamilton Kart Club. The specifications subsequently adopted in 1995 by KartSport New Zealand (then NZKF) for current Rule K3 were those developed by Kiwi Kart. The chassis tube dimensions in the 1995 Manual stated “2.1mm, NZSI tolerance allowed”. In the 2006 Manual the tolerance was printed to read “2.1mm +/- 0.03mm” (see Further Investigations later). This tolerance remained unchanged until the revision to chassis tube dimensions (2.0mm +/- 0.1mm) announced in Rule Changes 2018-6 published on 21-11-18. 

Most existing Cadet chassis have been produced by Kiwi Kart. Kiwi Kart chassis #’s are now well into the high 200’s. Some of the chassis manufactured by Kiwi Kart have been made to order for local kart shops and “branded” and “stamped” according to the kart shops’ respective imported brand (for larger karts). A smaller number (approx. 10) of chassis were manufactured by Herbert Fabrication & Engineering (branded SPH) and a one off was made by K Nairn (branded Maranello). Imported chassis have come from Australia (manufactured by DPE and marketed as Arrow or Vinart brand) and Italy (Mike Wilson (approx. 10) and BRM (10) brands).

Background to the Current Situation

For some time, the Executive has been receiving complaints and inquiries, with increasing intensity and volume, from members regarding alleged illegal Cadet chassis being used in competition. These inquiries especially intensified during the second half of 2018 and the Technical Department was instructed to investigate the matter and look to establishing a non-destructive test method to check chassis tube and axle tube wall thickness. Something that was also going to be required with the pending introduction into NZ of the Mini 950 chassis (which has been built to a 2.0mm +/- 0.1mm tube specification internationally for many years).

International independent testing organisation SGS was contracted to develop a test method and this method was verified with unofficial testing done at Top Half Round 3 held at KartSport Whangarei on 30 September 2018. This testing was done on Cadet chassis plus on Senior/Junior chassis to provide a comparison of variation. It was interesting to note the very consistent tube thicknesses recorded on the Junior and Senior chassis tested. See Whangarei TH R3 Junior/Senior results HERE.

However, the Cadet chassis tested exhibited a much wider variation, even within the same length of tube. The Competitions Manager then shared and discussed this test data with members of the KartSport Technical Committee. 

All relevant information was tabled at an “In Committee“ session at the Executive Meeting held on 3 November 2018.

After the Executive meeting the Competitions Manager phoned Kiwi Kart and discussed the test results from Whangarei TH R3. During this discussion Kiwi Kart advised that they had been (partially) boring 2.1mm tube down to 2.00mm in order to help level performance with older Kiwi Kart chassis made from other tube. A revised tolerance of 2.0mm +/- 0.1mm was discussed with Kiwi Kart as being more appropriate. 

KartSport New Zealand then followed up with a letter to Kiwi Kart dated 5 December 2018 requesting “a full record of respective chassis numbers for chassis built with either thinner than spec or thicker than spec tube(s)” and noting the “revised tolerance of 2.0mm +/- 0.1mm” published on 21-11-18.

Kiwi Kart responded in mid-January 2019 detailing the broad history of tube used for various groups of chassis numbers and noting that “frames from around #197 (circa late 2010) were made with the front half of the side rails bored to achieve a wall thickness of 2.0mm as well as the front axle and cross bar under the front of the seat. This was done to bring the performance of the Cromoly frame on a par with the earlier carbon manganese tube karts when new.”

Confirmation from Kiwi Kart of “partly bored side rails” probably explains the variances recorded in our testing on the same length of tube. Other variances in wall thickness in the same length of tube may possibly be due to the the boring process. This also explains why some rails, eg the rear chassis rail generally measures consistent across its length and is often quite a lot thicker than parts of the side rail, etc.

This letter from Kiwi Kart was the first formal information that KartSport New Zealand had received that side rails were being partly bored and other rails bored. Hence it is now understandable the concerns, rumours, etc that had been sent our way regarding “illegal bored chassis” with “stiffer rear rails”, all with the objective (perceived or otherwise) of modifying and/or enhancing performance, had substance. 

Kiwi Karts reasoning (see above) was that it “was done to bring the performance of the Cromoly frame on a par with the earlier carbon manganese tube karts when new.”

