Ground pressure poll

[Skid Mark]

So with such a variety of tires, vehicles and terrain. I wanted to get a look accost the board of what kinda of terrain do you wheel and whats the ground pressure of your rig.

With some chalk draw a circle around one tire as close as you can get to the tire move your rig and calculate your square inches and times x4 Do the math with the with the weight of your rig divided by your overall sq inches to find out your ground pressure psi

list vehicle, weight. Size and air pressure of tire Along with preferred terrain

thx

 

[jprcrpr94]

That sounds like a lot of work. I don't want to do that.

 

[Skid Mark]

That sounds like a lot of work. I don't want to do that.

Then just make something up

 

[64FJ40]

You are making this way harder than it needs to be.

Ground pressure PSI averaged over the entire contact patch is going to be virtually identical to the tire inflation psi.

If you want to get technical about it, you could calculate the tread void percentage to get a contact point pressure for the tread blocks.

 

[Binder]

So with such a variety of tires, vehicles and terrain. I wanted to get a look accost the board of what kinda of terrain do you wheel and whats the ground pressure of your rig.

With some chalk draw a circle around one tire as close as you can get to the tire move your rig and calculate your square inches and times x4 Do the math with the with the weight of your rig divided by your overall sq inches to find out your ground pressure psi

list vehicle, weight. Size and air pressure of tire Along with preferred terrain

thx

You're assuming that there are people here who have a rig with tires on it to do all of that.

 

[Eric]

That sounds like a lot of work. I don't want to do that.

Way to much work. And what happens if your truck is parked in mud or on concrete? or in snow right now?

To many variables.

 

[Boonie Buster]

Just so you know you can't just divide by 4. There is weight bias. :eeek:

I just weighed mine the other night, 2240 in front, divide by two, 1120 per front tire, 1600 in the rear, 800 per rear tire. On 32x11.5x15 MT's at street pressure (unknown).

Plus, No Boobies or Pizza.

This thread brings the Fail Boat straight from Failedelphia back to Fail Island in the Failippines.

 

[Skid Mark]

You are making this way harder than it needs to be.

Ground pressure PSI averaged over the entire contact patch is going to be virtually identical to the tire inflation psi.

If you want to get technical about it, you could calculate the tread void percentage to get a contact point pressure for the tread blocks.

Hints the fact I said what kind of terrain soft or hard. I.e Assuming a standerd base number in soft surface's and an increased amount of gppsi when on hard surface's average. The poll is to get an over all idea of the spectrum across the board not a debate.

You're assuming that there are people here who have a rig with tires on it to do all of that.

LMAO

Way to much work. And what happens if your truck is parked in mud or on concrete? or in snow right now?

To many variables.

Read first response in post not a debate rather a perspective of diversity

Just so you know you can't just divide by 4. There is weight bias. :eeek:

I just weighed mine the other night, 2240 in front, divide by two, 1120 per front tire, 1600 in the rear, 800 per rear tire. On 32x11.5x15 MT's at street pressure (unknown).

Plus, No Boobies or Pizza.

This thread brings the Fail Boat straight from Failedelphia back to Fail Island in the Failippines.

Ok rapping fortay first I had whiskey and split-tail If you don't like whiskey and split-tail I'm sorry I get board with just beer and boobs.
I understand the weight bias hell think about if your on a side hill vert and sitting one tire that changes it as well.
I'm just looking for a approximate number to do a rig tire vs terrain perspective and see what works accost the board.
If just a dozen or so people post up a little verity in rigs and tires It might be a useful tool for... tools who are looking to buy tires

By the standerd response I figure everyones just hungover, stoned or just lazy its not rocket since and doesn't have to have the level of perfection some of you build your rigs to




816 inches of contact with my 33/12.5 @12 psi. My jeep prepared to go is about 5500lbs so ON AVERAGE I have a 6.74 gppsi

 

[Eric]

ummm you ever tried to use chaulk in mud? or snow?

I know fully what you are asking, but I dont think you fully understood by question.

I know that on differnt terrain you run differnt pressures. My question was how are you going to measure the contact patch in softer soil over concrete. If your rig is parked in mud or on mud right now. You are going to have a much differnt contact patch then if you move the same rig to concrete a few feet away.

 

[unclestripey]

You are making this way harder than it needs to be.

Ground pressure PSI averaged over the entire contact patch is going to be virtually identical to the tire inflation psi.

