Thanks Ted for confirming the base and wheels, I hadn't measured the wheel diameters but the last SS Big Bob I replaced 2 wheels with the Pope wheels and held them beside the old broken wheels and they were the same height so someone else must have fitted Pope wheels to my SS before.
As long as you replace all 4 wheels with the Pope wheels there won't be a problem on the SS as the original wheels are 190 mm and the Pope wheels are 180 mm so height will only change 5 mm.
