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6/30/2023
Location
Seattle, WA
US
So I'm a cheap bastard and have bought a used ohlins coil shock for the 2nd time.
Each time I've bought one used, I'm pretty sure the piggyback has had low pressure.
Why do I think this? I can feel a dead band in the shock, almost like a top out when I pick up the bike. It feels almost like the shock is loose but everything is tight.
3 questions:
- Am I correct that this is a result of a low pressurized bladder?
- Is there an easy way to pressurize it? I know it's supposed to be nitrogen but I've seen videos of people doing it with a shock pump and additional fittings.
- Finally, do these shocks generally need more service than a coil with an IFP? I like fiddling with and trying hardware but don't want to have to keep paying a lot to get this thing serviced/maintained of it's a pretty regular thing.
Any info and advice would be helpful!
Apologies if this doesn't help but I recall a local youtuber (MTB Telly) complaining about rebound top-out on a TTX 22 even after he'd corrected the bladder pressure, i.e. it might just be intrinsic to the design.
A lot of double barrel shocks suffer from topout because they usually cannot implement a hydraulic topout system like most monotube shocks have. So it's pretty important not to have to much spring preload, out you will have to slow down LSR
I may have described it incorrectly. It's not exactly top-out and I'm not using much preload but basically if you pick the bike up, it feels like there's a dead band in travel the shock almost feels loose.
Are you sure the looseness/knocking isnt in your linkage bolts or maybe you are pushing on your saddle, and feel your dropper moving?
If its really the damper, check by removing it and its coil, and feel it while moving it through its stroke clamped in a vice. If its still a deadband or knocking, something is not good, and you should have someone service it.
Realizing it might be that I'm not using enough preload or setting it before putting the shock on the bike.
Pretty common on TTX22m shock and can be worse on some bikes than others but in most cases they can have a very light top out knock.
The upgraded Factory M2 Damper Shaft fixed this - https://suspensionwerx.com/products/ohlins-ttx22-m2-factory-racing-upgr…
They are pressurized with a nitrogen needle and can only be done that way as there is a rubber puck that the needle needs to go through. Unsure if there are aftermarket mays around this.
TTX22 is bombproof and can likely well outlive most other offerings in terms of servicing, the steel shaft and robust seal layout means they go for years without hesitation.
It's common for twin tube shocks to have a top out knock - since the oil needs to flow back up to the reservoir it is tricky to have a traditional hydraulic top out circuit, which closes off the rebound free bleed a few mm before full extension.
It does appear that the updated shaft has added a top out system if thats possible for you
Otherwise if it feels "loose" it might simply be air in the oil, or the shock is leaking and the bladder is over extended. Not uncommon for a shock more than a couple of years old. Bladder shocks can have air permeation from the bladder in to the oil, but most modern shocks used thicker rubber or a design that minimises it to a point that it shouldnt get aerated much faster than an IFP shock
You can charge any shock like that with a cheap needle like this, if the needle is sharp the rubber plug can be reused a few times, or use a short piece of o-ring cord to replace it if it won't seal.
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