Floating in snow. How many psi?

[nickw]

I remember seeing an article in Can 4x4 mag awhile ago about snow rigs.
A few of the guys from aqualu where in there. (They build sweet trucks!!! 4 wheel independent with hydraulics!)
How many PSI do you need to float on snow (not tire pressure, but ground pressure). I know mattracks says they end up around 1.5 psi

I was wondering for a suzuki. (or a cruiser). But the psi's will be the same.

2000lb suzuki (not including me and gear and passenger)

Here is what I am thinking. 33 x 12.5 tire on a zuk. Aired down to 5 psi. (can I run that without beadlock? on a 15x8 I know narrow rim = poor mans beadlock.) Guessing a contact patch about 13.5 wide and about 18.5 inches long (just guessing here). So thats close to 250 sq inch per tire. Which means about 1000 sq inches of floation, and around 2psi for the truck.

If me a passenger and gear wieghs 500lbs, that would be 2.5psi total.

What do you need to float? Is 1.5psi overkill like the mattracks?
I am thinking for winter exploring. Both roads and cross county like those icelandic rigs (and norway etc..)?
Why do they get all the fun? We are Canadian after all. We get snow too!

Any when I say float I mean float. IE. Doesn't matter is I am driving on 1foot or 10feet.
Any input?

Thanks,
N.

 

[nickw]

Here is one of the aqualu rigs.
I know they run 2-3 psi (must have bead locks).
Their rigs are all aluminum, and I saw one with a big block v8.
No idea what they weigh in the end. But I know they roll on 44's.

One of the guys won tuff truck a few years ago.
Here is a pic.

 

[nickw]

Based on the 4x4off roads iceland site, they seem to recommend 33x10.5 or so.
http://www.4x4offroads.com/off-road-tire.html

That would only work out to 850 sq inches.
Which would be 3psi me a passenger and gear.
3psi is twice as much as the mattracks.
Seems like a lot. Most sleds seem to have around 1psi or so.

A fully loaded diesel 80 is around 6000lbs right?
44 x 18.5 = 2000sq inches of tire. So that works out to around 3psi.
Maybe its okay?

Also for reference, my sorels are around 12.5 inches long and something like 4.5 wide.
Which is about 110 sq inches. I weigh 200lbs and probably 220 with my gear.
Thats 2psi, and I still sink. But thats not rolling wieght, its on/off wieght, and I guess it doubles to 4psi when I lift one foot. And then 4psi comes down once I put my foot down, and lift the next.

Perhaps my forumula for measuring tire contact area is wrong.
Should there be more length once aired down?
And what sort of psi do I need to stay afloat on average.
I know straigh fluffy pow will take more.
More often than not, there is some sort of base.

Anyways, I have no idea here..
Is there a rule of thumb with psi?
I am just trying to figure it out.
Input appriciated.

Cheers,
N.

 

[Granite Grinder]

Instead of P.S.I. I would be looking C.I.D., 350 +++ . When I lived in Kelowna, my 40 with 35x12.5x15's aired down to 5 psi and lot's of wheel speed got me to a lot of places. Of course, the problems started once you stopped, getting going again was difficult, especially when your front end is packed solid with snow (including the rad). I found I broke beads a lot with mud at that psi, but not so much with snow. There's a reason that all those snow trucks run big blocks... wheel speed and torque! Whoo hoo!!
GG

 

[nickw]

So a zuk that is way way lighter (2000-2500 lbs with me a friend and gear) and 33x12.5 should be no problem then. Should be able to start and stop no easy.

I am thinking, I will either do a little zuk truck up, or an FJ45 (if I can grab the ones I am thinking of)

Would be mostly for summer, and some winter exploring (have a set of bigger tires for winter). I am guessing a cruiser would need to roll on 38's or bigger to stay afloat, and then would need to be able to power them. Hmm, sounds costly.
I like the zuk idea Sounds a lot cheaper to build and run, for the same result (minus some size)

As for blowing beads.
So 5psi and I should be good then. As long as I stick to narrower wheels, and bring some WD40 to reseat the bead if need be.

Cheers,
Nick

 

[canucksafari]

The Trolls in iceland are not big HP. They still just run a turbo TD4.2. Their mods are real big tires, a lot of cutting, suspension and gearing work. You see some of them crossing rivers and you would swear with those big tires they would float in the water. I think they are down around 2-5 psi and from what i have read they don't run beadlocks. They just carry lots of lighter fluid.

GU Troll

GQ Troll

Off course their paddle rigs would float nicely too but at much higher speeds.

 

[nickw]

So I went home, and found my room mates copy of Can 4x4.
They said the big snow rigs weigh around 5500lbs and run a 44's (and 2psi in the tires)
So that in the end works out to 2.75 psi (on the ground).
They said they can sink pretty deep in the snow, so the solution was 500hp+, and keep them turning.

So if a zuk is running 2 - 2.5 psi (say 2.25) with gearing, should be fine.
That is consistent to with what the icelandic guys say (even over kill).
That should make one good, in all but the deepest soft dry fluffy powder.
Any sort of heavier snow, or crust, and you should be good.

If I could fit a 35x12.5 or 15.5 in the wheel well (don't need to much flex) I would run it for the winter.
That would but my PSI in the 1.85 - 2.3 range for a 35x12.5
And 1.5 - 1.9psi range for a 35x15.5 (that would keep you a float and anything.

Cheers,
Nick

 

[nickw]

The Trolls in iceland are not big HP. They still just run a turbo TD4.2. Their mods are real big tires, a lot of cutting, suspension and gearing work. You see some of them crossing rivers and you would swear with those big tires they would float in the water. I think they are down around 2-5 psi and from what i have read they don't run beadlocks. They just carry lots of lighter fluid.

GU Troll

Nice patrol by the way.

A poor mans beadlock is a small narrow rim.
So for those 38x15.5, they are probably running a 15x8 or 15x10

So for a 33x12.5 I would not go any bigger than 8 wide, 6.5 or 7 would be better.
Stock is 5.5 and might be a bit small. But if it was just for winter wheeling, if I could get them on the rim, I would run it.

And then lots of lighter fluid.
Never had to re seat that way. But it looks easy.

Cheers,
N.

 

[Glenn-BJ74]

Poor Man's Beadloc

A poor man's bead lock is a tubeless tire with a tube mounted without tire mounting lubricant.