Simpson

Dropping tyre pressures will improve the situation no matter what the wheelbase/rampover relationship is. It sounds counterintuitive but it works because overinflated tyres bite rather than float so you lose any sidewall height advantage before you start by not airing down. Years of towing road based boat trailers with zero clearance up beaches has proven this - tyres down no matter what, and if you get stuck you let them down more - rampover is a luxury which is further down the list unfortunately.

Hi Keith

First of all without being negative, but your comments:-

"Dropping tyre pressures to 20 psi or lower for the sand will reduce ground clearance and make matters worse."

This is the most misleading information that you can give to any vehicle in soft sand. It is drivers that do not drop tyre pressures that are true vandals of the desert and cut the hell out of the tracks and make it harder for the following vehicles.

Just wondering when you drove the Simpson Tracks, what tyre pressures were you running and at what speeds were you travelling. My advise for any new drive to the Simpson is to start at 14psi and you will be able to crawl your way slowly over the dunes and not cut the track up, and clearance is never an issue.

Cheers


Stephen

Stephen,

I think you have misinterpreted what I said. Dropping tyre pressures for sandy conditions is vital, but it does also reduce ground clearance. This is an objective fact. To suggest high pressures to maintain ground clearance is madness.

We started from Mt Dare with 13-16 cold and 13 on the trailer, which went to 16-19 hot and had no problems. I monitored tyre temps with a digital meter whenever we stopped - more out of curiosity than anything else - and they stayed at about 55 degrees.

We went nice and slow and saw no need to rush dunes at any time. The only runup was to get the trailer happily up the Chicken Track at Big Red, with all diffs locked. Did 26 l/100 for the crossing with 3.4 tonnes vehicle and 1200kg trailer. We did not lose traction and did not damage the track, which I mentioned was in good nick earlier in the season.

A lot of people suggest tyre pressures without mention of whether they are hot or cold pressures. Dave at Mount Dare once told me that a lot of people pull up for the night after failing to crest a dune and then find the same dune easy going in the morning, after the tyres had cooled down.

I do wonder whether a 121 inch wheelbase and low ground clearance might be an issue when the dunes switch direction at the crest. Mandatory reduction of tyre pressures for sand will reduce ground clearance.

I think what Stephen is saying is that reducing tyre pressure on a firm surface will certainly reduce ground clearance, but reducing pressure on sand will keep you on top longer. Any increase in clearance by higher pressures on sand is eaten by the tyres sinking further into the sand.

Good point

Hi Keith

No worries and yes I did misinterpret your pressures. You did the correct thing with pressures, but unfortunately not all people do the right thing.

On one of our solo Simpson trips, we could hear a convoy of Tag a long vehicles in front of us having all sorts of trouble getting over the dunes as we were heading west after Big Red. Some of the group were having more than 4 attempts to get over the dunes, on what I could only says as easy dunes to cross. The track was a real mess to so the least and it turned out that there were 9 vehicles in the group.

We held our comments to ourselves thinking that they must be new to sand driving and not knowing their ability, until we heard the guy in charge of the group ask a few of them what tyre pressures they were at........45psi was the reply over the radio, then the leader said try dropping them by 10psi to 35 psi.

I will not tell you what I said to Fiona about these Cowboys and the so call leader. I jumped onto the radio and made contact with one guy that was last and having all sorts of trouble, asked him to stop and I will be there shortly.

We caught up with him in around 15 minutes and he was in all sorts of a pickle, thinking he was going to be left behind and he thought that there was no way he was going to be able to cross the desert at his current rate. Having a chat one on one, we found out the group was 9 vehicles and they had all paid over $2500 just be be lead across the Simpson. When I asked why was he running far too high pressures, the reply was that was what the leader had told them to run, with horror stories of running lower pressures. To make him feel better, I told him to trust must and take no notice of the leader. We dropped his pressures to 18psi hot, knowing they would be around the correct pressure when cold. I told him not to use speed, but just take his time. Then for the dune that had halted him, he went up with easy. He sat at the top and the smile on his face told a thousand word, and I told him I would follow him until he caught up the to the rest of the group that left him alone in the desert.

