Ground pressure poll

[Binder]

Well I'm going to go out on a limb here and say that with all the users on this board I would be VERY suprised if there were more than 5 that could figure out the surface area of a elipse which would be needed to do this.

Pi x A x B

 

[Boonie Buster]

Holy cow. Do you really believe this? Why do you think the footprint changes size with different internal air pressures?

It also changes with more/less weight applied to it. so then it can't soley be air pressure...

 

[Boonie Buster]

Well I'm going to go out on a limb here and say that with all the users on this board I would be VERY suprised if there were more than 5 that could figure out the surface area of a elipse which would be needed to do this.

Pi x A x B

Agreed! :haha::haha::haha:

and it's not really an ellipse youre trying to get the area of.... :eeek: its more of a circumfrance and width and percentage of area touching the ground of that circumfrance...:redneck: for the touching of the thingy to the groundy to makey the build up of the air stuff in the rubber thing.

-----> = :stirpot: confusing babbling math nonsense theory to make more NWWers think they know more!

 

[crazybluerider1]

I'm pretty sure that ol' skid mark confused himself back on page one.

This thread is dumb.:eeek:

 

[Jaydog]

Well I'm going to go out on a limb here and say that with all the users on this board I would be VERY suprised if there were more than 5 that could figure out the surface area of a elipse which would be needed to do this.

Pi x A x B

You're probably right, even though it isn't any harder than finding the surface of a circle. :redneck:

 

[CHOP SHOP]

Well I'm going to go out on a limb here and say that with all the users on this board I would be VERY suprised if there were more than 5 that could figure out the surface area of a elipse which would be needed to do this.

Pi x A x B

Thats a very small step in this equation. (says dumb dropout) :beer:

 

[Binder]

Thats a very small step in this equation. (says dumb dropout) :beer:

Yeah I know but I don't feel like drawing pictures.:redneck:

 

[64FJ40]

First you are trying to create one equasion with two problems YOUR TIRE PSI HAS NO EFFECT ON GROUND PRESSURE OTHER THEN CONTROLLING THE SIZE OF YOUR FOOT PRINT.

No. You are trying to separate one thing into multiple components and then pretending that those components aren't related.

From wikipedia:
Ground pressure is the pressure exerted on the ground by the tires or tracks of a motorized vehicle... Ground pressure can be calculated using the standard formula of pressure: P = F/A (object's weight divided by contact area)

Ground pressure is equal to the weight divided by the area. That's what you insinuated with your measurement procedure at the beginning of the thread. That's fine. The part that you seem to disconnect from that equation is that the area in that formula is determined by the air pressure in the tire. Of course it controls the size of the footprint. That's because the area of the footprint is the only area of the tire that is able to transmit a force to the ground.

From this article:
"lowering pressure will raise the coefficient of friction by reducing contact patch pressure and increasing the size of the contact patch."

Maybe you should go write on the NHRA website and tell them tire psi has no effect on your tire foot print I'm pretty shure they would want to know they been doing it wrong since they started.

Your lack of understanding (and consequent misinterpretation) of what I write doesn't make me any less correct. I never said that.

Did you really go to the NHRA website to research for this? That was the most reliable source of empirical information you could think of?

Let me explain..
your tire is round
The psi in the tire is pushing on ALL sides of the tire
The top of the tire has the same pressure inside as the bottom.
that cancels out the first number in your equation
10 pounds of pressure pushing down and UP

You're partly right. The problem with the way you're thinking about it is that the air pressure along the entire outer surface of the tire isn't in contact with anything that it can exert a force upon except for the contact patch at the bottom. The tire isn't pushing UP on anything. Force is a vector. Vectors have magnitudes AND directions. Lacking either of the two, it's not a force.

