Originally Posted by
kevbo
There is no reason a 4 wheel trailer must be unstable. As has been mentioned ( in British English) multi- trailer semi trucks are done at freeway speeds.
There are some practical considerations that hurt stability:
-The bed often has to be quite high to clear the steering motion of the front wheels. Horse drawn wagons often have smaller front wheels than rear so as to lower the weight.
-Tho tongue on simple solid axle steering needs to be fairly long, or the steering ratio becomes too high. A kingpin arraignment can use the lever ratios to slow the steering
One big problem not mentioned is braking. A two wheeled trailer adds weight to the rear wheel of the tug, increasing traction. A four wheel Trailer has zero tongue weight. Without brakes on the trailer, it will be easy to skid the rear wheel, which is likely to jack-knife the combo. Even if the rear brake is not used, enough weight shift can happiness to cause th rear wheel to become light enough to lose traction.
Good point there, but I feel someone would have to be going fairly fast, not to mention emergency braking, for that particular scenario to happen. The drag from a wagon, even unloaded, would make a high speed pace over flat a little difficult (but there's always steep descents).
Between a wagon's drag and a cargo trailer's wind resistance, I think I prefer the consistent slow down, rather than to be pedaling happily at 12 mph and then have a strong headwind slam into me, forcing me to work harder to maintain speed. Often I succumb and gear down. I just don't suffer that with a wagon, though I'm not going as fast either.
What would be better than both would be a large flatbed. Very little drag or wind resistance, and one could always add rails and it would pretty much be a wagon on two wheels. Of course, that may require some customization, which is personally far from my ability.
Besides a big flatbed, a wagon would be my next choice. Other bike trailers (to me anyway) sometimes feel like riding with an open parachute. Anything smaller than that just don't offer the cargo space I like to have.
That wagon I showed does have a suspension system.