I replaced the 14" Motolita wheel with a 15" model, which I had lying around in the garage, just out of curiosity. Interesting effect: Steering effort is significantly reduced, but getting in and out of the Morgan is not as easy as it was before due to reduced space between the wheel and the seat. And changing direction at roundabouts is somewhat slower because you have a larger wheel to turn. But I like the feeling of the larger wheel, it also reduces the feedback forces, which makes driving on bad roads smoother.
