Are huge tyres worth it?

... which reminds me how much I HATE Qld's ridiculous restrictions on overall tyre diameter being no more than +15mm rolling diameter from standard factory tyre !

Yesterday I heard the most plausible explanation yet of 'what happened' from a work colleague who has just moved from the top end of the Northern Territory and had to use a 4wd to get to work each day for half the year during the wet season.

The mud was heavy, but also quite wet and thin on the top. Wide tyres with a large surface area tend to sit on top and just spin. Thin tyres with less surface area place more pressure on the mud which allows them to dig down through it to the harder earth below.

If the mud was too deep the Landy could have gotten stuck as well. If it was a sandy beach the Nissan would have been able to walk over what the Landy would have sunk in, but the Landy could have it's tyres let down to achieve the same surface area (due to the high walls of the tyres).

In any situation thin high walled tyres should be used at maximum pressure and only let down when you are already bogged.

With thin high walled tyres it is possible to have your cake and eat it, with wide tyres they always have a large surface area and in some terrain are a disadvantage. He said this is why the military chooses them. When I said to him that someone on this forum had commented that the military chooses them because they are cheaper he laughed and said "do you really think that the Army or any military force in the world would spend millions on modifying vehicles to cover all terrains then skimp on tyres??, people just put on fat tyres because they look better."

Up until yesterday I had been seriously considering trying out some big widey's, but after hearing this guys confident explanation who claims to have 4wd'n through some of the remotest sections of Australia on thin tyres, I'm going to stick with the thinny's. After all, I can just let them down if I get bogged.

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Originally Posted by blitz

one of the hardest things to quantify is the driver. Iv'e seen good drivers do things in fairly standard rigs that a novice couldn't do no matter how well set up the vehicle.

In my experience big tyres are great in sand, in mud really aggresive tread is perhaps the most important factor, with rocks it's ground clearance; horses for courses.

but I still think the most important factor is the driver who can answer three simple questions

1. is the vehicle capable of doing it
2. am I capable of doing it
3. do I really need to do it

if the person can honestly answer yes to all three then they have a fair chance of getting through but even then sometimes things go pair shaped.

Blythe

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we do go many spots where were do not really need to do it, but go there because it is there.

Makes a lot of sense, TJ.

That would mean your absolutely essential equipment would have to include a compressor. Have you thought about what type is best?

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Originally Posted by lane

Makes a lot of sense, TJ.

That would mean your absolutely essential equipment would have to include a compressor. Have you thought about what type is best?

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Yep, my brother made a setup in a LWB Series ten years ago that was simply an airconditioner compressor mounted on it's standard bracket that he had bought from the dump for $2. He had a little oil filter on the inlet and a detachable air hose / hand piece in a box under the bonnet for the outlet ($60 from an auto parts store). I have NEVER seen a tyre pumped up so fast!!! You had to be careful not to over inflate.

Sounds like a low-cost, effective, set-up!

This is another option, of course: [ame="http://www.youtube.com/watch?v=CW_TYS_Gv9k"]YouTube - how to inflate a tyre[/ame]

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Originally Posted by TJWA

The mud was heavy, but also quite wet and thin on the top. Wide tyres with a large surface area tend to sit on top and just spin. Thin tyres with less surface area place more pressure on the mud which allows them to dig down through it to the harder earth below.

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Except you can see where you went through compared to where your mate went through. Your mate didn't "sit on top and spin" he dug down far deeper than your skinny tyres did.

I am not in the military so I do not know why they run the tyres they do, however 7.50x16s are the size that were (and still are) specced by the manufacturer. The military is also probably more concerned with reliability (minimising punctures) rather than a slight increase in traction.

In most (inland) WA terrain, 7.50x16 tyres will probably do just as well as wider tyres, and likely be less prone to staking. IME, however, wider tyres tend to do better on rock and sand.

I disagree with "only let them down when you get stuck" - letting them down beforehand can often mean you cruise through without getting stuck and needing a difficult and time consuming recovery - like on the beach when the tide is coming in.

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Originally Posted by lane

Sounds like a low-cost, effective, set-up!

This is another option, of course:

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Air con compressors like TJWA describes above are great. I put up a 20m fence with mine once (running a nail gun).

The aerosol method you show is just for bead reseating - you still need a compressor for inflation. You need to remove the valve core when researing using that method, otherwise the valve stem will be blown out if you use too much aerosol.

You may be right, I'll take it on board.

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Originally Posted by TJWA

You may be right, I'll take it on board.

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Any time you want to bring the SIII up north, we can do a comparison of your skinny tyres against my old hard 285s - on almost identical vehicles on the same terrain...

However we each get to run whatever tyre pressure we wish.

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Originally Posted by isuzurover

Any time you want to bring the SIII up north, we can do a comparison of your skinny tyres against my old hard 285s - on almost identical vehicles on the same terrain...

However we each get to run whatever tyre pressure we wish.

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Would be good to get a heap of us together in Series vehicles at a place like Big Tree Road or the Powerline Track behind Perth!