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Fork Pressure idea

  • Thread starter Thread starter cberkeley
  • Start date Start date
C

cberkeley

Guest
Bright Idea ?.but with my luck someone?s already done it.
Ok, My front shocks work fine as is. I maintain about 15-PSI therein and all is well. But I have to keep topping up and this takes time as it?s low pressure small capacity and just removing the pressurization fitting, vents enough air from the shocks to negate the effort in the first instance ?.a hassle at best.
So, Here we go:
Suppose I take out the two insets from the valves, Make a fitting that connects the valves to 1/8? pneumatic pressure tubing, the two air lines thus go to a ?Y? fitting, thence to a miniature air pressure regulator which sits atop a small pressure tank, which thus has the input top-up pressure fitting and possibly a water bleed (see my sketch). I can then set the regulator at my desired 15-PSI and just keep my main pressure reservoir (which can be a chrome plated and esthetically fitted small fire extinguisher envelope) filled at say 100-PSI.
What do you folk think??
View attachment 1309
 
Looks feasible. How often do you have to top off the forks? Why don't you fill the forks to the recommended psi and then use a soapy water solution in a spray bottle and liberally coat all the possible leak areas. It might be easier to find the leak and fix it instead of rigging up your modification. Ted
 
I agree with knotzilla, if you're just trying to fix a minor air leak this way it's like squashing a bug with a 10lb. sledgehammer...slight overkill. (but fun! Hard on the sidewalk, though.)

HOWEVER, one benefit of such a setup would be to allow you to adjust your fork pressure "on the fly", especially if you incorporate some sort of bleeder valve to lower the pressure. Also, you have the advantage of having a tank that, with some fittings, would also allow you to air up a low tire, etc. Not too much volume in those small tanks but it would help.

If you really want to trick out your forks instead of going through the minor hassle of finding a leak, think about searching the forum for articles on swapping out your front end with a Katana or something similar.

Definite congrats on coming up with an interesting modification, though. If you decide to go ahead with it, post some pics!
 
txironhead said:
If you really want to trick out your forks instead of going through the minor hassle of finding a leak, think about searching the forum for articles on swapping out your front end with a Katana or something similar.

Definite congrats on coming up with an interesting modification, though. If you decide to go ahead with it, post some pics!
Click to expand...
That or install Progressives and forget the air altogether.
 
I don't see the big problem with putting air into the forks, I dial down the impact guage on the compressor to about 25 and shoot air into my forks, check it with a guage and it is 15lbs which is right where I like them. My forks though are connected and only have one fitting so they are always balanced.


One problem I have is that I always get oil out of the fitting when I check the pressure so I have to use a mechanical guage rather than my electronic guage.
 
I agree with loosing the air altogether with a set of Progressives. My shocks are awesome with progressives, a 1 3/4" spacer and 15 wt oil. I'm about 250 and often ride as hard as the bike will allow me to.
 
I think the problem you might have with using a larger volumn air tank is that as the forks compress the air in the fork tubes the pressure actually rises a lot due the confined area. It kind of makes the suspension progressively firmer as the forks compress. If you increase the volumn you will lose most of this effect. I'm with most others here and just run progressive springs. I think Harley at one point actually used the crash bars as an air reservior, but the whole system was probably designed around it.
 
Apropreate regulators are cheap, and common. If you wanna have some real fun, I'd actually reccomend using co2. I'll

BUT.. You should look at the cause of the problem. if you're leaking down, that means you have a leak somewhere. I'm with everyone else here, and I'd reccomend going with progresives, or you can go my way and get rid of the gaurd springs and put in a peice of PVC in it's place.

If you go throgh with this.. this is the regulator you want. A Palmers Micro Rock. It's output is 10/32, the input is 1/8npt. https://palmer-pursuit.com/ecom/index.php/cPath/22_40?osCsid=9390a82dc0bafac8996415926f21e46a

At that point you'd just need a CO2 bottle, a bottle adapter, some microline, and some fittings to make it fit your fork caps. We'd be talking $150 total. At least if you're willing to drill and tap your own fork adapters. A 9oz co2 bottle would last you years.

