PerthMTB probably already figured out how to change the damper oil but I figured I’d post here to help anyone else searching for this.
The below is just my best guess, I’m no expert, but it worked just fine for me.
To service the CTD O/C damper:
-Remove the foot nut part way, use it to knock the rebound shaft loose of the lowers.
remove the footnut
-Use a 28mm (assuming a fox 34) 6 sided socket wrench filed/milled down to remove the chamfer so it has good contact with the nut flats to remove the damper cartridge from the crown.
-The damper cartridge including rebound assembly should pull straight up out of the crown.
-Put the cartridge in a 1″ shaft clamp (or use a strap wrench, or whatever you can come up with (don’t damage the cartridge by holding it too tightly)) to unscrew the compression damper out of the cartridge. It’s probably best to clamp about 1.5-2″ below the top of the damper so you don’t put extra pressure on the threads you are trying to unscrew.
-When the damper is unthreaded you can then pull the damper out, it has 2 o-rings that seal against the cartridge and can be a bit tough to pull out, go slow, be gentle, etc.
-Now your cartridge is open, dump the oil, cycle the rebound shaft a few times to get any extra oil out and replace.
-Put it back together the opposite way it was pulled apart.
I switched from Fox Red to Belray 15wt with 53 cSt @ 40c vs the fox which I believe is 47.30 cSt @ 40c. It a reasonable difference on the compression side. Descent mode seems more ridable and less wallowy now, its a small difference, not massive on a 2013 damper. However the rebound has slowed down enough with this change that I find myself running the rebound full fast, vs about 4 clicks out from full fast with the fox oil. I run my air spring pressure pretty low for my body weight, with more pressure I’m sure I’d be able to back the rebound off a few clicks from full fast.
Hopefully the above will help someone search for a how to get into the CTD O/C damper. 1″ Shaft clamps are the answer.