The tire it self is the only thing holding the weight
the tire pressure is what gives the rubber tire its ridgidity to support the weight
the weight goes from the axle to the rim to the tire and the ground
Not axle rim AIR tire ground

Again, partially correct. And again, the problem is the way you're thinking about it. If the air's only purpose was to maintain the sidewalls' rigidity, then all of the force holding the vehicle up would be right at the edges of the tread, at the sidewalls. But it isn't. The air pressure inside the tire creates an equal surface pressure across the entire tread surface.

You are wrong sir and you don't want some poor person that has less education then you making you look stupid I understand that.

Why do you keep implying that money or education level have anything to do with this? You don't know a thing about me except what you've seen online. Your unfounded assumptions do, however, reveal a lot about you. Please be so kind as to leave personal stuff out of here.

 

[64FJ40]

I did some research to prove my point and wow I found a forum with a similar discussion. I thought if you read it some were else you might respect it. I stoled this from IH8MUD.com but you can go argue with theirs guys they have more smearts then this redneck :fawkdancesmiley:

Yeah I know those guys and am familiar with that thread. You may recall that I addressed tire construction aspects earlier, including carcass and tread.

There is a lot more to it, but it doesn't matter, because here's the kicker: those can only INCREASE the ground pressure above the inflation pressure. There is no mechanism that allows your tires, at 12psi, to exert only 6.74psi on the ground unless the ground is only capable of supporting 6.74psi (sand, snow, whatever) and IT conforms to the tires in order to increase contact patch.

So to sum up this thread, less ground pressure equals better traction. :awesomework:

Less ground pressure equals more flotation and a bigger contact patch. But not necessarily better traction, depending on the terrain. Tire pressure too low could allow too much carcass deflection under load, reducing the efficiency of tread block edges.

for the touching of the thingy to the groundy to makey the build up of the air stuff in the rubber thing.

:haha:

 

[82toyomud]

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

64fj40 "complicated" things because he understands how they actually work, and doesn't live in "idealized" world where rudimentary weight/surface area calculations can get you buy:looser:

And if you understood a basic FBD (Free-Body-Diagram) you would understand that 64fj40's tire pressure=contact pressure will get you a closer actual answer than your calculations will.

 

[Jay Luke]

A person who agrees with another for only to write negative comments about something he has no understanding

You are the failure

AWWW. i SO SAWRY:haha:

 

[wentz912]

Skiddy disappeared. And to boonie, you would have to find the surface area of an elipse because if a tire were truly, perfectly circular, it would only contact at ONE miniscule, infinitely small point. Since we know this is not the case, we can assume that one or more of our round(ish) shape's "sides" is longer than the others.

 

[Skid Mark]

No. You are trying to separate one thing into multiple components and then pretending that those components aren't related.

Funny thats what I said to you.. And I'm the one asking the question here

From wikipedia:
Ground pressure is the pressure exerted on the ground by the tires or tracks of a motorized vehicle... Ground pressure can be calculated using the standard formula of pressure: P = F/A (object's weight divided by contact area)

Ground pressure is equal to the weight divided by the area. That's what you insinuated with your measurement procedure at the beginning of the thread. That's fine. The part that you seem to disconnect from that equation is that the area in that formula is determined by the air pressure in the tire. Of course it controls the size of the footprint. That's because the area of the footprint is the only area of the tire that is able to transmit a force to the ground.

And again I covered this

From this article:
"lowering pressure will raise the coefficient of friction by reducing contact patch pressure and increasing the size of the contact patch."




Your lack of understanding (and consequent misinterpretation) of what I write doesn't make me any less correct. I never said that.

I understand what you have written I never said I don't understand you. I said your wrong.
I Ask a simple question to do some research and have a interesting perspective.
I ask for an average number understanding the level of precision we could establish if we took in to account every force pressure or even inersha if we were moving.. But I didn't ask for all that. I ask a simple question that gave a good estamit on the approximate psi on the ground
I said and explained there are variables but I was looking for an Average hell I even said make something up in the 3rd post.

Did you really go to the NHRA website to research for this? That was the most reliable source of empirical information you could think of?

