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Discussion Starter · #1 ·
Can anyone please explain the types of rear shock?

I bought a new shock for my bike off eBay, as it was going for only 99p. And I figured I will likely kill this one with the amount of two up riding I do....

The new one however, has that little gas bottle thing, which I assumed was just an oil expansion resevoir or something, but it says it contains gas? Which is fair enough, that would make sense too...

But the point is, my current shock doens't have one :S

What is the difference?
 

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As far as I know- the main advantage is travel.
With the reservoir out of the way they can make shocks which have a lot longer travel.
I imagine it also makes them easier to rebuild and such
 

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Discussion Starter · #3 ·
As far as I know- the main advantage is travel.
With the reservoir out of the way they can make shocks which have a lot longer travel.
I imagine it also makes them easier to rebuild and such
So this new one is the same, but with an EXTERNAL reservoir?

personally, I think it looks cool :p

The gas thing on it...
I am assuming that is just because it is filled with something (Nitrogenperhaps?) along with the oil.
Because.... air would get very hot under compression or something?
 

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I'd imagine that's the case!
Something similar to the reason Nissan used Nitrogen for their tyres.
It's just generally more stable.

I think we'd again have to wait for the word from our omnipotent lord of engineering though. I've never worked first hand with suspension systems!
 

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Some dampers are charged with gas, typically nitrogen. These shocks have an extra unattached piston in the bottom of the damper cylinder, with oil above the piston and high pressure gas below the piston. When you hit very large bumps at high speeds, causing very high damper piston speeds, the floating piston will move, reducing the damping and allowing the shock to respond faster. Also, on an emulsion shock, if the damper piston moves too fast it can pull so hard on the oil that bubbles form. This is called cavitation. These bubbles form in thousandths of a second, but can take hours to pop. As long as there are bubbles in the oil, your dampers are pulling through a mixture of oil and foam. This ruins your damping. The free floating piston will keep the oil pressure above the cavitation pressure. Typically, nitrogen at 30 to 300 psi is used because the oil won't combine (burn) with the nitrogen nearly as easily as it will with the oxygen in normal air.

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Discussion Starter · #8 ·
Current Shock:



New Shock:
 
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Discussion Starter · #9 ·
Oh, so I went to a mechanic today, because I am slightly worried about how low my rear end sags especially when two up :p

He said just take a c spanner and play around until it feels right.
This TOTALLY contradicts what they say all over the 'other forum I browse, no names mentioned'. (They aren't an overly friendly bunch there).

Is this a particularly good idea? :S
Or am I likely to massively screw it up ><
(no pun intended...)
 

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It's all about sag, have a look round for articles on it by Dave Moss, very clued up guy on suspension, went to a talk once by him, fascinating evening.

Spot on Scott, exactly how it works, another useful side effect is as there is a bigger amount of oil, the damping rate is less effected by heat, dampers will warm up when a bike is ridden hard, from absorbing the energy not from the exhaust and engine. Feel your fork legs after a good thrash. You can get the same thing happen with car dampers but you really have to be going for it, had it happen once, not nice experience.
 

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Discussion Starter · #11 ·
It's all about sag, have a look round for articles on it by Dave Moss, very clued up guy on suspension, went to a talk once by him, fascinating evening.

Spot on Scott, exactly how it works, another useful side effect is as there is a bigger amount of oil, the damping rate is less effected by heat, dampers will warm up when a bike is ridden hard, from absorbing the energy not from the exhaust and engine. Feel your fork legs after a good thrash. You can get the same thing happen with car dampers but you really have to be going for it, had it happen once, not nice experience.
Soo.... this new shock will be better in some way shape or form? :p
 

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Discussion Starter · #13 ·
Okay cool :)
 

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Discussion Starter · #14 ·
And as for adjusting my own suspension with a C spanner?
 

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It's all about sag, have a look round for articles on it by Dave Moss, very clued up guy on suspension, went to a talk once by him, fascinating evening.

Spot on Scott, exactly how it works, another useful side effect is as there is a bigger amount of oil, the damping rate is less effected by heat, dampers will warm up when a bike is ridden hard, from absorbing the energy not from the exhaust and engine. Feel your fork legs after a good thrash. You can get the same thing happen with car dampers but you really have to be going for it, had it happen once, not nice experience.
I'd like to make a note that i copied and pasted that for Cameron from something i found online i do not know that much about suspension.:D
 

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Discussion Starter · #17 ·
Measure then adjust, that way if you don't like it, you have a reference point to go back to. For preload, check the sag amounts, then adjust accordingly.
Fair enough :)
My main issue, is that my bike simply sags too much when I ride two up ><
 

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Fair enough :)
My main issue, is that my bike simply sags too much when I ride two up ><
If you measure how much the sag is one up and you are happy with that, then measure it two up, wind the preload till it matches the sag as one up, and that should in theory give you a base figure to start from. It will never handle as well two up as it does one up. Do yourself and her a favour and get her riding her own bike.
 
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