Group ND Proposal
Wheels maybe increased in diameter by no more than 2 inches
Wheel design and construction must be compatible with the PERIOD save that magnesium construction and/or centre lock single nut arrangements are prohibited.
Maximum permitted rim width:
- Class A and B Maximum 9 inches (typically 245, 255 tyre)
- Class C, D and E Maximum 8 inches (typically 225, 235 tyre)
- Class F and G Maximum 6.5 inches (typically 205, 215 tyre)
Wheel nave plates or covers must be removed
Any wheel to hub spacers used must be securely fitted, not slip on
Justification and Rationale
Simplification in line with ever increasing size of wheels found on production cars in the PERIOD
The prohibition on magnesium and centre lock wheel is to cap costs and increase safety in an amateur sport.
Note: Allowing a maximum of 2 Inch increase will permit drivers to upsize to a rim/tyre combination where race tyres are available, 14" and 16" rims are common on ND era cars and race tyres are already obsolete for most common brands.
there was a cost consideration in the suggested sizes. also, capping the width in the biggest engined /heaviest cars was an attempt to limit their cornering speeds. replicating the Dick Johnson 19 x 12" rear wheels might be problematic for finding suitable tyres. We know diameters smaller than 17" are becoming harder and harder to get in semi slicks. Im doing a survey of what sizes are actually "buyable" in australia and will reveal the findings soon .
Apart from the V8's, my memory was the bulk of the field used either 13 or 15' diameter and up to about 10" wide. In a lot of cases, especially with amateurs, tyre availability played a big role in wheel sizes used.