I have heard some Aussies have fear letting air out of their tyres when driving in sand......
Sand is not like water so it is not pushed up, but when the whell sinks down in the sand it is true that the rolling resistance is greater for a wider tyre, but on the other hand the big tyre is beeing less compressed using the same low pressure, and the less deformation of the sidewalls gives lower rollling resistance.
Any way, I am not saying that a wide tyre gives you better performance in sand than a narrower one, asuming that you are driving with the same pressure.
The big tyre containing more air allows you to go with a lower pressure without risking to dammage the rim or tyre. This makes driving on changing surface more easy.
At the same time you get a higer ground-clearance witch sometimes can be good.
I think, it is important to be aware off what you want. Off road capabillities is not necessartly the most important if you are just going from A to B - even on 3.rd world roads. Getting stuck a few times is not at catastrophe driving a 2cv- specially not if you are a team of several cars.

On RAID Oz 2008, there were many different opinions on tyre size and tyre pressure. The only thing everyone agreed on was the standard 125/15 Michelin was best on sealed roads but hopeless under RAID conditions - sidewalls too bulgy and very prone to damage.

Proximity to SE Asia meant that Nankangs were the tyre of choice (ie the only ones available in Australia). They were cheap and they were new. Plus they had a good tread pattern (heavily influenced by Michelin). 135/15 were most popular as they are the best compromise between sealed road and off road conditions. The 145/15 were better in sand and muddy conditions, but were not a good sealed road tyre. Very few people venture to 155/15 tyres as they are more compromised than 145/15. Also, the bigger the rubber, the heavier the tyre, the more compromised the suspension gets. Finally, on all the Australian Raids, you may have 5,000kms of Raid plus another 6,000kms of sealed road to get to and from the Raid.

Everyone had different ideas on tyre pressures. Some had pressures of 32psi which may be good on rocky terrain but transfers too much pounding to the suspension. What would you rather replace - a suspension arm or a tyre? Others let their tyres down to 12psi for sand. I generally kept my 135/15 tyres at 20psi front and 22psi rear. I had no trouble in sand or any other conditions. My co-driver (veteran of 5 previous Aussie Raids) didn't like the 2psi difference between front and rear. He felt that it made the tail a bit more twitchy on loose gravel. I reckoned it gave terrific power steering. I also drive by the accelerator and attack corners agressively.

The 2CV is most forgiving, so you make your choice. We were unable to work out which tyre size and tyre combinations gave the best performance with the least damage. In the end the speeed at which you drive, the speed at which you hit really bad ruts and luck will colour your perceptions. Drive sensibly with new rubber with tyre pressures around 20psi (front) and 22-26psi (rear) and you will be quite happy. A 4" wide brick bolster, ground in an arc that matches the wheel rim is very useful to refurbish damaged rims. Also need a lump hammer to apply appropriate persuasion.

Daffy Duck

I f you can start and stop a loaded 2cv with 20 to 22 psi in the tyres i wouldn't really call it soft sand. If you keep up the speed you can pass with a high pressure. With the wide tyres you can go with a normal pressure about 12 psi with out dammaging the tyre.
Under sandy conditions you can go down to 6 psi like the are doing with the big agriculture machines.

The difference between going with normal pressure and 6 psi is bigger than having 4 wheel drive or two wheel drive - when we are talking about driving in soft sand. The load at the engine and the axels are euqually much lower.

I heardly can't wait until we will be discussing/testing this out in the dunes of Sahara.

On the last Raid Australia 2008, I fitted 4 brand new Nankangs 145/15 on my heavily loaded AK 400. Most likely over loaded being part of the TEC team (tail end Charlie) having engine, gear box and almost everything else in the back. Good thing was that I had no passenger in the AK.
Decided to fit 4 tubes from start and run on “normal” tyre pressure until we hit the dirt and the soft sand. Reduced the pressure to 12 psi on all 4 tyres
I had no problems in the sand except 1 puncture due to an overheated tube. Riding the 10 million corrugations was not a problem, same for gravel and rocky roads. Didn’t break a thing, just cruising along at low speed, taking care of the machine. Others broke swing arms, chassis, rims you name it. I’ve learned what not to do simply by observing others and for this Raid I’ll do what I did down under. It works for me.

Whatever size tyres you choose, remember to take a light hand operated tyre pump. Doesn't take much space and pumps up a 2CV tyre very quickly.

It is a bit slower on non-2CV tyres.

Daffy Duck

You are so right, and i don't think you will be finished for the first ½ hour with the tyre at your photo

The Vredestein tyres work well on my 4x4. I have a couple that have got to have done 75,000 plus miles.

For the ice I have a set of the same tyres factory fitted with studs.

All run with tubes