The regulator I pointed out is designed for the Low pressure regulation of a paintball gun. The regulator has a lifetime warrenty, and if it ever fails, you can just send it back to palmers and they rebuild them for free. The reason I suggest the micro rock, instead of the rock is that the micro rock does not have a blow off valve. That way the air pressure loading in your forks will be able to do it's job instead of venting off.
 
cberkeley said:
Bright Idea ….but with my luck someone’s already done it.
Ok, My front shocks work fine as is. I maintain about 15-PSI therein and all is well. But I have to keep topping up and this takes time as it’s low pressure small capacity and just removing the pressurization fitting, vents enough air from the shocks to negate the effort in the first instance ….a hassle at best.
So, Here we go:
Suppose I take out the two insets from the valves, Make a fitting that connects the valves to 1/8” pneumatic pressure tubing, the two air lines thus go to a “Y” fitting, thence to a miniature air pressure regulator which sits atop a small pressure tank, which thus has the input top-up pressure fitting and possibly a water bleed (see my sketch). I can then set the regulator at my desired 15-PSI and just keep my main pressure reservoir (which can be a chrome plated and esthetically fitted small fire extinguisher envelope) filled at say 100-PSI.
What do you folk think??
View attachment 1309
Click to expand...

The issue most people don't realize with air, is that it HEATS up from sliding fork action friction. When air heats up it gains pressure. On a street bike the rise in pressure is only minimal, but when i race MX, I actually bleed off the excess pressure frequently.
I personally don't run any air.
 
Nerobro said:
If you go throgh with this.. this is the regulator you want. A Palmers Micro Rock. It's output is 10/32, the input is 1/8npt. https://palmer-pursuit.com/ecom/index.php/cPath/22_40?osCsid=9390a82dc0bafac8996415926f21e46a
Click to expand...

DUDE! I clicked that link and the security in my windows vista RC1 went nuts!

There is a problem with this website's security certificate.






The security certificate presented by this website has expired or is not yet valid.
The security certificate presented by this website was issued for a different website's address.


Security certificate problems may indicate an attempt to fool you or intercept any data you send to the server.

We recommend that you close this webpage and do not continue to this website.
Click to expand...
 
it's a completely legitmante site. They just havent' updated their certificates, and it's a buisness with oh... four employees. :-) WEbsite design is FAR from their top priority.

If you read the errors, they only say that the certificate is out of date. The certificate expired on 9/14/06. Woo, they're a little more than a month out of date. :-)
 
Last edited:
cberkeley said:
Bright Idea ?.but with my luck someone?s already done it.
Ok, My front shocks work fine as is. I maintain about 15-PSI therein and all is well. But I have to keep topping up and this takes time as it?s low pressure small capacity and just removing the pressurization fitting, vents enough air from the shocks to negate the effort in the first instance ?

Sounds like the dust covers are all that's holding the air in? Tighten or replace the tire valves if the soapy water proves them to be the culprit as mentioned by others.

I bought a very small gage only 25psi just for this purpose. I fill the shock with only the air remaining in the hose of my portable tank. Even the tiny capacity of the gage will drop 2-3psi so that has to be allowed for. When it reads 15psi and I take it off I will only have 12-13psi remaining. Supposedly the bikes originally came with a very small gage for this purpose. My original 81 shocks are still holding air fine. When I got the bike one shock was 30psi and the other was 12psi....oh well. At least it proves they can take more than it says is max:)

I would change the seals and oil before I would change the struts. They seem to be very reliable and cheap to maintain. Unless I could lower the bike a couple inches too:)
Click to expand...
 
nitrogen is exactly as compressable as any other gas. At 15psi, co2 is a pretty stable substance. At "normal" tempratures co2 needs 800psi to maintain a liquid state. At fork pressures co2 will always be a gas. Compressed air is a pretty dangerous thing (I can give you examples if necessary) however liquid co2 has several of it's own safety features built in.

First of all, co2 is stored as a liquid, and because of this requires a LOT of energy to change to a gas. The whole phase change thing ;-) So if your bottle ruptures, or is ruptured, it looses pressure very quickly. Being a liquid also gives you a nice "first level" of regulation. As bottle pressure is regulated by bottle temprature, you regulator will only see an input range of 600-900psi, instead of 100-15. Or more realisticly 1800-15psi, or 3000-15psi. Regulators have something called a pressure ratio, and as you vary the input pressure, the output pressure varies as well. So with a typical pressure ratio of 25:1, you'd see your fork pressure go from 15psi to 19psi throughout the discharge of your 100psi storage tank. Not a good thing.. The regulator I pointed out is 50:1 or better. :-) Though I think the ratios fall apart outside the "working range" of a reg.

Being stored as a liquid also means you get much more gas for a given volume of storage. If you need an example, a 13ci tank full of nitrogen at 3000psi only holds about 1/4 the energy of a 13ci bottle of co2, at 800psi.

Co2 is the best option. Even a 12gm cartriage would be able to keep the forks topped up for a very long time.
 
I dropped the air when I went to priogressive springs, before that I used a 5 gal air tank with a regulator I would set it at 8-10 psi & hit both fittings twice
 
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