How much shock oil to fill up and how much bounce back is ideal?

[babolimp]

I've watched a few videos on how to fill shocks and unfortunately the information doesn't really seem consistent when it comes to the most important part. So I come to you guys, the information bank, with my two questions.

1- When filling shocks on the final fill up just prior to putting on the cap, how far up/down should the piston be? I have seen videos ranging from all the way down to all the way up.
2- Once the shock is all closed up, how much bounce back are you aiming for when you compress the piston? Again, I have seen a range of levels of bounce.

FYI I have an outcast 6s if that's relevant.

 

[Greengaunja]

When full and bleed, a fully compressed piston should extend at least halfway out on its own when let go(without spring attached)

 

[SrC]

I like neutral shocks. No rebound at all. Hard to achieve. Easier to dial this in with emulsion shocks IMHO. Thats another topic. But your shocks have diaphrams, I would close the cap Slowly about half the way first while slowly pushing the piston all the way up, to let out excess oil holding the top at an angle. Once piston is all the way in the oil and some air bubbles release and stop, quickly tighten. Pump the shock a few strokes and see how far it pushes out. a few mm is close enough. the trick is to make pairs of shocks ( Fr or Rr) exactly the same rebound wise. You should not hear any squishy sound while compressing. Comes with patience and practice.
Other may chime in withh their technique. Mine is basically from the manual. But I do other things like use a shock pump etc. But what is stated is the basic way of doing it with good results. I completely disassemble mine and use a shock lube like Green slime or Protek o ring lube. This is all optional if the shock has no issues and just changing out for different oil or cleaning out the dirty old oil.
Clean all well, removing all the old oil and check that the piston is fully tightened, but will still rotate on the shaft with slight pressure. Preparation before filling is important as well as letting the shocks sit open when filled for at least 20 minutes if not using a shock vacuum pump. Air in the oil is your enemy. The finest bubbles you cant see must rise and be gone.

 

[parcou]

^^^^ Like

I found so many videos it gets confusing.... @babolimp what RC are you working on.....

 

[babolimp]

interesting. even here a couple of different opinions on the bounce back. at least half way vs a few mm to no bounce.

@parcou outcast 6s 2018 model AR106032

 

[Greengaunja]

interesting. even here a couple of different opinions on the bounce back. at least half way vs a few mm to no bounce.

@parcou outcast 6s 2018 model AR106032

That's why like everything else, it comes down to driving style, surface, and just general preference. What works for one person might not for another and vice versa.

 

[SrC]

^^^ This ^^^
Honestly, rebound stroke/pressure is subjective. Remember that it is pressure from the compression stroke that determines how much the piston rebounds after the shock is filled and bled. I have experimented with differing amounts. It is my prefernce like stated above. Is there one correct way? NO. I just like mine as neutral as can be. Never seen any advantage with anything else. But if you have too much pressure and too much rebound results, it will cause shock issues. Blown seals at the bottom cartridge, for instance. Leaking shocks. More mainteneance required. Many track guys also like them neutral (dead). Just something I've done since my track days. Whatever your style, make sure they are matched well enough in pairs. F and R sets.
The "Spring" rebounding the pistion should be the only force bringing the shock back to full extension IMHO. In this way shock pack is more accurate from shock to shock. More predictable handling results. Just my spin.

 

[Greengaunja]

^^^ This ^^^
Honestly, rebound stroke/pressure is subjective. Remember that it is pressure from the compression stroke that determines how much the piston rebounds after the shock is filled and bled. I have experimented with differing amounts. It is my prefernce like stated above. Is there one correct way? NO. I just like mine as neutral as can be. Never seen any advantage with anything else. But if you have too much pressure and too much rebound results, it will cause shock issues. Blown seals at the bottom cartridge, for instance. Leaking shocks. More mainteneance required. Many track guys also like them neutral (dead). Just something I've done since my track days. Whatever your style, make sure they are matched well enough in pairs. F and R sets.
The "Spring" rebounding the pistion should be the only force bringing the shock back to full extension IMHO. In this way shock pack is more accurate from shock to shock. More predictable handling results. Just my spin.

Very true. For me, the springless rebound just shows I have pressure. Yet I can see how zero rebound ensures equal sets. If one rear rebounds halfway and the other a quarter of the way, you will have traction issues. I tend to overthink and treat my Sentons the same as I did with my RL offroad trucks. Struts and shocks have rebound so I expect it here. But yes, the spring should be more than sufficient for RC shocks to work properly simply due to less weight and pressure.

 

[SrC]

^^^ This.
I know what you are saying with scale shocks on real vehicles. But they are pressurized with nitrogen and mfr'ed pretty much all the same. Because of heat that scale shocks endure. A different animal.
With RC shocks , they are handbuilt and filled and its hard to get them matched. Many don't know any difference and its all good for them. There is no real right way. It is all subjective. Just absolutely avoid hydro-locking your shocks at any point in the stroke.. And this is why I tend to go the other direction and want a neutral or "dead" rebound. Sometimes atmospheric pressure and ambient temps affects internal shock pressure. I want the springs to do all that work. I just want "dampening" from the shock stroke, "not" rebound assistance with undue shock internal pressure to assist rebound in any way.

 

[Greengaunja]

^^^ This.
I know what you are saying with scale shocks on real vehicles. But they are pressurized with nitrogen and mfr'ed pretty much all the same. Because of heat that scale shocks endure. A different animal.
With RC shocks , they are handbuilt and filled and its hard to get them matched. Many don't know any difference and its all good for them. There is no real right way. It is all subjective. Just absolutely avoid hydro-locking your shocks at any point in the stroke.. And this is why I tend to go the other direction and want a neutral or "dead" rebound. Sometimes atmospheric pressure and ambient temps affects internal shock pressure. I want the springs to do all that work. I just want "dampening" from the shock stroke, "not" rebound assistance with undue shock internal pressure to assist rebound in any way.

The way you explain it makes it all make sense in setting up your way.