The Isetta 3 wheel car originally had 4.80 x 10 cross ply fitted at the front and  a 5.20 x10 cross ply tyres fitted at the rear however these are difficult to obtain now. It is much easier to carry a 4.80 x 10 as a spare because it will fit in the wheel well where as the 5.20 is difficult.You cannot install the 5.20 at the rear of a 3 wheel car without letting the air out as it will not pass the wheel studs!! Some owners are now using 145 x 10 radial tyres with great success however the same problem occurs in the wheel well and the at the rear on 3 wheel cars. If you use Falken radial tyres you may not have to fit wheel spacers part No 1180 to the front wheels on both the 3 and 4 wheel cars. No additional spacers are required on the rear of 4 wheeled cars. Finally as suggestion you may get better results on search engines if you use 4.80 - 10 instead of 4.80  x 10