That 15 mph max speed is just to limit the manufacturer's liability. These trailers tow fine at speeds higher than that. I've had my Burley Flatbed up into the high 30's-almost 40. The thing to remember with trailers is if you have to stop quickly you have the load on the trailer pushing you from behind. Things can get a little exciting if you want to stop quickly with rim brakes in the rain while towing a trailer.