Just saw some great photos of the group Nb and Ncs out at wakefield in event photos.

Haven't driven Nb / Nc back to back but wondered what differences are felt - or whether a particular track characteristic suits one (Nb or Nc) more than the other or whether our scarcity of tyre options negates differences? Just curious to the effect of CAMS ( the race body not the turning bits) allowed changes over the 1965 to 72 period. 6 inch rim allowed but if you use the same tyres??? what does the extra track width do in terms of performance - theory would suggest a slightly higher cornering speed before losing traction - but does it? Has anyone examples of lap times with similar engine spec - ( eg same engine in group nb and the nc )

as said just curious as to what 'improvements' the poor old mini benefited from in going from Group Nb to Group Nc cheers Darryl

Complicated question to answer but here goes. Group NC allows for other niceties like alloy panels Perspex windows, and flares with 6 inch wheels, so technically an NC car should be quicker if its only for a weight advantage. As far as handling goes the 6 inch wheels have a disadvantage. The offset is pushed further out so the KPI (King Pin Inclination) angle doesn't dissect the wheel properly. Ie the angle of an imaginary line drawn from the top ball joint to the bottom ball joint should meet the road at the centre of the wheel, so that the wheel pivots around that point when turning left and right. If you use a wheel with a larger offset ie 6 inch wheels then when you turn left and right the wheel will scrub, (called the scrub radius) instead of pivot around the KPI. The advantage of using a wider wheel is there is less side wall flex and the contact patch deforms less, which is of particular benefit when using a high side wall profile such as that on a 10inch rim. So if you were running say a sports sedan and wanted better handling with wider wheels to allow wider tyres, you would run longer arms upper, lower and steering arms, to push the hub ball joints outwards, then use wheels that had more inward offset to ensure the centreline of the wheel lines up with the KPI line. Recall back in the 80's cars like Dick Johnsons Greens Tuff falcon had deep dish rear wheels, but the front wheels were very flat looking. Brocky did the same etc and this is the reason why.

Hopefully that explains things a little better.

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1970 Cooper S ex-Bathurst & ATCC
1964 Austin Cooper S ex-Group C race car
1967 Morris Cooper S ex-Group B
1962 Mini Speed sports sedan
1968-71 ex-Peter Manton Shell car