Peter and Tim are spot on here.
Morgan wheel widths have increased over the years , and the handling is no longer optimal for the design of the chassis and suspension. You want to be able to drift a Morgan under control, preferably with all four wheels. As the contact patch increases so does the grip, so now it lets go at higher cornering forces (usually speed related) and you need much better car control in order to be able to tame it.
My 1950s +4 race car handled best on 165 x15 tyres (85 section?) and could be easily drifted under full control of the driver. Eventually I progressed to 6 inch Cobra wires and 185/60 x 15 "sticky" Yokohamas , the grip was much higher, but the breakaway speeds meant that catching it required a lot of skill (and probably not a little luck on occasions)
Tim is correct here, you want to be able to provoke breakaway , but you also want to be able to catch it easily with needing a change of underwear each time.
In the 60s, the widths were 4.5 and 5 inches, and the cars handled really well, mainly on bias ply tyres in those days. Once radial plies came along the width started to increase slowly but surely until we now have 6.5 inch and wider tyres to suit. Yes the grip is better , but for this to be optimal a much stiffer chassis is required, and this is outside the operating envelope of most trad Morgans.
I would go to 185 width and 70 profile maximum.
My +8 resides on factory alloys with 205/60 x 15 tyres, it tramlines everywhere, it can be a handful (especially in the wet) and it just feels over-tyred for the chassis. I would fit Avon CR6ZZ in 185/70 x 15 (if the price was more reasonable), but I have been informed that 185 section on 6.5 inch rims is too much of a stretch and not recommended.
