Shock gas options

S

swazi_matt

Active member
There are no suspension guys anywhere near me and my shock needs a service (100+ hours since the last one so guess it is due!)

Anyway I watched it being serviced last time and think I might give it a go, the only hurdle is gassing the shock afterwards
How do you DIY guys do it?
I know some tyre shops offer nitrogen filling, but not sure if they can gas to the required pressure (+- 10 bar I think)

Anywhere else I can consider?
 
Tyre shops won't reach the pressures you need Matt.

Get yourself a lossless chuck and find a fridgey. Dry nitrogen is dry nitrogen. The other option is to simply use air (if you have a compressor that will run up to 10bar), or a shockpump (hand operated).
 
"dry air" can be used in a pinch if nitrogen is not available. I bought a nitrogen tank, regulator and a motion pro shock guage/filler - haven't used them in many years. I have Les at LT-Racing do everything for me now...

For DIY - you will need a shock filler/guage (or something similar) along with a needle kit - you need the optional needle for sachs/ohlins.

motion pro parts for nitrogen filling :

http://www.motionpro.com/motorcycle/partno/08-0075

http://www.motionpro.com/motorcycle/partno/08-0072/

You could probably homebrew something together using a "plunger chuck", a gauge and a needle...

jeff
 
The gauge is a good thing to have, however if your regulator is accurate it shouldn't neccessarily require a 2nd in line gauge. All the Sachs units I've seen use a schrader valve, but the Ohlins and Reigers do require the hyperdermic needle setup.

The other option you have is to contact some dealers (ktm/yamaha/etc) and see if any of them are equipped to regas a shock. Then you simply need to bleed it up yourself and pay them a small fee for the final N2 charge.
 
Do yourself a favor and avoid using air. oxygen and oil under pressure = boom
You could buy all the needed tooling for about the same price as a shock service.
Any real dealer should have the equipment to charge the shock for a small fee.
Since I do it all the time, a heavy equipment dealer would have everything except the adapter to fit the shock.
 
I wouldn't consider 145psi high pressure, and air only contains 21% oxygen. While oil and oxygen at certain pressures can go boom, in this scenario very unlikely.

Don't forget, downhill mountain bikes have suspension setups that make our dirt bikes look like toys, and its not uncommon for them to use air in the reservoir at pressures between 125-200psi, and they also recommend using the pressure as a tuning variable.
 
Thanks. We have fridge and fire extinguisher places here ... real bike dealers ... don't get me started on that!

Air might be a good option for now. I think I need a revalve but with it being so long since the last service whatever testing I do now is not really going to give accurate results. So maybe a service and air gas now, and then maybe take it across the border to South Africa for a nitrogen gas when I know everything is fine

What is the advantage of the no loss chuck? The manual says 150psi +- 25psi so if I use my bike pump that I use for my tubliss and get it close surely a bit here or there will not make a huge difference?
 
You don't need the no loss chuck, but you won't really be able to accurately gauge how much you've put in there. At the pressure and the volume of the ressie the small amount thats lost when uncoupling can be significant, as can the amount lost back into a gauge if you later try to measure it.

You can probably find one at a local store, however if not they can be found on ebay. The other option is to get a shock pump (http://www.chainreactioncycles.com/au/en/topeak-pocket-shock-dxg-pump/rp-prod7355)
 
I use similar to what Jake linked to above, a MTB shock pump, comes with gauge and lossless chuck already.

And I used air in the Sachs shock for over 100 hrs and several re-valves, also had air in the Reiger for almost 30hrs now. The Reiger was running N2 after the tuner re-valved it but I opened it for a service and simply changed the oil then re-gassed. With air! :eek:

I'm no gun rider but I have a reasonable ability to pick if something is wrong/difference with my bike. No perceptible difference between air and nitrogen that I can tell. I also haven't exploded yet so that's a plus :roll eyes:

My tuner is only 25 mins away and will re-gas for $7, but I don't bother, so take that for what its worth.
 
Ok i am going to give this a bash! have printed out the sachs shock manual (although will not be as thorough as i am just going for a service not a full rebuild)

2 questions

what weight oil? (and how much)
what was the trick to getting the shock out without stripping the bike down? seem to remember being able to drop it down, twisting and pulling it out sideways

ok that was 3 questions
 
Great find hamilton.

Removing the shock I've always found it easier to just remove the lower subframe bolts and swing the back end up. I tried the drop and twist but in the end it was more work for me.. more frustration anyway!

Viscosity of oil around 15cSt at 40C, with a high VI rating (wouldn't consider anything under 200). That viscosity could put you in a 2.5wt/5wt depending on brand.
 
