I want to build my own Sub-tank system

[TheJunkMan]

i have a 02 kx 250 I have only changed the springs for m weight to get the proper sag, valveing is stock, oil level is stock. Would it be benificial to add some sub tanks to the stock system for a softer more proggressive slow speed feel? Now the tricky part I have some resevoir chambers I five finger discounted from the local dump/junkyard, they are off of two early 90's yz (identical) I have no idea the volume (yet) of these chambers but i was going to make/buy fittings and braided hose to adapt from the chambers to the fork air bleeders. Is it worth it with stock vavleing. Are the fittings i will use for the bleeder screws going to be to small and restrictive? I have not thought of a way to make them adjustable (air restriction) I know that the ENZO sub tanks you have to drill out the air bleeder screw holes to a bigger size, I really do not want to do that to my fork caps. what do you guys think of this idea.

It is one I have been thinking of doing for the sake of seeing if it will work.

 

[Jaybird]

You want to make sure you aren't restricted by your fittings. The oriface of your fittings need to be as big as the largest setting of your restrive device. Which, btw, needs to be an in-line flow control.

This is going to make it so you have to drill out the bleeder holes. They are just too small and restrictive. Hard to find fitting of that size that will be suitable anyway. Its simply a drill and tap process...just make sure you have some plugs with o-rings to go in if the plan doesn't make it to completion.

On flow controls...many you find of that size will have an adjuster that is not notched in any way. What you want to find is an in-line flow control that adjusts in notches or "detents" that way you can stay consistant on both sides for adjustments.

Another thing you want to do is make sure you have some sort of evacuation on the bottom side of your new tanks. A petcock would work, but a Shrader valve would be better. You want to be able to get any oil that gets in there out easily.

They will work.

 

[jmics19067]

with no knowledge of fluid dynamics these are the things I would ask myself and work on.

does the air spring have to be bigger tha what you like.IE if you like your fork oil set low for a particular bump absorption and set high for another type of bump does you sub tank have to be bigger than that displacement of the air spring.I would guess not

At what point will the hose be restrictive? there is no need for a large easy flowing hose if you are going to be closing it off with a tapered needle or some other type restriction device. If by dumb luck a hex head main jet threads into your air bleed screw you might be able to try out the idea by just clamping some hoses and a filter to the end. There will be NO air spring at slow suspension speeds so be careful testing but you just might be able to feel if the hole is going to be too restrictive.


wondering how bad I am going to get reamed out for suggesting trying out an opened no airspring fork, and wondering if you actually need an airspring at slow suspension speeds if you can tune out bottoming with hydraulic bottoming cones or some other device. Aside from high maintenance of impurities contaminating the forks would there be an actual safety issue of instead of trying to tune your airspring, eliminating it? After all with sub tanks and/or low oil hieght arent you trying to lessen the airspring effect?

I am ready to get blasted by those that truly know suspensions,just trying to "think outside the box"

 

[TheJunkMan]

Come on suspention guru's I need some info here on the fluid dynamics. tell me some pros and cons, what it will do to and so forth I see the pros use them sometimes so they must have some value.

 

[mop]

JUNKMAN:
The subtanks work by manipulating the air spring created by the oil level volume and the subtank volume. The combined volume of BOTH these volumes is what compresses during slow speed, but as the compression speed of the fork increases, the restriction between the volumes allows only the oil level volume to compress. So the system does not work by hydraulic flow (oil), it works by air flow. The faster the fork compresses, the higher the oil level will feel.