Re-filling 350x shock with nitrogen

[TES]

I had a local shop re-fill my shock with nitrogen yesterday. Should I notice a difference in pressure just by lifting up and down on the grab bar when it's full of pressure? Seems to me it made no difference. Can you always lift the back end up another ~6 inches after the shock rebounds?

[Mr. Richard]

charging the nitrogen won't make any difference ,,, all that does is pressurize the oil to keep it fron foaming up under extreme conditions,,, you either need to adjust the spring preload ,, or get a new spring,,,,

[Black Sheep]

Originally posted by kasey
charging the nitrogen won't make any difference ,,, all that does is pressurize the oil to keep it fron foaming up under extreme conditions,,, you either need to adjust the spring preload ,, or get a new spring,,,,



:shocked: :doh: :ugh: :thmbsdwn: :eek: :nono:


uh...ok...yeah right.


first off why was it recharged?

if it leaked out in the first place then it may have leaked out again.

the only time you NEED to recharge is after a oil change or rebuild.


for the record you can adjust a stock 350X spring throughout it's range and you won't come up with or solve 6" of sag. the whole shock only has 7.5" of travel. something else is amis.

[TES]

It was recharged because when I disassembled and extended the swingarm I thought I was going to rebuild the shock at the same time … I removed the nitrogen … since then I decided not to rebuild the shock at this time (wanted to get it running ASAP), therefore I need to put it back together and had it filled again. Based on this, there is a third time that you “NEED” to recharge.

Let me clarify what I’m talking about regarding the sag … image you walk up to the back of your 350x and lift up on the grab bar … do your tires come of the ground immediately?? … if not, you lift up the rear of the trike x number of inches prior to the wheels coming off the ground … shock fully extends, etc. That is the sag I’m talking about … I’m guessing on the amount of lift … how much of this is normal? I doubt all 350x’s immediately lift the tires off the ground when you lift on the grab bar.

[Troll]

Here you go;
http://www.3wheeler.org/vb/showthread.php?s=&threadid=13456&highlight=shock
:thumbsup:

[TES]

Thanks for referencing that thread Troll ... good information ... I'll have to go through that process.

[Mr. Richard]

uh...ok...yeah right.

THATS INTELLEGENT,,,, maybe you could explain what else the nitrogen charge does besides keep the oil under pressure. the oil volume changes in the shock boby when the shock compresses so it is forces the oil into the resivior the nitrogen acts as a cushion and also forces the oil to return to the shock when it is fully extended.... anyway thats what i was taught,,,, if thats WRONG maybe you could explain what it really is for.

[TES]

Without going through all of those measuring steps (I know it's not going to come out good), can someone tell me what the following measurements tell you. I'm assuming it likely needs to be rebuilt. Also, what type of "starting" adjustments should I have on the shock. (i.e. collar adjustment and both knob adjustments ... I don't have an owners manual just a service manual.) FYI, I'm 6' and 225lbs.

Measurements .... ok, take a look at the following pic ... when I get off the trike and measure the distance between the ground and the bottom of my PRM Rack tube it measures 26.25 inches. If I lift up on the PRM Rack and then measure again I get 29 inches. Is this 2.75 inches of "resting sag" the sign of a worn out shock or a poorly adjusted one?
http://350x.home.comcast.net/x6.jpg

[Mr. Richard]

being 225 lbs i say you might need a heavier spring since you extended your swingarm,,,, you could try more preload,,, adjust the threaded rings down maybe 1/2" and see if that helps a little,,,, the knob on the canister is for dampening adjust ,, it won't affect sag,,, the way i would do it is screw it all the way in and ride a familuar trail ,, then screw it the other way and do it again ,,, that way you can kinda get the feel of the difference ,,, there is also one on the bottom of the shock too,,, PLAY with them,,, thats the only way you will get to see what difference they make,,,,,,

[Black Sheep]

Originally posted by kasey
the knob on the canister is for dampening adjust ,,

the knob is for "COMPRESSION" Dampening adjustmt.

thier is also a "REBOUND" Dampening adjustment.

[Black Sheep]

Originally posted by TES
Without going through all of those measuring steps (I know it's not going to come out good), can someone tell me what the following measurements tell you. I'm assuming it likely needs to be rebuilt. Also, what type of "starting" adjustments should I have on the shock.

