Tire Pressure On A Lift And Off

[stator]

Is the air pressure the same off the ground than on the ground? Really?
A similar question would be "which is heavier - a pound of rocks or a pound of feathers?"

[Top Cat]

Originally Posted by stator

Is the air pressure the same off the ground than on the ground? Really?
A similar question would be "which is heavier - a pound of rocks or a pound of feathers?"

Is this a trick question
Everyone knows rocks are heavier than feathers.
That is why a rock will hit the ground before a feather if both are dropped from the same height at the same time

[seacliff]

The tire will bulge when on the ground ever so slightly, which allows for the same amount of surface area and thus the air pressure remains the same.

On shocks, and I started this war, is different. As someone stated as the air bladder decreases due to wieght the surface area also does which means less molesules on the surface area and thus a actual reduction in air pressure. If you place the bike on a lift the shock expands creating more surface area in the bladder, more molecules on the surface area and more pressure.

A simple way to test this is what I suggested and I have proven this now to many a folks. Use your Harley pump and pump one shock up to any pound setting, with the bike level and your ass not on the seat. Not put the bike on the sidestand and check the pressure again and it will be lower by about 7 lbs. So if you check the pressure on sidestand one shock is more compressed then the other and you end up with 2 different pounds of force and you can tell this by as I said, level bike with you not on it and check the pressures.

I found putting extenders on the valves and straddling the bike with my ass not on seat allows me to put air in each individual shock and this is about as close to equal as you can get. There is still force on the shocks and if I raised it up on a lift the pressure would increase by about 8 lbs.

So never max the pressure out with bike not on lift.

[seacliff]

Originally Posted by cnc

Gene I guess you mean the shock thread and yes there was / is a difference from weighted to unweighted. The bladder is contained with in the shock tube, so when weight is put on the rear wheel there is no place for it to bulge so it compresses and the pressure goes up.

actually pressure goes down due to less molecules on less surface area.

http://ww2010.atmos.uiuc.edu/(Gh)/gu...w/prs/def.rxml

[Top Cat]

Your saying if I put x amount of air in the shocks with the bike standing straight up with no weight on the bike then sit on the bike and the pressure in the shocks will go down.
I don't think so.

[ringadingh]

The pressure does go up.

[blowndodge]

Originally Posted by Top Cat

Your saying if I put x amount of air in the shocks with the bike standing straight up with no weight on the bike then sit on the bike and the pressure in the shocks will go down.
I don't think so.

He's saying if one puts x amount of air in the shocks the molecule of a penis you have will become even smaller!!

[seacliff]

TC, thats easy to dispute, but why not just try it and find out.

BD, I couldnt have said it better.

[Top Cat]

Originally Posted by blowndodge

He's saying if I put x amount of air in the shocks the molecule of a penis I have will become even smaller!!

You didn't have to admit it Brad. We knew from most of your posts you were trying to make up for a small dick.

Originally Posted by seacliff

TC, thats easy to dispute, but why not just try it and find out.

I'm sure I will sometime in the near future. The bike is in my unheated garage for winter.

[kenb]

Good bandwidth is a terrible thing to waste!

[blowndodge]

Originally Posted by Top Cat

You didn't have to admit it Brad. We knew from most of your posts you were well hung!



I'm sure I will sometime in the near future. The bike is in my unheated garage for winter.

Thanks tc

[VulcanE]

Originally Posted by seacliff

actually pressure goes down due to less molecules on less surface area.

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/prs/def.rxml

I read the above link, and in that scenario, yes the pressure applied on point X will decrease because the container is open to the atmosphere and you push the molecules out, so you have fewer molecules pressing on point X....BUT, in a shock (if the schrader valve is installed) the molecules can't escape into the atmosphere. As the piston collapses, the molecules are compressed closer together. You now have the same amount of molecules occupying a smaller space, and this increases the pressure exerted not only on point X, but in every direction, but point X is the only moveable point. With my rear wheel off the ground, I removed the schrader valve to let the shocks go to atmospheric pressure (I only have one due to the fact I have a balancing kit installed), then replaced the valve, then hooked up my shock pump (with a guage on it) to the valve and it read "zero". I then let the bike down and sit on the side stand and the guage read 7 psi. So, with the bike on the ground, compressing the piston (point X), it INCREASED the pressure by 7 psi. If you pump more molecules in, this will increase the pressure even more. This is all basic in fluid/pneumatic power.

[Yellow Jacket]

Originally Posted by seacliff

actually pressure goes down due to less molecules on less surface area.

http://ww2010.atmos.uiuc.edu/(Gh)/gu...w/prs/def.rxml

Your link is talking strictly about atmospheric pressure.

When we're talking about the pressure in an air shock we are talking about the pressure in an enclosed volume.

It's pretty basic science that when you have an enclosed air tight volume filled with a gas, if the volume is decreased without changing the amount of the gas in the volume, then the pressure will increase. Conversely, if the volume is increased without changing the amount of the gas in the volume, then the pressure will decrease.

Boyle's Law http://www.grc.nasa.gov/WWW/k-12/airplane/boyle.html

[Top Cat]

Hello, seacliff where are you? Hello.
Oh crap, did we make another member quit

[Sin City Stan]

Originally Posted by seacliff

actually pressure goes down due to less molecules on less surface area.

http://ww2010.atmos.uiuc.edu/(Gh)/gu...w/prs/def.rxml

Ah . . . no, it goes up. I tried it. We are not talking atmospreric pressure but air in a closed space. Take the same amount of air and put it in a smaller space and the pressure will go up no matter what size Brad's penis is.