When it comes to the rear tire size on a trike everyone talks about rolling resistance and smoother ride with a larger tire. My first concern has always been how low the rear derailleur cage is to the ground when in the granny gear or there about when using a 20" tire. This is fine on pavement but don't let your rear tire get buried in soft dirt if you venture off the road. My son did this once some years ago and I spend the afternoon cleaning the grit out of the chain and the derailleur.
|The cage is 1 inch off the ground and close to the tire when in granny gear mode on my wife's Catrike Trail.|
|On my 700 the cage is 5 inches off the ground.|