I just changed the oil in my NR4!

[Luke]

It had leaked since the last time CVI serviced it, and filally the damping went completely last week.

I figured as I'll be buying one of those 8.125 ebay Swingers I can have a look inside the Noleen.

Pushed in the rubber nitrogen plug and unscrewed the nitrogen can. I messed up the anodising with a pipe wrench after much effort between nylon/wood blocks.

The shaft seal body just pushes in when there's no pressure, so you can get to the circlip no problem.

The oil was BLACK and heavily charged with something; don't know what as there was no wear evident in the cylinder.

I filled the cylinder up with nice clean oil and then screwed the air can on sealed with plumber's tape in the place of the pinched O ring. The floating piston almost completely out so that there's no air trapped in the oil.

Then the piston/ rod assembly goes into to the cylinder, overflowing oil and pushing in the floating piston. On with the circlip and time to think about the nitrogen pressure...

In fact the pressure is held in by a poxy rubber bung! I sharpened up one of those football needles that come with cheap car tyre compressors and stuck it through the plug in situ before screwing the air can on. The needle (that you normally end up losing in a few days) has the same thread as the shock pump!

Pumped up to 200 bar, pull the needle out and the whole thing works great.

Air/nitrogen... Phooey!
If I were to replace the rubber bung with a schraeder valve, I would have a 4-way adjustable shock. That pressure is additional adjustment you can do on the swinger 4way for example, so all the marketing on how nitrogen charged shocks are better is just guff.

I'm off to see how hot I gan get the oil on one of my favorite descents...

Luke

[shovelon]

Luke,

NIce work.

The nitrogen was used as a better gas to prevent heat buildup as it is compressed, but air should work.

[Luke]

After all, Air's 80% Nitrogen anyway.
And the oxygen obeys exactly the same gas laws as Nitrogen

As I say, sales guff; otherwise the multi-adjust shock manufacturers wouldn't have put user accessible valves on the pressure can.

An update: 5W shock oil is too thin for 30°c ambient temperature, but ok under 10°C

Looks like I'll be doing another oil change soon, I've found some 15W oil; we'll see if that's better.

Having done an oil change, I'm beginning to think that all this mystique around shock fettling is also sales patter...

[Matno]

Having done an oil change, I'm beginning to think that all this mystique around shock fettling is also sales patter...

Most things are... Now, if I could just figure out a way to cheaply replace the bushings in the lowers of my Manitou forks! (There are some things you probably can't get quite right without some fancier machinery than I have in the basement...)

[Old Proflexer]

I've never taken one of mine apart (but wouldn't be object to doing so).  I've one that has leaked -

If anyone has any pics of the process - please post and let me know  

OP

[Luke]

Hi
If it finally decides to get hot in my area I'll be changing my oil for thicker stuff. I'll put some pics up then.

Been having crappy weather in the Alps lately; might have to wait till August though
Luke

[keith]

Just had a bash at this myself,all going well untill I tried to pressurise the air chamber.Couldn't get any pressure in the shock with the needle inserted.I tried it down between the rubber bung and the metal top,if I push the needle straight through the rubber bung would the bung seal itself after withdrawing the needle.Any input welcomed.Also does anyone know how hard it would be to fit a schraeder valve to thetop of the shock?

[Luke]

I simply jammed the needle through the rubber bung!
When I pulled it out the bung closed up fine, even though this must have been the second time it was pierced.
I might be doing it again soon, the teflon tape bodge I did to replace a damaged O-ring is gently seeping.
4 months and counting, it's not seeping too fast, so I'll probably do the same again.
What's more with winter coming (salty roads etc.) a bit of oil covering the outside isn't a bad thing.
Luke's patented self oiling shock bodge...?
Nah!

[Thunderchild]

Nice job Luke.  Zen and the Art of Mountain Bike Maintenance!!!  If anyone on this list has not read, "Zen and the art of Motorcylce Maintenance" go read it!  

As for Oxygen in the shock.  Oxygen will oxidize oil whereas Nitrogen will not.  This could be one reason for no oxygen in the mix.  It might not make a difference in oil performance???

Notice:  Moving to tangent thought...
Anyone use or store linseed oil?  Serious fire hazard due to oxidation from exposure to air.  Natural oils oxidize more aggressively then petroleum/blended oils, but they too will oxidize.  I will try and post a picture of a CO2 cylinder that ruptured in a fire caused by oily rags stored improperly.  If I can remember how to post it that is.  It is impressive.

Thunderchild

[keith]

Surely if everything is sealed properly the air and oil won't come together.

[Luke]

There's a floating piston in the air can between oil and air, and the oil has no air bubbles in it; so it can't be too bad.
Like I said earlier, the gas (air/nitrogen) pressure is one of the user adjustables on the 4 way shocks, so there's a general acceptance of sticking air into the oil pressurising can.

But you're right Thunderchild, oxygen is more aggressive than nitrogen, not to mention the humidity you might pump into the pressure can.

IMHO the anodizing takes care of the corrosiveness and an annual oil change is pretty much essential anyway, so the oil's not going to have time to get dangerous.

...

Maybe that's why my shock once went BANG (really quite loudly) on the smallest of bumps, about 10 mins after I'd finished a killer DH (I live in the Alps and often used to boil the brake fliud in my 160mm Hopes) It had been a long time without servicing...

I've been meaning to read Zen for about 15 years already; maybe one day.

[keith]

Sorted mine now,thanks to Luke,great thread mate,as you said a valve in the top of the air chamber would be a good solution.Was thinking of using a presta valve off an inner tube with a bit of tube still attatched,pushed through the inverted top of the chamber.The presta valve is threaded all the way down its length making it easy to bolt on,the bit of inner tube left on the bottom when bolted tight would hopefully afford a seal.Using a presta to shrader adapter I could connect to my shock pump and pressure to suit.