A question that comes up frequently is about the differences between Cooper S rims and reverse rims.
Well, here is the answer!
The Cooper S used a 9 hole ventilated rim.
The standard factory fitment to the 'S' was 3.5" wide.
An optional 4.5" wide rim was offered.
The 'S' brakes had the wheel mounting face set further out than the drum brakes.
Therefore, the wheel had to be more 'inset' than the drum type wheel in order to remain under the bodywork.
'S' rims do not fit drum brake cars without using spacers.
Reverse rims were introduced to allow the use of the 4.5" rim on drum brakes.
These were more 'offset' than the 'S' type to fit on drum brakes.
Reverse rims extend beyond the body when fitted to an 'S'.
Reverse rims were available with 9 hole or standard centres.
997 & 998 Coopers were never fitted with ventilated wheels by the factory.
Below is a diagram showing approximate backface dimensions of the 4.5" wheels.
This is measured from the inside edge of the rim to the mounting face of the wheel.