Hello John,I have run my outfit with a350-16 tyre on the front and sidecar wheels (Heidenau seitenwagen)and a125x15 radial on the rear.I find this to be the ideal combination (sorry!) The outfit steers fine without a bias left or right although left turns might be improved by using stronger rear springs. I have never had problems with unusual tyre wear.Hello, when built about 40 years ago had about 14" of sidecar wheel lead this proved to be dangerous as it would not go round right handers in the wet. I found the reason by reading one of PEIs excellent articles. It has about 10" now, about 1" toe in and around 1" or perhaps a little more lean out. The wheel alignment is fine although the rear wheel has a slight dish to give clearance for the 125 15 tyre. John.