Are these shocks meant to have air in them?

[Tbird232ci]

This feels like a stupid question. I've build countless shocks from Tamiya, Yeah Racing, 3racing and Yokomo and I can get them to be silky smooth with no air in them. I'm working with some RC10CE shocks, top loaded with plastic caps. I replaced all of the O-rings and used a liberal coating of green slime. But, I can not get these to either not have too much rebound, or not have what feels like absurd amounts of air in them.

What am I doing wrong? Have I missed something obvious? I really appreciate any help.

[JosephS]

What do your shock caps look like?

The ones above were a running change by associated. They make it much easier to bleed the shocks.

[Tbird232ci]

Mine do not have the bleeder screws. They are just solid black.

Are those caps available for the old shocks?

[Tbird232ci]

I just did a quick Google search and found those shock caps.

You sir, are my hero.

[juicedcoupe]

While I like the bleeder caps, you can do it without them.

[jwscab]

Yes they are emulsion shocks and need air in them to function properly. It takes a little bit of practice to bleed without the bleeder screws.

[Tbird232ci]

Yes they are emulsion shocks and need air in them to function properly. It takes a little bit of practice to bleed without the bleeder screws.

This statement helped immensely. I've always built bladder shocks, and I didn't realize these were emulsion shocks. Knowing the name led me down some YouTube rabbit holes and now I have a much better understanding on these things.

I really appreciate all of the help.

[morrisey0]

I have never done the piston up technique, and TBH, just read about it now. With the piston down, I always fill to the top of the cylinder (after bleeding the piston a couple of times), and just at the top seems to be about right. Then put the cap on and try it out, and if too much (won't compress fully), open and sponge a little off with a paper towel. If not enough (compresses and doesn't rebound a little), open and add a drop or two.

[Dangeruss]

I have never done the piston up technique, and TBH, just read about it now. With the piston down, I always fill to the top of the cylinder (after bleeding the piston a couple of times), and just at the top seems to be about right. Then put the cap on and try it out, and if too much (won't compress fully), open and sponge a little off with a paper towel. If not enough (compresses and doesn't rebound a little), open and add a drop or two.

That's how I've always done it.

I prefer the piston at the bottom so the shock adds some extra compression damping to the suspension... Alternatively putting the piston in the center of the body while filling provides equal resistance to movement in both directions and putting the piston at the top will cause the shock to retract on its own. The purpose of gas charging automotive shocks (low or high pressure) is to combat this phenomenon by providing space for the oil displaced by the shock shaft during compression so it doesn't affect the spring rate of the suspension.

Interestingly, OGRC is making functional piggyback shocks with a spring-loaded piston inside the external reservoir that has a thumb screw on the bottom. As the shock compresses the oil displaced by the shock shaft compresses the spring in the external reservoir, making that spring act like a gas charge. The less preload on the spring the "lower the gas charge" and the softer the shock is. The more spring preload is adjusted in the "higher the gas charge" and the stiffer the shock becomes. Exceedingly cool tech, even if Bill Cambell, the President of Delta Manufacturing, pioneered it over 40 years ago.

Back in the day RC Sprint Cars used to run springless. Heavy shock oil and pistons with big holes so the shocks were softer than the oil weight would suggest, they relied on the excessive compression damping to support the car without springs. Trick stuff.