Did I say I researched the NHRA.

You're partly right. The problem with the way you're thinking about it is that the air pressure along the entire outer surface of the tire isn't in contact with anything that it can exert a force upon except for the contact patch at the bottom. The tire isn't pushing UP on anything. Force is a vector. Vectors have magnitudes AND directions. Lacking either of the two, it's not a force.

Ya ok so we established you have "book smarts" Again I understand force I may also understand a little more then that. Its easy to play dumb and your playing smart and failing I didn't ask about this and if you feel compelled to write a bunch of long drawn out math equations your on the wrong board

Again, partially correct. And again, the problem is the way you're thinking about it. If the air's only purpose was to maintain the sidewalls' rigidity, then all of the force holding the vehicle up would be right at the edges of the tread, at the sidewalls. But it isn't. The air pressure inside the tire creates an equal surface pressure across the entire tread surface.

This is analization parlization
ok Ill play
Things in a tire that effect grund pressure
1 the weight of said tire and said car,truck,buggie,etc its bolted to
2 the size of said tire
3 the surface said tire is in contact with in conjunction with said tire tread design
4 The engineered design of said tires steel or nylon bys cords in inner of the tire
5 The chemical make up of said tires rubber composition
6 And last tire pressure.. No why its last
If a tire is properly inflated and of a steel belted design th psi accost the entire surface of the tires contact patch is a lot more constant.. but if you air your tire down as any one who has and driven accost dirt can tell you the side of tread pattern digs in more due to supporting a majority of the weight because of an decrease in air pressure the center of the tire squishes in under load...
If I wanted to get this specific I would of ask to have all those variables to be measured.



Why do you keep implying that money or education level have anything to do with this? You don't know a thing about me except what you've seen online. Your unfounded assumptions do, however, reveal a lot about you. Please be so kind as to leave personal stuff out of here.

No it has to do with your inability to keep it simple.

Yeah I know those guys and am familiar with that thread. You may recall that I addressed tire construction aspects earlier, including carcass and tread.

Not all the aspects

There is a lot more to it, but it doesn't matter, because here's the kicker: those can only INCREASE the ground pressure above the inflation pressure. There is no mechanism that allows your tires, at 12psi, to exert only 6.74psi on the ground unless the ground is only capable of supporting 6.74psi (sand, snow, whatever) and IT conforms to the tires in order to increase contact patch.

You are flat wrong.. Sad But I feel that even if I explain this to you again there will be a two page math equation confusing your self and he people Trying to understand how you can take something so simple and make it so complcated... Math don't lie and your math don't add up.. Heres a hint the 12 psi is CONTAINED



Less ground pressure equals more flotation and a bigger contact patch. But not necessarily better traction, depending on the terrain. Tire pressure too low could allow too much carcass deflection under load, reducing the efficiency of tread block edges.

Your correct wow. and this would of been great if it was the only thing you said. on certain terrains more ground pressure works better and I wanted to get a look at what people were running and what they wheel most of the time so when buying tires and debating size you could determine what tire would work for you preferred terrain by using the reference of vehicle and tire combinations of the people of the board


:haha:

64fj40 "complicated" things because he understands how they actually work, and doesn't live in "idealized" world where rudimentary weight/surface area calculations can get you buy:looser:

Wow you don't understand either one of us and just agreed with the last post

And if you understood a basic FBD (Free-Body-Diagram) you would understand that 64fj40's tire pressure=contact pressure will get you a closer actual answer than your calculations will.

I wasn't talking to you to when I said this earlier but I NEVER SAID I DIDN'T understand what he wrote except for the two or three things he has wrong.

 

[64FJ40]

I wanted to get a look at what people were running and what they wheel most of the time so when buying tires and debating size you could determine what tire would work for you preferred terrain by using the reference of vehicle and tire combinations of the people of the board

Post #14:

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?"