TES, all thouse measurements tell you what your asking.


RACE SAG = how much the Trike sags with the rider aboard.

FREE SAG = how much the Trike sags under it's own weight.

both are measured differances between fully extended.

to determine if you have the right pre-load and/or proper rate spring for you and your trike you need to set the RACE sag first.

once that is set you measure FREE sag.

if you can't get the proper RACE sag AND FREE sag within the adjustment range of the spring you need a lighter (or in your case probably heavier) spring rate.

your Trike (350X) should only sag 3/4" to 1" under its own weight.

it (350X) should sag between 2 3/8"- 2 5/8" with rider aboard.


I would agree with Kasey's conclusion that you need a heavier spring. at 225lbs. your at the maximun limit for the stock spring. by adding a longer swingarm your increasing leverage. that alone requires a heavier spring in itself 90% of the time.

give "WORKS" performance al call. tell them your height, weight, type of riding, your machine, the swingarm extension ( they know stock ), and they will tell you what rate spring you need.

[TES]

TES, all thouse measurements tell you what your asking.
Yes, I know they would, yet my wife is traveling on business and my 4 mo. old daughter won't be able to measure while I'm sitting on the trike.

Thanks for the additional information ... you're confirming what I thought. I'll look "WORKS" up on google and get in touch with them.

[Black Sheep]

Originally posted by kasey


THATS INTELLEGENT,,,, maybe you could explain what else the nitrogen charge does besides keep the oil under pressure. the oil volume changes in the shock boby when the shock compresses so it is forces the oil into the resivior the nitrogen acts as a cushion and also forces the oil to return to the shock when it is fully extended.... anyway thats what i was taught,,,, if thats WRONG maybe you could explain what it really is for.

ok here you go...

there are 2 basic types of shocks

1. oil damped

2. oil damped with gas assist

the shock we are refuring to is a oil damped/gas assist.

what is the differance?

the oil damped shock use's the oil to control the speed of the shocks movement up and down and relies on the spring to provide the resistance and rebound.

if you were to take JUST the absorber on a oil damped only shock with the spring removed you could easily compress the shock with your hand and it would not come back on its own.


the oil damped/gas charged shock use's the pressurized gas (in this case nitrogen) to provide additonal compression AND rebound and relies on a softer spring rate then what would be used on a oil damped only shock.

if you were to take just the absorber on a oil damped/gas charged shock with the spring removed it would take some seriouse pressure to push with your hands if you could push it at all. and, if you could push it down with your hands it would imediatlly return out on its own.

the advantage of oil damped/gas charged shocks is that by using gas to controll what normally a stiffer spring would is a smoother and more controlable ride/action and the use of a softer spring rate which gives you a soft ride on small bumps yet can handle big hits as well.

[Mr. Richard]

the subject is a 350x rear shock,,,,, it has a nitrogen reservior ,, all the nitrogen does is pressurize the oil,,,,,,,, to eliminate the possibility of cavatation in the shock which causes foaming of the oil,,,,

you say this shock is gas assist.. ok where does the gas for the assist come from???? there is a bladder in the resevior to keep the oil and nitrogen seperate,,, so you will have to explain how this captive nitrogen assists the compression and rebound .

[Black Sheep]

first of all do you know how to rebuild shocks? ;)

your on the right track in your thinking but the gas is not thier to simply stop the oil from foaming. you actually answered your own question.


..." the oil volume changes in the shock boby when the shock compresses so it is forces the oil into the resivior the nitrogen acts as a cushion and also forces the oil to return to the shock when it is fully extended"...


without the gas pressure the oil would return only by the rebound from the spring and internal vacum pressure.

with the gas it forces the oil to go back quicker thus providing better action.


try this experiment if you have a spare shock lying around


remove the spring and try to compress just the absorber.

then remove the gas through the valve and then try to compress the absorber.

[FireHead]

I would like to point out that Kasey is right on the money when it come to what the nitrogen does in a shock. I would also like to add that nitrogen compresses at an exponentially rising rate, as opposed to air, which compresses linearily. The other reason nitrogen is used is that it is non-corrosive.