If you want to get technical about it, you could calculate the tread void percentage to get a contact point pressure for the tread blocks.

Okay--color me stupid.....Are you saying a light rig(sami) will have the same ground pressure as as say.....a suburban? If they're both at say 10 psi tire pressure? :eeek:

 

[jprcrpr94]

 

[jprcrpr94]

 

[ain'tstuckjustresting]

This thread brings the suck!:BJ:

My 2yo. can spell better than you.:Ironsheik:

 

[64FJ40]

Okay--color me stupid.....Are you saying a light rig(sami) will have the same ground pressure as as say.....a suburban? If they're both at say 10 psi tire pressure? :eeek:

I'm not sure exactly what "ground pressure" means. Not because I don't understand the forces involved, but because it's not a real term. My interpretation of Skid Mark's original post seems to indicate that it's the weight of the vehicle (at each tire) divided by the contact patch area. My assertion is that you could save yourself a lot of drawing, measuring, weighing, and calculating by just using a tire pressure gauge.

Here's why: the pressure inside the tire is (more or less) equal to the pressure outside. It's not exact because the stiffness of the tire carcass and the shape of the tread at the shoulders may affect the uniform deflection of the tire, causing non-uniform pressure within the contact patch. It's not perfect, but it's a lot more accurate than chalk on the ground.


I'll explain a little bit more explicitly what I'm saying using bits from your scenario and some make-believe numbers. We have a Zuk and Burb, both on 33x12.50 BFG MTs at 10 psi. For simplicity's sake, they both have a 50/50 weight bias. Each tire of the Zuk has a downward force of 750 pounds. Each tire of the Burb has a downward force of 1500 pounds.

Using those numbers, the contact patch of the Zuk's tire is 75 square inches; the Burb's is 150 square inches. The contact patch must be twice the size because the force is doubled, but the pressure (which is measured in force/area) remains the same. If you built a device to measure the weight over a 6"x6" area under the contact patch of each rig's tires, it would read the same weight for both rigs (roughly 360 pounds).

To extraploate further, I'm guessing the BFG MT's tread pattern to be about 75% void space, which means the weight distributed over the entire contact patch is actually being carried on about 25% of the "contact patch" area. So the contact pressure of the tread block against the surface is actually more like 40psi.

To further the uncertainty, every tire size and tread pattern has a different void percentage.



That's why this whole thread makes no sense. It would have been much more informative and useful to ask "What tire pressure do you run for different terrains?"

 

[unclestripey]

I'm not sure exactly what "ground pressure" means. Not because I don't understand the forces involved, but because it's not a real term. My interpretation of Skid Mark's original post seems to indicate that it's the weight of the vehicle (at each tire) divided by the contact patch area. My assertion is that you could save yourself a lot of drawing, measuring, weighing, and calculating by just using a tire pressure gauge.

Here's why: the pressure inside the tire is (more or less) equal to the pressure outside. It's not exact because the stiffness of the tire carcass and the shape of the tread at the shoulders may affect the uniform deflection of the tire, causing non-uniform pressure within the contact patch. It's not perfect, but it's a lot more accurate than chalk on the ground.


I'll explain a little bit more explicitly what I'm saying using bits from your scenario and some make-believe numbers. We have a Zuk and Burb, both on 33x12.50 BFG MTs at 10 psi. For simplicity's sake, they both have a 50/50 weight bias. Each tire of the Zuk has a downward force of 750 pounds. Each tire of the Burb has a downward force of 1500 pounds.

Using those numbers, the contact patch of the Zuk's tire is 75 square inches; the Burb's is 150 square inches. The contact patch must be twice the size because the force is doubled, but the pressure (which is measured in force/area) remains the same. If you built a device to measure the weight over a 6"x6" area under the contact patch of each rig's tires, it would read the same weight for both rigs (roughly 360 pounds).

To extraploate further, I'm guessing the BFG MT's tread pattern to be about 75% void space, which means the weight distributed over the entire contact patch is actually being carried on about 25% of the "contact patch" area. So the contact pressure of the tread block against the surface is actually more like 40psi.

To further the uncertainty, every tire size and tread pattern has a different void percentage.



That's why this whole thread makes no sense. It would have been much more informative and useful to ask "What tire pressure do you run for different terrains?"

Thanks!! I get what you're saying now.:awesomework:

 

[Skid Mark]

ummm you ever tried to use chaulk in mud? or snow?

