I returned from a Simpson trip about 5 weeks ago and yes I towed a trailer which weighs in at about 8-900kg.
My opinion is if you do the right thing and lower your pressures all round your life will be easier, you'll also make life easier for others that follow you.
I haven't done a lot of back-to-back testing to confirm but my experience is lower tyre pressures on the trailer in soft sand does make a noticeable difference. The longer footprint the lower pressures provide lets the trailer float on the sand. My opinion is the increased rolling resistance of a low pressure tyre is offset (significantly) by the increased footprint.
One of the biggest issues I see with trailers is weight of some of them, when loaded. I'd hazard a guess many trailers people are towing out there exceed 1000kg and to be honest I'd hate to be pulling that much weight in soft sand. If you pull a heavy trailer in 2wd or 4WD with highway pressures all you do is use more fuel and increase damage to your vehicle and the track in my experience.
In terms of track damage the biggest problem I see with high(er) pressures is the way the track seems to get scalloped after the tyres dig a hole, grab traction, lose traction, dig a hole, grab traction etc..... This usually results in opposing holes which means you either need to drive flatout to maintain momentum or try to walk up the dune slowly. Most of the dunes I've driven you could walk up at a controlled and comfortable pace. A smaller number of longer, steeper dunes with this type of damage you couldn't take this approach as you would bog in soft sand toward the top of the dun even with low pressures and 4WD.
This would mean you'd need to reverse back and hit the dune with speed and hope for the best, far from a comfortable ride and often hard on the vehicle, occupants and other contents. Backing a trailer in soft sand can be a real bugger too, even if you can back a trailer well you'll often have problems at one time or another.
One to tyre pressures - we had six vehicles on our trip and half were not convinced about low pressures particularly when on the dirt. The first puncture they had and then the first dune they could get up easily also changed their outlook on the value of letting air out of your tyres. The comments in sand were along the line of "*hit, that makes it easier". Even with low pressures you still need to resort to speed to get you up and over a dune, you don't need to do it as often though.
The concerns most people seem to have about low pressures are:
- I'll roll the tyre off the rim
- I'll get a puncture
- There are others, I just can't think of them at the minute
With the lower pressures we were running we had NO tyre problems, as soon as people lifted their pressures (on fast dirt in particular) they blew tyres, I was one of them BTW. The roads the tyres blew on were better than many desert tracks we drove too, for those of you who have driven from Mt Dare to Dalhousie will know bad some desert roads can get.
My top tip is to adjust and check your pressures when hot, not cold. For the desert we were down to 18psi HOT, my trailer was down to 13psi. When I did Big Red I was down to 14 and 9. Another thing you should try is sway bar disconnects, particularly on live axle vehicles. I drive a Jeep so this is a common accessory, when employed it makes the front end much more flexible/compliant which results in a much smoother ride with less side-to-side rocking and rolling.
I hope they don't ban trailers as I'm of the opinion you need to tow a trailer if you want to keep your vehicle legal. I'm mostly concerned about overloading as many 4WDs have vey small payloads, 600kg seems to be the norm. With a trailer you've got a fighting chance of keeping the vehicle weight to realistic and safer number.
If you are going to tow a trailer in the desert, think seriously about what you take with you to keep your weights as low as possible.
As for corrugations, there is research out there if you want to look, the findings are interesting, here is one link I found quickly:
http://perso.ens-lyon.fr/nicolas.taberlet/washboard/