:hmm:

You are flat wrong.. Sad But I feel that even if I explain this to you again there will be a two page math equation confusing your self and he people Trying to understand how you can take something so simple and make it so complcated... Math don't lie and your math don't add up.. Heres a hint the 12 psi is CONTAINED

I'm making it complicated? It all makes perfect sense to me and we haven't even gotten to anything complicated yet. If you were paying attention, you would recall that I was the very first one to suggest that all of your measuring and dividing was making it way too complicated when all you had to do was grab a pressure gauge. But you didn't understand why that would be more accurate than your chalk-line method, so here we are.



I'm ready to be done with this. You?

So here you go: Explain a scenario that actually makes sense, where a tire inflated to 12psi, carrying some realistic load, can exert less than 12psi of contact pressure on a hard, load-bearing surface as you claim your tires are somehow able to do.

Until then, :corn:

 

[Skid Mark]

I'm ready to be done with this. You?

So here you go: Explain a scenario that actually makes sense, where a tire inflated to 12psi, carrying some realistic load, can exert less than 12psi of contact pressure on a hard, load-bearing surface as you claim your tires are somehow able to do.

Until then, :corn:

Jeep gvwr prepared (approx) 5500
Divided by
Contact patch is 816 sq in
=
6.74019608

I will give you this I do understand the equation you repeatedly try to insinuate was easier. But as we have both touch on there are a abundance of variables.
One of which is tire pressure gages... Evidently mine is off. I rechecked with three different gages I got a 10 psi average.
which still means your off and thats due to the lack of perfection in an equation of averages. It was never ment to be an exact since just a reference
At the same time you first accused me of making terms up "ground pressure"
second instead of doing it you just look for a flaw in my math instead of participating
Along with that the things you were explaining you nowhere and in noway touched on the entire subject and lets face it. It requires a more direct approach for discussing the technicality of force vectoring and other things related to mapping out the specific ground pressure per inch

The hole thing was relative to tire design and what sizes with what vehicles and an number to relate and compair with out getting technical

How do you say it ... Thanks again for making this more difficult then it need to be next time just put your numbers down and let people write what they want about there rigs


But ya good times :beer:

 

[Binder]

OK here's something for you guys to ponder...I run 3 PSI in my 42" swampers. This leaves a huge footprint..I drive one wheel onto a 2" diameter tree limb. Contact patch reduces greatly. Now is the air pressure still 3 PSI? Does that tire still support the same weight?..:corn:

 

[Skid Mark]

OK here's something for you guys to ponder...I run 3 PSI in my 42" swampers. This leaves a huge footprint..I drive one wheel onto a 2" diameter tree limb. Contact patch reduces greatly. Now is the air pressure still 3 PSI? Does that tire still support the same weight?..:corn:

Yes the air pressure is still at 3psi and its supports the same weight. 99% of it(not exact percentage 64fj40) is due to tire construction at that point

 

[boardbysled]

Well, if we want to get technical, there is some weight transfer to the other 3 tires:flipoff:

Also, your tire would then concave around the tree branch, increaseing your PSI in your tire ever so slightly.

 

[Skid Mark]

Well, if we want to get technical, there is some weight transfer to the other 3 tires:flipoff:

Also, your tire would then concave around the tree branch, increaseing your PSI in your tire ever so slightly.

:haha::haha::haha::haha:

 

[Binder]

OK here's something for you guys to ponder...I run 3 PSI in my 42" swampers. This leaves a huge footprint..I drive one wheel onto a 2" diameter tree limb. Contact patch reduces greatly. Now is the air pressure still 3 PSI? Does that tire still support the same weight?..:corn:

I don't ask this for my own information but as a attempt to get us all to think about this in different terms....Often times it helps me to think of things in extreme perameters and see how it "fits"..What if the tires were 30 feet in diameter and had 2 PSI? What if they had 1000 PSI? What if the tires were 2 inches in diameter with 1000 PSI? What if the rig weighed 10 pounds?
What if......
See what I'm getting at?