Mr. ATC has an a few interseting ideas about suspension design and technology. First of all, there are more than two basic types of shock absorbers. Assuming we are talking about coil-over shock absorbers on trikes, spring rate refers to the amount of pressure the spring will exert when compressed X number of inches. The major malfeasence occurs in the statement, " the oil damped/gas charged shock use's the pressurized gas (in this case nitrogen) to provide additonal compression AND rebound and relies on a softer spring rate then what would be used on a oil damped only shock." This isn't true. The only shock that makes this possible that may popularly be recognized are the FOX Air Shocks. If it were true you wouldn't see pretty aluminum reservours on the shocks, they would be steel or a metal matrix composite. Based on the principles of what was stated, if you put a higher pressurized nitrogen charge in your shock, it would increase the spring rate. That ain't right. It would stay the say to the effect it would change the shocks reactivity, as in make the shock more sluggish.


:shocked:

I think I may have came off like I was being an *******. Sorry Mr. ATC. I'm too lazy to retype it though.
:thumbsup:

[Black Sheep]

hmmm ok i'm lost what did you just say?

and i ask you the same question

do you know how to rebuild a shock?


i'm very well aware of air shocks. what i ment was two BASIC types of shocks. i was not refuring to EVERY type of shock.


lets simplify this.


inside a shock is a piston and valves. ( we won't get into shim stacks) the valves have little holes in them that alow oil to flow through. how fasdt or slow determines the rebound and compression of the absorber. as well as oil weight.

a lightweight oil will flow faster then and heavier oil.

oil will flow through a large hole faster then a small hole.

this is why you have compression and rebound adjustments. they alter the holes size to alter the flow.

now what role does gas play?

it forces the oil to flow rather then rely on it doing itself ( the oil)

this in effect alows the use of a lighter spring rate because by forcing the oil to flow faster the shock moves faster thus not reliny on spring pressue (as much) to extend the absorber.


here are some questions for you two suspension experts.

explain "high speed" dampening.

explain "high speed" compression.

explain "low speed" dampening.

explain "low speed" compression.

what is a valving stack?

what are shims?


finally look at the pictures of my works shock compared to my stock 350X shock and ask yourself why the works has a lighter spring rate. then give me the answer

[FireHead]

I know how design a shock, and I know how to rebuild them.

The FOX Air shocks are not like either oil damped or or nitrogen charge shocks. Therefore, there is another catagory, and what about the electromagnetic shocks foung on some Cadilacs and Buicks. I could go on.

If you increase the density of oil then you increase it viscosity. Therefore if you compress it, it's viscosity number increases.

THe nitrogen keeps a constant pressure on the oil to prevent airation(sp?) which leads to incosistant dampening. We must not fool ourselves into thinking htat shocks do anything think besides dampen the springs oscillations. Without a shock you would go down the road like a pogo stick.

The compression and dampening questions are all sort of related, on most ATV shocks, you adjust a knob which opens or closes and orifice in the shcok or resevoir, which essentially limits or increase the shocks sensitivity. Some shocks have high and low speed adjustments, which basically means it has two oricifes the control the smae properties in differant locations, whcih leads them to affecting the shock at differant piston speeds. SOme shocks have set valving or automatically adjust ing valving with no external adjustment.

The valving stack lives above the piston. They are all different. Could be a series of check balls or offset spring loaded discs. All they do is control oil flow past the piston.

Shims are pieces of materials used to separate or space something apart. They are usually of uniform, graduated thicknesses. They can be used for a few differant things in shock absorbers. I won't answer to that until you tell me what you want to know about to avoid confusing something I already said.

Your Works probably have a lighter spring rate because you ordered them for your weight. Fewer turns doesn't necessarily mean less of a spring rate. This is a really crappy example by the way.

:yup: :yup: :yup:

[ATCnut]

The gas in a gas charged shock may or may not provide additional spring force. It depends if when the shock is compressed the gas is also compressed, or if the gas is allowed to move to replace the oil.

I think we all agree that the oil is forced through an orifice, which can only happen at a slow rate, that is what causes the shock to move slow.

