Yes it seems that with the old wheels being 2.1" rather than true 2" & with their tyres generally coming up a little small, means you can actually run new tyres on old rims.... the 2wd stagger ribs especially seem to fit the old Schumacher wheels really well!
I can remember there being different profiles of Schumacher tyres - Minispikes especially were very 'baloony' - I wonder if it was so that the O/A of the tyres measured from the tip of the spike were about the same dia as say a full spike? - So gearing wouldn't change with a change of tyre? However I do remember there being some super low-profile mini spike tyres - but I have a feeling these were Schumacher copies (Amark perhaps?)
Schumacher still sell old 2" tyres in block & full spike treads - regular rears & wide (4wd style) fronts - the block tyres in modern yellow compound work really well on the high grip astro at my local club - even the modern buggies are using them stretched around 2.2" wheels (which are also wider) - so these are what I'm using;
