Originally Posted by VegasTriker

I presume you are asking about a trike since that is what you have been posting about in the past. I doubt there is any undue stress on the frame for a trike built with a 559 or 700C rear wheel as I haven't seen any posts regarding frame failure at that location. The failures that I have read about usually involve the brazing at the cruciform on a tadpole trike. My CT700 does have noticeable flex in the rear wheel if you lift it off the ground and move the wheel side-to-side by hand. I've never noticed any effect from flex while riding. If you try the same procedure with a good 20" trike wheel like the one on my GS GTO, there is no discernible flex. Utah Trikes sells adapters for some models so you can change the rear wheel. Without and adapter you probably are going to run into interference with the frame. How their adapter affects the flex is probably a question they can answer.

The biggest change is probably in the gear range. The larger the rear wheel, the higher the gear range on both ends.