If the gas can also move from the two sides of the oil orifice, then the total volume of the system would stay the same, and the gas would not be additonally compressed by the movement of the shock, and would provide no additional spring force.

If the gas is only on one side of the oil, such that when you compress the shock, you reduce the volume of the gas, then the gas provides force just like the spring.


Firehead

I have to disagree about Nitrogen compressing expodentially and air lineraly. Physics says:

pv = nrt

p is the pressure

v is the volume

n is the number of moles of gas molucules (the physics way to meassure the actual amount of the gas, is proportinal to its weight)

r is planks constant (makes the units in the equation work out)

t is the temperature

All gasses obey this relationship.

I am also confused about why aluminum resivors would not work?

You can determine if a shock has the gas providing spring force by compressing it without the mechanical spring. If the shock will not stay compressed when you let loose, then the gas is providing spring force. If you compress the shock without the spring, and it stays compressed, then the gas is providing no spring force. Another way would be to measure the gas pressure when the shock is extended, and when it is compressed. If it changes, then the gas is being a spring.

If I remember correctly when I had my 350X shock apart, it would not stay compressed.

Both the gas and the mechincal spring obey the spring equation:

f = kx

f is the force generated by the spring

k is the spring constant
x is the spring displacement.

The initial pressure of the gas is the same as the preload on a mechanical spring.

The resivor adds to the volume of gas. this makes the spring constant of the gas lower.
The area that the gas is pressing on also effects the amount of force that it generates. This also effects the spring constant of the gas

The volume that the gas changes is the spring displacement for the gas. The resivor size effects the volume change, so it also effect the displacement value.

There is a lot of math here, I have not put it all down on paper.

IMHO the gas does provide spring force.

[FireHead]

I mis psoke about the compression of air. That wasn't what I meant to say. Just because your shock extends after you push it in does not mean that the shock is working to alleviate the work load of the spring. THe shock extending by itself is just a by-product of the gas charging. It has nothing to do with spring rate. Anyone who incorporates the force of the charge of the gas over hydraulic shock absober design, in a spring rate specification is an idiot. The reason there is a resevoir is to make the main shock smaller and to still allow for the necessary volume of gas and oil. Most shocks do not have resevoirs.

To put it another way, most non performance shocks have a closed cell foam that does the same thing as the gas, just not as well.

What I should have said was that the gas charge does not effect the spring rate. That's it. I think I confused everyone else including myself with the earlier posts.

If you want to talk about 350X shocks then that is a whole other issue and maybe thats what we should have been doing in the first place.


:thumbsup:

[Mr. Richard]

:eek: :eek: :eek: :eek: :eek: you guys really said a mouth full!!!!

[Dan10]

May I be excused please, I think my brain is full. ;)

[Black Sheep]

Originally posted by FireHead
I know how design a shock, and I know how to rebuild them.

The FOX Air shocks are not like either oil damped or or nitrogen charge shocks. Therefore, there is another catagory, and what about the electromagnetic shocks foung on some Cadilacs and Buicks. I could go on.


THe nitrogen keeps a constant pressure on the oil to prevent airation(sp?) which leads to incosistant dampening. We must not fool ourselves into thinking htat shocks do anything think besides dampen the springs oscillations. Without a shock you would go down the road like a pogo stick.


Your Works probably have a lighter spring rate because you ordered them for your weight. Fewer turns doesn't necessarily mean less of a spring rate. This is a really crappy example by the way.

:yup: :yup: :yup:


1. like i said before i am talking about 2 BASIC types of shocks NOT ALL CATAGORIES.

2. who's fooling who? your reading way more into what i am saying. CONSTANT PRESSURE is what i was talking about. this pressure forces the oil through its passages better then it would by itself. which would normally be acomplished by the vacum effect when the spring rebounds. therfore the gas is ASSITSING the oil and spring like i stated. and it is NOT JUST FOR ANTI FOAMING REASONS as preveously(sp?) stated at the begining of this debate. also a SHOCK is like the one mentioned in this debate (350X) is a combination of a absorber and a spring. without the absorber you would bounce like a pogo stick. the absorber danpens the Spring oscillations not "htat shocks do anything think besides dampen the springs oscillations."

