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Old 09-03-2013, 03:20 PM   #1
motobene OP
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Inside the Ohlins GG45 Shock

Since I'm asking about info regarding the Reiger shocks, I thought I'd give as well as get

I bought an early model GG4510 shock when I bought my Econo. I rode it a couple of months then the shock went pfft! on me. What happened? I'll explain later....

Here is my Ohlins shock with the parts and stuff I bought from Ohlins:




According to Ohlins engineers, the internal volume is small, pushing the shock design. An odd failure can occur where the nitrogen reservoir piston can both fully extend toward the piston/valve stack and nitrogen gas can somehow get around the piston to charge the shock partially on the oil side of the piston. That make it impossible to disassemble even if you de gas the nitrogen reservoir, as gas is still in the oil side and you can't compress the seal head to remove the clip and disassemble the shock.

Ohlins said the shock wasn't re buildable, that some special Swedish machine was required, and they even put this note on the spec sheet:



...and that I should buy another $hock at, what, $750 or $o? I said, "no way, and would you please give me some tech info?" The conversation with the engineer apparent gave him confidence that I knew what I was doing, so I ended up ordering a new seal head and their latest recommended shock fluid, and getting some tech specs.

I decided to simplify my shock from #2 style in the following photo, to #1 style:



That is, from a DeCarbon separating piston design to the simpler so-called gas-emulsion system. Gas emulsion is a bit of a misnomer, as the gas doesn't really mix all in with the oil. Rather, the gas bubble just sits in the top of the shock and does was gas does... holds the shock together and seals the shock from the outside world. I can feel any difference between the two types.

Armed with a new seal head and simplifying the format, I was able to rebuild the shock to make it work very well. No problems at all in the ensuing many competitions. But first, I had to get it apart! I had to drill the old seal head to de gas the shock:



Another view (after disassembly) and you can see the small drill bit I used:



Now here is the separating piston, in the shock and a view of it removed:



Here is a view of the valve stack disassembled. Note the R for rebound and C for compression:



By the way, the ONLY the only valving difference I found between my early model GG4510 and later model GG4512 shock was the compression stack on the later version adds one more shim. That's it. Interesting, eh?



Oh and how did I get around the fancy needle-style gas filler valve thingie? I just machined my own Schrader valve from a stubbie version to press in to the body with cylindrical bonding agent. I just left the original valve in the shock:



On reassembly, I guess at the size of the nitrogen bubble at tip of shock, making it about what the original separating piston would have had. I charged the shock several times to go from 78% nitrogen (air) to somewhere in the upper 90s%. My shock pressure was somewhere between 80 and 120 psi.

The end result was a great working shock. I can't tell the difference between how it works as a type 2 versus the present type 1. It's just as quiet when it strokes.

motobene screwed with this post 09-05-2013 at 05:59 AM
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Old 09-03-2013, 07:53 PM   #2
lineaway
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So Chris, After the fact could you not just remove the shock body and just replace the seal? Great thread!
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Old 09-04-2013, 05:05 AM   #3
laser17
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Wow - Ohlins has there shit together with those assembly sheets. They even have a Sticker fitting code.
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Old 09-05-2013, 01:13 AM   #4
Twin-shocker
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Quote:
Originally Posted by motobene View Post
Since I'm asking about info regarding the Reiger shocks, I thought I'd give as well as get

I bought an early model GG4510 shock when I bought my Econo. I rode it a couple of months then the shock went pfft! on me. What happened? I'll explain later....

Here is my Ohlins shock with the parts and stuff I bought from Ohlins:




According to Ohlins engineers, the internal volume is small, pushing the shock design. An odd failure can occur where the nitrogen reservoir piston can both fully extend toward the piston/valve stack and nitrogen gas can somehow get around the piston to charge the shock partially on the oil side of the piston. That make it impossible to disassemble even if you de gas the nitrogen reservoir, as gas is still in the oil side and you can't compress the seal head to remove the clip and disassemble the shock.

Ohlins said the shock wasn't re buildable, that some special Swedish machine was required, and they even put this note on the spec sheet:



...and that I should buy another $hock at, what, $750 or $o? I said, "no way, and would you please give me some tech info?" The conversation with the engineer apparent gave him confidence that I knew what I was doing, so I ended up ordering a new seal head and their latest recommended shock fluid, and getting some tech specs.

I decided to simplify my shock from #2 style in the following photo, to #1 style:



That is, from a DeCarbon separating piston design to the simpler so-called gas-emulsion system. Gas emulsion is a bit of a misnomer, as the gas doesn't really mix all in with the oil. Rather, the gas bubble just sits in the top of the shock and does was gas does... holds the shock together and seals the shock from the outside world. I can feel any difference between the two types.

Armed with a new seal head and simplifying the format, I was able to rebuild the shock to make it work very well. No problems at all in the ensuing many competitions. But first, I had to get it apart! I had to drill the old seal head to de gas the shock:



Another view (after disassembly) and you can see the small drill bit I used:



Now here is the separating piston, in the shock and a view of it removed:



Here is a view of the valve stack disassembled. Note the R for rebound and C for compression:



By the way, the ONLY the only valving difference I found between my early model GG4510 and later model GG4512 shock was the compression stack on the later version adds one more shim. That's it. Interesting, eh?



Oh and how did I get around the fancy needle-style gas filler valve thingie? I just machined my own Schrader valve from a stubbie version to press in to the body with cylindrical bonding agent. I just left the original valve in the shock:



On reassembly, I guess at the size of the nitrogen bubble at tip of shock, making it about what the original separating piston would have had. I charged the shock several times to go from 78% nitrogen (air) to somewhere in the upper 90s%. My shock pressure was somewhere between 80 and 120 psi.

