Funny, I had a trail for three or four years, and the last year I had it I put a Utah Trikes 26" adapter and new wheel and tire in place, along with some idlers to get rid of those awful chain tubes. I didn't have any trouble with traction at all. The trike was maybe 2 mph faster, average, on a ride, with the big wheel on, but the traction and stuff seemed the same to me. Of course, I was about 260+ lbs at the time, and that puts a lot of load on the tires. You could load your trunk bag with bricks and see if this helps the problem? Traction is always tied to weight as well as torque....
Tractor Tom in Okeechobee, FL