3. this was a TRICK question. ;) :yup: :loser:

the 350X shock (like the one this thread is about) has a progressive rate spring. therefore no preset spring rate like the "Works" shock.


..."If you want to talk about 350X shocks then that is a whole other issue and maybe thats what we should have been doing in the first place."...
:doh: :doh: :doh:


it is good to debate with someone who at least has a clue about the subject.

not like some people who get to bat and strike out ( the mighty ***** struck out again) becuse they have NO CLUE and only like to argue with me because i'm me;) ;) ;)

[Mr. Richard]

:lmao: :lmao: :lmao: :lmao: :lmao: you can't even see the difference ,,, i am merely in search of information thats why i keep asking questions,,and waiting for answers,,, can you see anywhere i have said your wrong??????????????? i am gathering info,,,, ( nice pun ha ha ha strikeout lol you crack me up)

[Black Sheep]

hmmm;) :rolleyes: :cry: was i refuring to you:confused: :confused: :confused:

yes i see your point but your questions are more in the form of argumentative then searching.

[Red Rider]

Jeez, if I didn't know otherwise, I'd have thought you two were married to one another. You two argue more than my parents! :chuckle:

Can't we all just get along? :)

[Mr. Richard]

if i haden't said anything in this thread you wouldn't have all this wonderful information to read,,,,,,,,,,,,,,,,,,,,,,,,,, alot of things would just die if someone doesn't speak up!!!! so i choose to explore all possibilities and you all benifet:D :D :D

[FireHead]

I personally like to argue about things. Especially if its something I know alot about and think I am right.

:booty:

[turbo]

one thing i noticed that i would like to point out, Firehead, in your refference to Fox shocks, many of them work the exact same way as a 350x's, without the reservoir, they are still filled with nitrogen, and without the nitrogen, they will not "come back up" so to speak, im talking just the shock, not the spring also. with nitrogen, they will come back up. infact, there is no difference in the actual make up of a shock with a reservoir, and one without, the principles are the same.

[FireHead]

All of Fox shocks work like gas over hydraulic shocks except the Air Shox. THe Air Sox allow you to run with or without a mechanical spring, thus using a separate chamber of Nitrogen for the spring. They have version of these that are 10 way adjustable that have shraeder valves all over them for changing pressure in different chambers.

I think I said that there is no difference between the shocks with remote resevoirs and without them previously in this post, but as I am lazy I am not going to look back thorough it. So if I didn't, I shall say it again now. There are two reasons for remote revevoirs to allow heat another avenue to be removed from the shock and that if you wanted to you could mount the resevoirs very low on the chassis to get your center of gravity down.

[Black Sheep]

Originally posted by FireHead
I personally like to argue about things. Especially if its something I know alot about and think I am right.

:booty:


you even like to argue when your wrong.:lmao: :lmao: :lmao:


turbo is right. the resevoir has nothing to do with the nitrogen it is for oil. thier are gas charged shocks without resevoirs

[FireHead]

I am pretty sure I haven't said anything worng yet in this post anyway. I don't even know what the hell we are talking about anymore. THerefore I quit in confusion.

However I would like to point out that I am a genious. Just ask me.

:thumbsup:

[Black Sheep]

Originally posted by FireHead


However I would like to point out that I am a genious. Just ask me.

:thumbsup:


are you a genious

[ScottZJ]

Well rebuilding a shock involves more than just recharging, oil and gaskets. The main thing you should look at the the spring strength and the shaft. If the spring is shot then all the oil and recharging in the world wont do any good and if the shaft in the middle is scored at any place, it will just tear up the nice new gaskets that you just replaced. When rebuilding a shock, you basicly replace all internals and the only thing you have left is the shell(if its in good shape). Almost worth calling the shock pros in Caliy and custom make you one..............peace

[ATC250R84]

are you a genious

hahahaha, man mr. atc, your like the smart as$ of all smart a$$ess, LOL, that is just funny!!!, but i just wanted to tell you, i want that 250r carb boot, but everytime i try to PM you, it tells me your PM box is full and it wont let me send, please check it out and empty it or whatever. :)

[Black Sheep]

try it now

[TES]

ScottZJ wrote: "Almost worth calling the shock pros in Caliy and custom make you one"

Agree, that's what I've done.