Why do we air down?

[Antiferret]

Well....

Airing down is not the best in every situation.

It only really benefits wider tyres.

in certain situations (I do stress.. certain situations), a thinner tyre at higher pressure will "dig down" to more firm substrate.

pizza cutters are available for a reason.

Floatation isn't everything (I have a set of wideies and narrow for this purpose).

[SeaComms]

Originally Posted by Wooders

The "formula" isn't out the window - as I said it's not for exactly "measuring" the required pressure.
But just helps explain why you need to increase/ decrease pressures as you vary one of those elements.
I agree that construction variances are also just one of the other variances, however the same basic principles apply.
Problem with a lot of tyre shops is the apprentise looks at the sidewall and sees "max loading 44psi at 950kg" and thinks ok the tyre needs 44 psi, however that's only if the vehicle is currently weighing 3800kg....

Sorry Wooders, I didn't mean the formula was useless, just meant that with different sidewall stiffnesses to use it as the starting point to find the right pressure.

[Wooders]

NP there SC.

Originally Posted by Antiferret

Well....

Airing down is not the best in every situation.

It only really benefits wider tyres.

in certain situations (I do stress.. certain situations), a thinner tyre at higher pressure will "dig down" to more firm substrate.

pizza cutters are available for a reason.

Floatation isn't everything (I have a set of wideies and narrow for this purpose).

I'd partially disagree.
When you air down its not bagging out the sides that the key element, but lengthening the footprint thats the real gain. And in this respect tall skinny tyres actually benefit a lot from airing down.
In some instances yes you might want to cut though the mud to a firmer base, but often that firmer base doesn't exist.
But also sometimes you need max diff clearance which airing down robs.
So like always its a case by case by terrain by terrain thing to determine. But my personal observation is most people do not air down as far as they could or should.


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[Wazza D]

Originally Posted by Wooders

NP there SC.
I'd partially disagree.
When you air down its not bagging out the sides that the key element, but lengthening the footprint thats the real gain. And in this respect tall skinny tyres actually benefit a lot from airing down.
In some instances yes you might want to cut though the mud to a firmer base, but often that firmer base doesn't exist.
But also sometimes you need max diff clearance which airing down robs.
So like always its a case by case by terrain by terrain thing to determine. But my personal observation is most people do not air down as far as they could or should.


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I agree fully with Wooders partial disagreement.
All these modern tyres and wheels were not even available as an option or accessory when I started my off roading experiences.
In the sixties and seventies it was pretty much pizza cutters and that was it. Truck road tyres, mud tread or bar tread.
There was very little information available regarding off roading procedures for the domestic market but we still needed to air down.
This was another problem back then, airing up. I used to carry a petrol powered compressor on the back. Not much of these fancy accessories you get now. Recovery kit was pretty much a chain and a shovel, Pto winch for the privileged.
Even in situations where I have had to cut through the mud, I have not left my tyres at full pressure.
In commercial situations such as mining it is different as it is more about doing the job rather than how far you can get through a quagmire.

[Wooders]

And back then the chain was for the tyres

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[yetiboy01]

I've found that when wheeling with my 35's if I don't drop the tyres pressures down to 10psi I'm wasting my time, the tyres just don't get traction whether in rocks or greasy clay, even at 12psi traction is compromised, on my 37's they go down to 8psi to make them work

Another great benefit of airing down is the ride comfort, the lower the pressure the smoother the ride

[Wazza D]

Originally Posted by Wooders

And back then the chain was for the tyres

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Ha ha. Yes, I have never used tyre chains outside of snow, but my dad did.
But you are very close. I used to carry a veeeeeery looooong bog chain with dogs on each end.
Not being privileged enough to own a winch, if I got hopelessly stuck I could let either the front or rear tyres down low run the chain up around an appropriate anchor and each end back around the tyre diameters. Then go. (Carefully)
You couldn't move very far and the chain feed was a problem but it beat camping out waiting for assistance.
Spools were also available to bolt to your hubs but I have never actually used these either.
The only thing I remember bolting to my hubs was the dreaded duck plucker. Anyone remember them?
Also note Yetiboys post which begins "I've found.........".
This is sort of what I meant in my first post.#12.