WPKA Goldstar R2, KartSport Hawkes Bay, 3 March 2019

The matter of Cadet chassis testing was again a topic at the 23 February 2019 Executive Meeting, plus further inwards correspondence from competitors/guardians had been received on the topic. The Executive determined that formal testing must be undertaken at a Group E event before the 2019 National Sprint Championships where testing is also planned.

Hawkes Bay Goldstar R2 became the scene for the formal testing. 

The level of failure was way beyond what was anticipated considering the increased tolerances discussed with Kiwi Kart and published in November 2018.

KartSport New Zealand is especially mindful of, and apologises for, the grief this caused for all concerned; young competitors, parents, guardians and supporters plus our Technical Team and the SGS consultant. 

The testing was being conducted in good faith, based on the investigations detailed above, to help maintain a level playing field for our youngest competitors and to respond to the concerns vigorously expressed to us by competitors/guardians regarding alleged illegal chassis.

KartSport New Zealand is confident the test results obtained by SGS stand up to professional scrutiny.

CLICK HERE for the SGS Goldstar R2 Test Report

CLICK HERE for the SGS Consultant’s qualifications

CLICK HERE for a Calibration Certificate for the Test Wedge used.

CLICK HERE for the Ultrasonic equipment manufacturers commentary regarding accuracy of measurement. A mode 3 – transducer with a delay line was used.

CLICK HERE for a full set of Hawkes Bay Goldstar R2 test results (kart numbers have been removed). Note the results of an Arrow cadet chassis also tested at Hawkes Bay.

Further Investigations

The tolerance of 2.1 +/- 0.03 was recognised as being unrealistic when the investigations on this matter started in earnest during the second half of 2018, hence the discussion with Kiwi Kart to change the tolerance to 2.0mm +/- 0.1mm.

However, since Hawkes Bay Goldstar R2 we have obtained a copy of NZS/BS 3601 1987 which specifies standards for tube tolerances (ref the original 1995 Cadet tube tolerances) plus researched Executive Minutes from 2005 to ascertain when the rule change to the Cadet chassis dimensions, as published in the 2006 Manual, was made.

The following is a copy from the May 2005 Executive Minutes:

Tech Changes
SW (National Tech Officer, Steve Walker) submitted the following Proposed Rule changes from the Technical Committee. Following discussion it was resolved:
Walker/Playle replace Rule F.12.3 Cadet Chassis with the following:

12.3 CHASSIS: As per diagram below. Diagram silhouette obligatory.
Frame tubing: Round 1 1/8 inches (28.6mm) outside diameter unpainted. Wall thickness 0.083 inch (2.1 +/- 0.3mm).
Implementation: Immediate (Clarification)

It is now obvious that when the 2006 Manual was printed in December 2005 the decimal point was mistakenly moved. This mistake has been repeated, and apparantly gone unnoticed by all parties, in the Cadet chassis rule in every Manual issue up until 21 November 2018.

Where To From Here?

Tube Tolerance: Based on the discovery of the 2006 Manual printing error noted above, the tolerance for the Cadet 900 Rule K3.3 is corrected to 2.10mm +/- 0.32mm NO GO with immediate effect. 

WPKA Goldstar R2 Cadet Results: These results will now be subject to a prompt KartSport Inquiry and as such now remain unconfirmed. The Inquiry will obviously take into account the data above. CLICK HERE for the Inquiry Report.

Future of Cadet 900 Chassis: Currently this chassis remains eligible for all events indefinitely. However, in light of the wide(r) tube thickness tolerance for the Cadet 900, the Executive will now be reviewing the future eligibility of the Cadet 900 chassis at Championship and Group E events after 1-1-20.

Introduction Date of Mini 950 Chassis to Cadet ROK class: The Executive will be reviewing the possible earlier (currently 1-11-19) introduction of the Mini 950 chassis for Cadet ROK Club Day competition. 


Once again KartSport New Zealand wishes to apologise to all affected by this matter. As noted above the testing was being conducted in good faith to help maintain a level playing field for our youngest competitors and to respond to the concerns vigorously expressed to us by competitors/guardians regarding alleged illegal chassis. The decision to actually increase the tolerance further will not please everyone.



KartSport New Zealand