The rest of the group were having lunch at the Eyre Creek Crossing, where he again made contact with his group. I wished him all the best, and asked him to tell the others in the group to drop their tyres down to the same as I had put his.

That was the last we saw or heard of the group until a few days later at Dalhousie. I greeted the chat that was having all the trouble and asked how did the rest of the group go? He said that only 2 other vehicles dropped their pressures down and they were the only three vehicles that had no more trouble getting over the dunes. He did say that when he asked the leader about the high tyre pressures that they were running, the so called leader called me a smart arse and a few other choice words and who was I to question his experience.

You can now see why I have a dislike for drivers with high tyre pressures in the desert and people who rip people off in the so called Tag a Long groups and do not do the right thing in helping them drive responsibly in the deserts.



Cheers



Stephen

Couldn't agree more. There isn't an argument about what is right, yet some still don't get it.

Someone should invent a hat with brains and hand them out for free.

Good advice on tyre pressures Stephen, THE most important thing in taking pressure off your vehicle / making best progress, after actually using 4WD !! (Some seem to take pride in saying "I did it all in 2WD !!)

But I'd definitely advise do it progressively if travelling west to east (supposedly easier direction) as the dunes in the west are quite significantly smaller, and as you travel east they get larger right through to QAA, which I'm sure most would agree has most of the larger dunes.

It will depend on tyres too, brand, size, type, sidewall stiffness, as to what best pressures are.
The best tyres for this travel have high side walls, stiff AT LT construction, light tread pattern, and don't bag sideways too much, but more lengthwise for longer footprint.

This is all based on the desert generally being dry, sand soft . . .

I'd say with full load in the west region, you could easily start at 22 / 24 or so at Dalhousie, get out to Purni go 18, hit Rig / WAA then after those couple of easy days then go maybe 16 minimum, if needed considering the weight of this beast he's driving.

As he heads more east, and gets to the larger dunes, then the vehicle weight with less fuel, water, beer, food, etc, will allow lower pressures to tackle these dunes and of course get over Big Red.

If he's going east to west, he will have full loads, biggest dunes, most dug up tracks, afternoon sand will be difficult on those steeper sides, especially if dry.
Tyre pressures slightly higher will give the similar footprint as a few psi higher under full load.

I'd much prefer (if in the OPs case) going west to east so it sort of balances load weights / terrain difficulty / tyre pressures very nicely.

Hi Les

Travelling from the west is easier, a sit is a gentle approach to the dunes.

On the other hand we like the extra fun and prefer travelling from the east. The only problem with this is there is no Birdsville at the other end.

As all experienced travellers know, tyre pressures are the key issue for an enjoyable drive across the Simpson.



Cheers



Stephen

Yes, I'm the same now after going both ways a few times either way has it's pros and cons.

I feel the longer west dune faces, while better for lower slope angle, do get rutted very badly as it's the more popular direction, and many don't give up soon enough and have another go, they sit there bogging in.
The east dune faces though generally sharper, you can usually go up them with a little more momentum no worries.
That sort of balances out difficulty.

You just need to be careful taking on Big Red and the bigger eastern dunes too much with full fuel / water / food etc loads.

The best thing about finishing in the west ? A Dalhousie dip :)
The other way, the pub, and June I had a washdown at the town car wash too !!! Very nice :D :D

I'm now concentrating more on north Simpson trips, regular SA crossings seem to get just too easy once you get a little used to the place . . . even Madigan line seems cushy :D !!
I can see me going through again some trips in the future, it's just a peaceful place to take 4 days or so to camp out there . . . maybe some zig zag of the N-S tracks as well, or maybe accessing north Simpson via other tracks into the NT, though need a DPP then for only a little access use.

Happy travels.