That is the document i have, but i think it is a bit overkill for a simple service and possible revalve

@jakobi where do you see the VI rating of oil? I have about 800ml of belray 2.5 that i am hoping will suffice.
 
ok just done some googling and see that the bel-ray 2.5 fork oil has a vi of 60
the best i can get locally is silkolene 05 synth fork oil which is about VI220

I suspect i will be redoing this in the near future so may just use that with air until i have my valving correct and then replace with shock oil and N2 gas
 
hamilton said:
Found this on the beta site, nice detailed A&D manual.
Might be a help to you.

http://www.betausa.com/sites/default/files/pdf/Sachs.shock.manual-HR.pdf
Click to expand...
Has anyone tried the beta shim stack suggested at teh back of this document?

I am not sure what was OEM GG, but this is the comparison between the document and what i have with my racetech gold valve:
Beta ***** ***** Racetech
2 24 2.00 ***** 1 24 0.30
3 22 0.30 ***** 1 26 0.30
1 24 0.25 ***** 1 28 0.30
1 26 0.25 ***** 1 30 0.25
1 28 0.25 ***** 1 32 0.25
1 30 0.25 ***** 1 34 0.25
2 32 0.25 ***** 1 36 0.25
1 34 0.30 ***** 1 38 0.25
1 36 0.30 ***** 1 40 0.25
1 28 0.10 ***** 1 30 0.10
4 38 0.20 ***** 2 40 0.20
valve valve valve *****
3 44 0.20 ***** 6 44 0.20
3 44 0.15 ***** 1 32 0.15
2 40 0.15 ***** 1 44 0.25
1 28 0.15 ***** 1 42 0.25
1 44 0.15 ***** 1 40 0.25
1 42 0.15 ***** 1 38 0.25
1 40 0.15 ***** 1 36 0.25
2 38 0.15 ***** 1 34 0.25
1 36 0.20 ***** 1 32 0.25
1 34 0.20 ***** 1 30 0.25
1 32 0.20 ***** 1 28 0.25
1 30 0.25 ***** 1 26 0.25
1 28 0.25 ***** 1 24 0.25
1 26 0.25 ***** 1 22 0.25
1 24 0.30 ***** 1 20 0.25
1 23 0.30 *****
1 24 2.00 *****
 
I wouldn't worry so much about the air and oil causing an explosion ... if you've done it right they never meet :cool:

The compressed air is on one side of the sliding piston and the oil is on the other. Nitrogen is adventageous in that it is more temperature stable, and due to larger molecule size less likely to leak past seals.
 
ok i have started

took a bit longer to get the shock out than i remember, but there is a possibility that the last time i did it i was busy sorting other parts out already.

did it late last night so got as fat as loosening the spring, now - the spring is just about the same length as the free space on the shock so what are the tricks to compressing the spring so i can remove the lower collar?

PS with the shock last being serviced in about july 2012 it was nice to discover that it still has over 150 Psi in the reservoir. But i am guessing that the oil is well past its use by date

and on the tpic of oil, the suspension fluid that i was told was available was incorrect, it was actually the silkolene pro rsf5 which has a vi of 378 so score there. close match with the sachs spec.
 
RSF 5wt is probably a bit heavier than I'd prefer (2.5wt would be better) but it will get the job done and hold up well.

Removing the spring you'll need to rig something up to compress the spring slightly. If its just a few mms a bit of body weight applied carefully in the right places can make it happen (with someone else pulling the retainer). Otherwise you'll have to get creative. I have some little threaded rod ones that clip over a coil each side and you crank down on them. Real pain in the bum to use, and also mark up the spring if you have to get heavy on it.

Regarding disassembly, if you just want to change the oil you don't have to do much.

Turn all the clickers wide open (especially rebound, to seat the needle)
Let the N2 out of the ressie, and remove the valve stem.
Remove the cap from the bottom of the shock body to expose the seal head.
Push seal head down into the shock.
Remove the circlip (have fun!)
Pull the shaft, seal head, and piston up from the shock (watch for when it lets go).
Push the res cap into the body, remove the circlip, and pull the cap out.
Remove the separator piston.

From there drain and clean up with compressed air.
Make any adjustments to valve stacks.

Reassembly follow the manual.
Fill N2 ressie to top (with oil).
Drop separator piston in and be sure some oil overflows (no air).
Bottom it out - This forces oil past the comp adj. I actually like to insert the cap and circlip and use air pressure to hold it bottomed.
Add some more oil to the body.
Bleed the main piston up (slow strokes).
Top up and draw the rod up also (don't come high enough to let air in).
Bring the seal head down and let more oil overflow as it seats against the o-ring.
At this stage if you have put some air into the ressie, you'll need to press the valve down and let air out as you push down on the seal head. It will allow the seal head to drop in and displace the oil over to the ressie side.
Insert circlip and pulll assembly back out to bottom the seal head.
Remove valve stem and ressie cap again, double check measurement down to piston.
All good - put everything back together and gas it up to 10bar.
 
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