I know fully what you are asking, but I dont think you fully understood by question.

I know that on differnt terrain you run differnt pressures. My question was how are you going to measure the contact patch in softer soil over concrete. If your rig is parked in mud or on mud right now. You are going to have a much differnt contact patch then if you move the same rig to concrete a few feet away.

Agian I assume most people intelligence is higher then a fifth grade level. I didn't say do it in the mud or snow and chalk was just one way of "marking the ground". just do it how it sits in ur driveway or trailer as prepared to go... Not complicated and again I'm looking for an average..

Ur lame

Please refer to last statement

This thread brings the suck!:BJ:

My 2yo. can spell better than you.:Ironsheik:

Wow ur two year old is smarter then alot of people. She obviously gets that from her mom.

I'm not sure exactly what "ground pressure" means. Not because I don't understand the forces involved, but because it's not a real term. My interpretation of Skid Mark's original post seems to indicate that it's the weight of the vehicle (at each tire) divided by the contact patch area. My assertion is that you could save yourself a lot of drawing, measuring, weighing, and calculating by just using a tire pressure gage.

Here's why: the pressure inside the tire is (more or less) equal to the pressure outside. It's not exact because the stiffness of the tire carcass and the shape of the tread at the shoulders may affect the uniform deflection of the tire, causing non-uniform pressure within the contact patch. It's not perfect, but it's a lot more accurate than chalk on the ground.


I'll explain a little bit more explicitly what I'm saying using bits from your scenario and some make-believe numbers. We have a Zuk and Burb, both on 33x12.50 BFG MTs at 10 psi. For simplicity's sake, they both have a 50/50 weight bias. Each tire of the Zuk has a downward force of 750 pounds. Each tire of the Burb has a downward force of 1500 pounds.

Using those numbers, the contact patch of the Zuk's tire is 75 square inches; the Burb's is 150 square inches. The contact patch must be twice the size because the force is doubled, but the pressure (which is measured in force/area) remains the same. If you built a device to measure the weight over a 6"x6" area under the contact patch of each rig's tires, it would read the same weight for both rigs (roughly 360 pounds).

To extraploate further, I'm guessing the BFG MT's tread pattern to be about 75% void space, which means the weight distributed over the entire contact patch is actually being carried on about 25% of the "contact patch" area. So the contact pressure of the tread block against the surface is actually more like 40psi.

To further the uncertainty, every tire size and tread pattern has a different void percentage.



That's why this whole thread makes no sense. It would have been much more informative and useful to ask "What tire pressure do you run for different terrains?"

You my friend have in no way understood anything. And have for some reason try to complicate even the most easy of calculations.. Ground pressure not a real word..?? You are obviously a web wheeler or just misinformed misguided misdirected person. Question did you even try to understand or did you prejudge the question because who asked it.. Your tire psi statement is so far off from the reality.. to use tire psi you must factor in sidewall rigidity as you mentioned and the entire surface of the inside of the tire and thats when things get complicated. and no the pressure out side is not the same as in side that is just dumb and a funny RFQ
To extrapolate further.. lol I touched on the difference in soft and hard soils and how that along with tread patterns will change the Exact amount.
This cracks me up You are one of those people that overanlizes thing and trys to confused your self along with others.. Its pretty strait forward

 

[Jay W]

You're assuming that there are people here who have a rig with tires on it to do all of that.

My jeep has the tires on it. They are just starting to touch the grass in the front yard too. Mainly because the jackstands are sinking into the grass. So my ground pressure at the tires is right about ZERO.:flipoff::redneck::flipoff:

 

[Boonie Buster]

This cracks me up You are one of those people that overanlizes thing and trys to confused your self along with others.. Its pretty strait forward

Explain please. :corn:

 

[Skid Mark]

Explain please. :corn:

:haha:

OK instead of copy and pasting a prior statement, I will say Ive explained it. If you have a specific question copy and paste you reference material and explain your lack of understanding and I will try to reiterate it in a different format so maybe your outdated version of perspective can be updated via the web

Modern tecknoligy... Bring out the intelligence of ignorance

 

[Ty.]

Now I'll admit I'm getting confused. It seems however like 64FJ40 is pretty close to being a good enough way, as tire stiffness wouldn't seem to have much of a measurable effect overall unless your running 988 loader tires. Some day I'll weigh the Jeep, and do your calculations, and see how that balances out to the tire pressure.

For the record I like this thread. More info. is always good