Good question which I'd like confirmation on too
From my understanding 1 1/8th Tyres will not fit 20 x 1 3/8ths wheels as 20 x 1 3/8ths are (451mm) a little bigger then 1 1/8th Tyres
Correct me if I'm wrong or if someone has managed to squeeze some on some 20 x 1 3/8ths wheels