Suspension while hauling.

[Mihylo33]

That just gave me an idea....

Lets say you have a 100 cubic inch (air tight) container that's filled to 50 psi. If you compress this space to 75 cubic inches, wouldn't the psi rise? So by compressing your forks aren't you also raising the psi as there's less volume?

That is an excellent question...
fill an air tank with 70 PSI now see if you can inflat a flat car tire to 35 psi and still have 35 psi in the tank... I tried it once a hundred yrs ago or 1990something... I still had a pretty flat tire... it worked on paper

 

[James]

That is an excellent question...
fill an air tank with 70 PSI now see if you can inflat a flat car tire to 35 psi and still have 35 psi in the tank... I tried it once a hundred yrs ago or 1990something... I still had a pretty flat tire... it worked on paper

Huh, not sure how that relates to what I was saying.

Ok you have an air tank with 70 PSI of air in it......don't let any air out of the tank but shrink the tank to half it's size (volume), would it still be 70 PSI?

 

[James]

fill an air tank with 70 PSI now see if you can inflat a flat car tire to 35 psi and still have 35 psi in the tank... I tried it once a hundred yrs ago or 1990something... I still had a pretty flat tire... it worked on paper

Ok now you have me thinking about this. Wouldn't this be more dependent on your tank size? For example a tank the size of your fist is obviously not going to fill up your tire. However what if the tank was a 1000 gallons?

 

[SRAD97750]

http://en.wikipedia.org/wiki/Boyle's_law

 

[Mihylo33]

Huh, not sure how that relates to what I was saying.

Ok you have an air tank with 70 PSI of air in it......don't let any air out of the tank but shrink the tank to half it's size (volume), would it still be 70 PSI?

I would think theoretically, no..... it should increase to like 92lbs...
...

 

[yamadogyz]

That just gave me an idea....

Lets say you have a 100 cubic inch (air tight) container that's filled to 50 psi. If you compress this space to 75 cubic inches, wouldn't the psi rise? So by compressing your forks aren't you also raising the psi as there's less volume?

Exactly! This is why factory yamaha maintenance tells you to put the bike on the stand before bleeding the forks. If you have pressure on them and bleed them, they will spit oil and then vaccume down and mess everything up

 

[James]

http://en.wikipedia.org/wiki/Boyle's_law

Interesting, so there might actually be some truth to this? So by reducing the volume of your fork tubes (tightening them down) your pressure goes up?

I would think theoretically, no..... it should increase to like 92lbs...
...

Well according to Boyle's Law, it would actually be 140 PSI.

Using the image above as reference:

You have a 4 gallon tank with 1 PSI. Shrink that tank to 2 gallons and the PSI would go to 2.

 

[Mihylo33]

Interesting, so there might actually be some truth to this? So by reducing the volume of your fork tubes (tightening them down) your pressure goes up?

View attachment 7088

Well according to Boyle's Law, it would actually be 140 PSI.

Using the image above as reference:

You have a 4 gallon tank with 1 PSI. Shrink that tank to 2 gallons and the PSI would go to 2.

yeah.... what happens when when a piston reachs top dead center?.... it has decreased the amount of space by 95%(?) or so and increased the compression...

 

[SRAD97750]

SO, according to boyles law.

Imagine a fork tube is 5 cubic inches at atmospheric pressure (14.7)
Fully compressed it might decrease the volume by 2.5 cubic inches(half).

So your looking at 29.14 psia (14.7psig) inside pressing on the seal.
Seal is approx .5 square inch of surface area when you factor in flanges and actual exposed internal surface

So approx 7 psi pressing on each seal when fully compressed(tied down).
A party balloon requires 2.5 psi to be inflated...

 

[James]

SO, according to boyles law.

Imagine a fork tube is 5 cubic inches at atmospheric pressure (14.7)
Fully compressed it might decrease the volume by 2.5 cubic inches(half).

So your looking at 29.14 psia (14.7psig) inside pressing on the seal.
Seal is approx .5 square inch of surface area when you factor in flanges and actual exposed internal surface

So approx 7 psi pressing on each seal when fully compressed(tied down).
A party balloon requires 2.5 psi to be inflated...

Dan, you're just to darn smart.

So what's the verdict?

Tightening your bike down does in fact increase the pressure on the fork seals, which could cause them to leak prematurely?

 

[SRAD97750]

*PLAUSIBLE*
I have no idea how tight the seals hug the inner fork tube...
How would you measure that besides hooking a fork up to an air compressor, turning it on and run!

 

[James]

*PLAUSIBLE*
I have no idea how tight the seals hug the inner fork tube...
How would you measure that besides hooking a fork up to an air compressor, turning it on and run!

Hey I'm all for trying this. Better yet, call up Mythbusters.

 

[Mihylo33]

*PLAUSIBLE*
I have no idea how tight the seals hug the inner fork tube...
How would you measure that besides hooking a fork up to an air compressor, turning it on and run!

now is it a hydraulic seal or a pnuematic seal?

 

[Naturaledge]

I love this stuff

 

[SRAD97750]

Its a FLUID seal. Which incorporates ALL non degrading fluids. Air is fluid.