That's all the detail I have time for at present.....

Looks very interesting. I wonder was there any need to modify the piston, after converting it to emulsion type, and how did it perform after the alterations?
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Old 09-05-2013, 05:56 AM   #5
motobene OP
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Quote:
Originally Posted by Twin-shocker View Post
Looks very interesting. I wonder was there any need to modify the piston, after converting it to emulsion type, and how did it perform after the alterations?
No and it worked great. I went back and added a conclusion. Thanks for catching that.

And is there some account setting such that when you quote, you don't duplicate ALL the original text with ALL the photos? When I reply with quote it doesn't so that... at least on my end.
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Old 09-05-2013, 08:14 AM   #6
lineaway
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I probably should replace the seal on my son`s Raga this winter. It`s still working well. Though every so often there is suspect seepage. Seems all info from Ohlins has to do with in-house part numbers. To you ever figure out the seal size on the head?
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Old 09-05-2013, 09:09 AM   #7
Twin-shocker
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Quote:
Originally Posted by Twin-shocker View Post
Looks very interesting. I wonder was there any need to modify the piston, after converting it to emulsion type, and how did it perform after the alterations?
Good that it worked well..............I get the feeling that there is only a real need for separator piston, on trials shocks which are run body down ?

Lowering the volume of oil to fit the piston doesnt seem a good idea to me, and wonder how many other body up trials shocks have separator pistons fitted?
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Old 09-06-2013, 07:07 AM   #8
motobene OP
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Quote:
Originally Posted by Twin-shocker View Post
Good that it worked well..............I get the feeling that there is only a real need for separator piston, on trials shocks which are run body down ?

Lowering the volume of oil to fit the piston doesnt seem a good idea to me, and wonder how many other body up trials shocks have separator pistons fitted?
No production shocks these days are gas emulsion or type 1. They all have separating pistons. It's just the way things are.

The low oil volume cause some percentage of the GG45 shocks to fail under hard use. I imagine there are a few out there sitting on shelves. I can rebuild them, with or without separating pistons. But being marginal on oil volume doesn't guarantee they will fail. I tossed my separator piston because I wanted the simplicity of gas emulsion. Very easy to work on.
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Old 06-20-2015, 07:26 AM   #9
lineaway
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Before I forget the sizes, I figured I would post from just rebuilding the shock off my sons Raga. I bought a Motion Pro needle valve off Amazon for 18 bucks. It took me only 20 minutes to tear down the shock as the Ohlins is well built and made to service. As long as the seal head is not worn, the repair is very cheap. You can get the seal from your local hydraulic shop. The rod is 14mm. I used a 113 Quad seal (13.92mm) and a 14x22x3 wiper. Also replaced the body o ring 217. All under ten dollars.
Not listening to Bene`s great advice, I ended up doing it twice. I ended up tossing the piston separating as Chris suggested. Oil 65mm from the top and 200 lbs of nitrogen. All very simple! Then again I have worked in a hydraulic shop.
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Old 06-20-2015, 07:35 AM   #10
motobene OP
Motoing for 44 years
 
Joined: Mar 2013
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Quote:
Originally Posted by lineaway View Post
Before I forget the sizes, I figured I would post from just rebuilding the shock off my sons Raga. I bought a Motion Pro needle valve off Amazon for 18 bucks. It took me only 20 minutes to tear down the shock as the Ohlins is well built and made to service. As long as the seal head is not worn, the repair is very cheap. You can get the seal from your local hydraulic shop. The rod is 14mm. I used a 113 Quad seal (13.92mm) and a 14x22x3 wiper. Also replaced the body o ring 217. All under ten dollars.
Not listening to Bene`s great advice, I ended up doing it twice. I ended up tossing the piston separating as Chris suggested. Oil 65mm from the top and 200 lbs of nitrogen. All very simple! Then again I have worked in a hydraulic shop.
Thanks for the tech details on the needle valve and seals.

I assume it worked great?

When I sold the Econo with this shock, recently, I went ahead and changed the oil, just to be sure. I was shocked to find the oil after all that riding as a gas-emulsion shock was very clean. We rode for hours after the oil change. The shock worked well as usual. I sure like working on shocks that are meant to be worked on! And nothing is simpler than gas-emulsion. There is no bleeding. Assemble, gas up, purge gas (repeat a few times), Gas up to 225psi, then ride.
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Old 06-20-2015, 12:51 PM   #11
lineaway
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http://www.motionpro.com/motorcycle/partno/08-0075/
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Old 06-21-2015, 07:32 AM   #12
motobene OP
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I was asking about how the shock performed... if anyone, you, or your son, could tell any performance the difference between DeCarbon style and gas emulsion.

Thanks for the link for the needle!

Randy Lewis called me yesterday to say I didn't have to drill out the seal head to get it out, but there is a tool that can compress the seal head in. I said the gas had got around the gas piston and it had worked its way back all the way to bottoming in the bore, and I didn't have the tool. I also had a brand new seal head with seals already installed. He also said to hang onto the piston I removed, because it can be used in some other shocks, like some Betas.
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Old 06-21-2015, 09:34 AM   #13
lineaway
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Yeah, I just used the needle to release what I could. The shock came apart easily after that. My son said it was ok at Sipapu, but we had no time to mess with the settings. Hopefully this next week we can, since his summer basketball will be about over!
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