Outcast Outcast Squat - Good or bad?

[Buck]

So then it is not possible to adjust rebound in RC shocks?
That is quite the statement...I think a fair amount of folks in this hobby would disagree, and likely many of whom are far more qualified than me.
To each their own at the end of the day, but the forum is a place to discuss matters freely, and share experiences within all facets of the hobby. Calling another's statements or ideas 'idiotic' is not necessary. Offering constructive feedback and/or correction when warranted is always welcome...and having a little tact along with it - goes a long way!

 

[ShaneF]

Where you place the piston within the shock while tightening the cap is exactly how you set rebound.

 

[jonUF02]

I'm so confused on this thread. I have always thought that the goal was to leave no air in the shock body, except between the bladder and cap??? I can't see how the piston position at the time of tightening has anything to do with where it travels. There are holes in the piston, the fluid flows through them at a certain rate depending on the fluid thickness and size of the holes. The shaft should move all the way in and out freely at that rate, and the spring controls the rate of rebound. It seems that Arrma instructions tell you to move the piston up a bit before tightening to avoid excess fluid pressure depressing the bladder as the threads are tightened, or avoid air pockets below the piston.

The Nero caps have a bleed screw in them that allows to tighten the cap, then insert the screw when complete, like the diffs on the Kraton.

 

[robl45]

Exactly. The only way that setting the piston at a certain place could do anything is if you are leaving air in the shocks. I looked at the manual the other night and it explains the typical bleed procedure which would allow you to remove air from the shocks.

I'm so confused on this thread. I have always thought that the goal was to leave no air in the shock body, except between the bladder and cap??? I can't see how the piston position at the time of tightening has anything to do with where it travels. There are holes in the piston, the fluid flows through them at a certain rate depending on the fluid thickness and size of the holes. The shaft should move all the way in and out freely at that rate, and the spring controls the rate of rebound. It seems that Arrma instructions tell you to move the piston up a bit before tightening to avoid excess fluid pressure depressing the bladder as the threads are tightened, or avoid air pockets below the piston.

The Nero caps have a bleed screw in them that allows to tighten the cap, then insert the screw when complete, like the diffs on the Kraton.

 

[Buck]

The amount of oil in the shock affects the level of pressure built up in the shock body under compression and determines how quickly the piston will push away under force. Said force is a combination of the volume of oil and residual air (of which there is only a little behind the bladder).
When you push the piston up after partially tightening the cap, some additional oil escapes because you are moving oil up and out through the bleeder more quickly than it can escape back down through the holes in the piston.
The excess oil removed, lightens the amount of pressure the piston is under when the shock is fully compressed and therefore determines how much force, and ultimately the degree of rebound the shock will have.

 

[robl45]

Its oil in the shocks, not nitrogen gas. There is no pressure.

The amount of oil in the shock affects the level of pressure built up in the shock body under compression and determines how quickly the piston will push away under force. Said force is a combination of the volume of oil and residual air (of which there is only a little behind the bladder).
When you push the piston up after partially tightening the cap, some additional oil escapes because you are moving oil up and out through the bleeder more quickly than it can escape back down through the holes in the piston.
The excess oil removed, lightens the amount of pressure the piston is under when the shock is fully compressed and therefore determines how much force, and ultimately the degree of rebound the shock will have.

 

[Buck]

Yes there is pressure.
When the piston is compressed to the top of the shock body, the oil between it and the bladder does 2 things: it escapes down through the holes, and it pushes on the surface of the piston around the holes.
Think about the dynamics of it...shock compresses quickly...and where does all the oil above the piston go? It can only go down through the holes so quickly....the rest of kinetic energy built up in essence drives the piston down away from the top of the shock and the bladder = rebound.
Shock motion creates kinetic energy, this energy in concert with the oil and the piston is what drives the forces that create damping and rebound.

 

[Magnus_CA]

...It seems that Arrma instructions tell you to move the piston up a bit before tightening to avoid excess fluid pressure depressing the bladder as the threads are tightened, or avoid air pockets below the piston.

Just a clarification...The manual wants us to retract the piston fully before closing the cap.

 

[Buck]

Retract for initial turn and bleed - save for 2mm of threading, then fully depress piston and completely tighten. If you look at the right-most pic in image 4, the shock is fully depressed before final tightening is performed.
I tried their recommendation and ended up with virtually zero rebound.

Just a clarification...The manual wants us to retract the piston fully before tightening the cap.

 

[robl45]

Yes, that's the right way to do it. That's how you get the air out of the shock.

Retract for initial turn and bleed - save for 2mm of threading, then fully depress piston and completely tighten. If you look at the right-most pic in image 4, the shock is fully depressed before final tightening is performed.
I tried their recommendation and ended up with virtually zero rebound.

 

[Buck]

Yes it's not wrong, but is inherently limiting as far as rebound.
We can agree to disagree on this topic, it's all good man...just saying - there are countless threads on line and videos of how to set rebound.
The instruction manual shows the method for very little rebound.
To gain maximum rebound - the piston is only slightly depressed.
Not sure why the air issue is a recurring theme here. When you fill the shock completely, and turn the cap initially and oil comes out of the bleeder holes, that is removing any excess oil and air.
Piston placement thereafter before fully tightening - affects rebound.

 

[Magnus_CA]

I think I'm going to give low rebound a shot next time. I think it would be easier to get consistent behavior when the goal is zero to low rebound and it makes sense to me that zero rebound equals maximum damping. Your spring is then your source of rebound, which removes the variations in performance due to excess oil or air in the cylinder. Sounds good on paper but I'll have to see if it makes a difference with squat.

 

[Buck]

All boils down to preference.
You absolutely should try it both ways!
It's a trade off in the end...more stability over bumpy terrain, or more agility on harder flatter surfaces.
Depends entirely on your environment.
As far as squat you will absolutely get more of it with less rebound as the force pushing against transitional weight distribution will be less, but that is not a bad thing.
All depends on what you like

 

[ShaneF]

. This video is a little dated,but explains pretty well. I believe gord tessman has a good video explaining how to set rebound as well.

 

[Buck]

Thanks Shane.
That is actually one of the ones I watched before doing my shocks.
Explains the concept perfectly, and removes any doubt I think, relating to the facts I outlined above.

. This video is a little dated,but explains pretty well. I believe gord tessman has a good video explaining how to set rebound as well.

 

[Magnus_CA]

It just goes to show how varied the opinions are with regards to shock rebound. That Losi video was made 6+ years ago and then just a year ago the same pro made another video where he tuned for virtually no rebound:

Here's another 4 videos from 4 different pros all shooting for zero rebound:

Here's another pro that advocates about 25% rebound:

 

[ShaneF]

Its a preference for sure. Was only trying to say its not "idiotic"

 

[slpcrf450x]

Exactly. The only way that setting the piston at a certain place could do anything is if you are leaving air in the shocks. I looked at the manual the other night and it explains the typical bleed procedure which would allow you to remove air from the shocks.

I think you might be a little confused. They are not suggesting that you leave air below the bladder. The only air is above the bladder where it can't mix in with the oil. By doing it this way you are simply using the volume of the shaft as it enters the shock to compress the air that is between the bladder and the cap, creating a little pressure that allows the shaft to "rebound" back out.

 

[ShaneF]

Thats right. If there was air being left within the shock body itself, then there would be no excessive oil leaking out while tightening the cap. I have never built a shock and not had oil leak while tightening the cap.