Originally Posted by
Jipe
Trailers with a single rear wheel like the BOB put about half of the weight on the rear wheel of the bike and put a lot of torsional constraints on the bike rear wheel+bike rear triangle while trailers with center wheels like the Radical Design, if well loaded put only a small part of the weight on the rear wheel and almost no torsional constraints (the hitch is a ball).
The Bike Friday trailer has its wheels not in the center, so a big part of the load is also on the bike rear wheel (but less than with the BOB) and its wheels are 12" much smaller than the one the Radical Design that rides pretty well and is really lightweight.
But its true that traveling with a trailer has some drawbacks.
If you are riding on hilly gravel, keep in mind that a trailer that transfers some of the total load to the trailer wheel(s) has less weight on the tire that is providing propulsion effort. Less weight on that tire and it can lose traction easier on gravel.
I was on a group tour, one of the people in the group had the trike with trailer in the photo below, he was quite concerned about some gravel uphills where he was not sure if he would have good enough traction because only about 35 to 40 percent (my guess) of his total weight was on the driving wheel.
He made it up the hills, but his concern was partly based on prior experience when he did not have enough weight on the driving wheel to prevent traction loss.