It is surprising at first glance, but you can seriously damage your aircraft if you sit it on a trailer and then bounce it. Remember the aircraft structure is designed to take the g's that the rotor dishes out (plus a safety factor) but this is a relatively low number, often at 3 to 4 g's or so. The g's on a poorly sprung trailer on a rough road can be more, and you can bend your helo, or its engine mounts, blades and such.
If you have a g meter that you can mount on a board, just sit it on the trailer bed and drive around a bit, and check the max g. It might surprize you, but that trailer bed would look to your aircraft like a Richter 8 earth quake! You may find that your insurer would not pay for such damage.
In a similar way, I have heard of a pair of Hueys that were seriously damaged while tied down in a C5 during a hard landing - the engines had broken away from their mounts, but the C5 was undamaged.