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Going Postal
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Discussion Starter #1
Its no secret that lighter vehicles do better in the snow, sand, etc. the heavy pigs like me can compensate for this by running bigger tires and airing down. But how to figure out what you really need to do to get a more equal footing?

I wonder if you could just pull a relational shortcut?

Say...(the weights are tire stuff is just guesses)

The Sammy weighs 2,500 pounds and the tire contact area is 20 square inches. So with four tires we have 31.25 pounds on each square inch of surface area.

(2,500 pounds / 20 square inches)/ 4 tires = 31.25 pounds per inch


I guess the idea would be to try to match the square inch weight load.

So, on a 5,500 pound Blazer....

(5,500 pounds)/(31.25 pounds per inch * 4 tires)= 44 square inches per tire.

So then.....

(44/31.25) - 1 = .408 or 41% increase needed in tire area.

So for fun. Lets say that a 31" tire at full pressure gives you the 31.25 inches of tire contact. 31" * 1.41 is about a 44" tire.

Now this does not include air pressure or lug style or a ton of other things like maybe just airing down a 36" tire can get you what you need.

But it might be safe to say that you would need 40% more tire contact to get the same amount of flotation on the snow.

What do you think?



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I think you have too much time on your hands and aren't working on your blazer.....plus, you gave me a headache... :finger: :finger:
 

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Do you want to float or get traction? A drag slick on snow might be fun but it won't get you very far. :mrgreen:
 

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Flotation is the key of coarse and all that math is fun, but here is what I have experienced.

little to no tire spin is necessary to maintain flotation
very little tread depth is needed to maintain flotation and is acceptable for forward momentum (not racing slicks but close)
extremely low gearing is definitely the key

the doubler is your golden ticket and bald 44's would be just fine

run the snow with no valves in the stems and that helps too, honestly
 

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Going Postal
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Discussion Starter #5
I was looking for more of a general thing and not snow specifically. Those suggestions would not really apply in sand or a thick mud (bottomless) for example.



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Ok. Sounds like you are ready for a set of paddles :thumb: and can come racing with us!
 

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Going Postal
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Discussion Starter #7
Quote:
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So for fun. Lets say that a 31" tire at full pressure gives you the 31.25 inches of tire contact. 31" * 1.41 is about a 44" tire.

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I dont like this one. that means a 44" tire with the same width as a 31" tire. So lets try again.

31" tire * 10.5" wide * 1.41 = Tire Size * Tire Width

So you would need a 31" by 15" tire to make up the difference.

Or a 37" by 12.5" tire.

Not as bad.



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im cornfuzed. Can I just have some big tires and I'll let you know how it works out
 

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It doesn't seem like your getting very far with this idea over here Matt. I believe it is worth further investigation. All falls in with making ours lighter and I know we are both headed in the same direction there. I would like to be able to say I can dump 300 lbs. or get a 1" wider tire next time round or my full size will float better than your jeep. :rotfl:
 

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I think we can agree that this will not be dead nuts science, let's first throw out the never ending sea of different tread patterns. When you come right down to it, under every tread pattern there is a carcass. So if the knobs on your boggers sink down to the carcass you are back to a bald tire anyway as far as contact pressure goes. The vertical surfaces of the tread pattern do nothing for weight displacement only the horizontals.
 

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OK did some measuring and keep in mind my truck weighs 3500 lbs. and the front to rear bias is pretty much zero because of the fact that there is alot missing so these numbers are kinda generic.

44x18.5" tire has a foot print of about 102 square inches with 20 lbs. of air.

Reduced only the pressure for the next measurement down to 5psi.

169 square inches.

Over all four tires we have an increase of 268 square inches. Throwing that around in an excel chart and to equal that amount of flotation gains by reducing weight I would have to find someplace to remove another 2112 pounds.

Keeping in mind that my measuring device is kinda crude. I really would be nice to have an actual mud patch to drop it into and then hoist it straight back out for the foot print. Then smooth it off again for the next measurement. I used a large peice of construction paper and let it make a dimpling in it.
 

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hmmmm... you got me interested in this beyond just mouthing at Matt... :deal: :finger:
I may play with mine a bit with the 38's...hoist it up, then drop it onto a 36" square box about 6" deep with mud in it..then hoist it back out...smooth the mud, play with pressure, repeat as necessary....
 

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There ya go. I have a great big aluminum pan I could fill with mud but just wishing the rig was driveable. My results aren't gona mean nothing till then.
 

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I think you have to take into effect weight transfer and distrubution. Also different materials like snow or sand will be able to support different loads given the same contact patch. mud is probably least stable because you can go deeper in it and it might get more water in it. Sand is probably the most consitent. I think to truly measure your contact patch you would need to put your tire in sand. It would be truly interesting to figure it out mathmatically. :rotfl: :rotfl:
 

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Agreed. All these different things will support different amounts of weight but how much flotation do you need? It's nice to make a truck lighter but maybe at some point its not necessary anymore. Using the Samurai as a sort of guideline and figuring what it has for Contact pressure seems as good a place to start as any. If I can make my blazer have similar contact pressure or weight distribution then maybe its not necessary to remove anymore weight. I'm not saying the Samurai's weight distribution is perfect of anything like that. Just that it is lighter and generally has more ability to float than a 1 tonned 44 wearing GM product.
 

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On another note in the future when my 44's have seen their day I will probably be switching to 49" Iroks. They are an advertised 3" wider so again how much would that do to contract pressure and flotation. As most things go there is a point when you start to lose benefits. Is this true in this case as well?
 
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