Airing Down Vs.----------Not

[Chris Green90]

T'other Chris had a little mention over on Ben's Build thread earlier in regards to airing down. I have found that most of my local lot running the Simex (insa) tread pattern tend not to and TBF I can see the logic. The point of a MT is that it "digs" into the soft stuff and pulls the truck forward therefore the higher the psi/lower the surface area the better as opposed to an AT where the idea is to create plenty of friction to pull the motor along whereby low psi and therefore higher surface area is better.

Please Discuss

 

[Shayne]

Speaking from my experience driving diggers , site forklifts and dumper trucks i believe "tricks of the trade" are best left in the tool box until a situation demands they be brought out if you get what i mean . Difflocks and airing down are safeguards . If you drive into a situation with all your tricks already employed and get stuck , you will not get out without assistance . But if you reach the limits of your trucks natural ability and get stuck , engaging the diff or airing down just might give you the edge you need to escape .

On a 4x4 play day with lots of like minded people around to help out it doesn't really matter , but alone in snow or out on a trail .................

 

[Paul_Humphreys]

Speaking from my experience driving diggers , site forklifts and dumper trucks i believe "tricks of the trade" are best left in the tool box until a situation demands they be brought out if you get what i mean . Difflocks and airing down are safeguards . If you drive into a situation with all your tricks already employed and get stuck , you will not get out without assistance . But if you reach the limits of your trucks natural ability and get stuck , engaging the diff or airing down just might give you the edge you need to escape .

Someone else who drives like I do most of the time.

 

[stumog]

I was playing with this concept in moz on the sand. and there was a massive differance there. IF you can keep the momentum going then you used a lot more throttle to move but as soon as you backed off the sand just sucked ypu in and there you stayed until you let the tyres down.
On hard packed i run high pressure to stop pinch flats. snow i let a fair bit of air out.
I went to recover a bus stuck on a school field. just let tyres down and away.
I really think it depends on how much flex the side walls have. bfgs thin side wall so will make a massive difference but something like a xzl 8ply dont think it makes as much difference.
Stu

 

[Olazz]

I have MT Baja claw TTC's and at anything below 20psi the side walls don't deform or collapse. So in Moz & Bots last year, we were drove in thick, axle deep sand at no less than 20 psi. Never got stuck once.

Even spent a day at Atlantis Dunes and ran at 25psi without problems.

So it does work, but I can't see 10psi being of any advantage if you have tyres that don't deform.

 

[Chris]

Just to be clear, I didn't say that airing down doesn't work. It most definitely does. But just airing down as a standard practice makes no sense unless the situation is right. Crossing glaciers in Iceland with monster tyres at 5 psi works. Rock crawling with balloons certainly does. Sand driving on slicks may do, but just airing down in a standard off road situation may not actually be helpful. I found that I lost grip. I lost the 'sharpness' of the tyre. The next day fully aired up, I monstered things like the steps at Lincomb where the day before on softies I couldn't get up. Sure sure there are other variables, but having done this a few times in as I said normal off road stuff, harder tyres seems far better. I think that airing down might be as Shayne said, a countermeasure that you might try. But "Ahh we're here, let's let the air out' isn't necessarily the right approach. This is for my tyres, huge great big things that will actually run with no air in. I had a bit of a wobble and checked my pressures and truthfully, one tyre had zero psi in it and I didn't know. Letting the air out does not make it flatten out like a floatation tyre on a tractor.

 

[Ben]

Great thread and some interesting ideas.

I always airdown when I leave the tarmac. This is mainly as its too bumpy off road on my tyres at 30-35psi, so I air down to 20psi.

As many of you know I then air down the 37"s to as low as 10psi when I get to any really challenging bits.

But I will definitely be trying them at 20psi and not going any lower.

My friend Michaels 37" super sticky Maxxis trepadors definitely benefit from dropping tyre pressures as they mould beautifully around rocks!

But my 37" simex style simply don't!

Without going off the subject too much..................................

I've found my 37" simex style tyres simply dont work as well off road down here as I thought they did in the UK. Maybe theres less mud over here, I dont know.

The Trepadors would be my first choice for off road tyres now having seen how well they work off road and how all the comp guys run them.

I'm going to try Michaels on my cruiser at some point and see how they do.

 

[Shayne]

Maybe theres less mud over here, I dont know. :

Simplest way to describe mud is a mixture of clay and sand . Seems reasonable to suggest there is far more sand than clay in Oz while the opposite is true in the UK . Perhaps something to consider while discussing tyres on an international forum ?

 

[Chris Green90]

I think mud is defined as a mixture of earth and water. Define earth as what you will. Chances are there is less water way down there.

 

[clivehorridge]

Up my way when there's mud, its saturated clay, very sticky and so much so that it's almost impossible to spin it out of BFG MTs.

When it's dry the same stuff is like concrete.

Topsoil around here is sandy. because of that it drains and rarely turns to mud unless the clay layer is close to the surface which stops the soil draining.

Anyway, I never air down as a matter of course, but I have done it to get me out of some difficulties. Never tried it with the BFG MTs but it worked when I was off-roading on the GG AT2s climbing some rock steps in the wet.