Shock spring rate vs fluid weight vs piston

[CTYankee]

I've been in and out of RC for years and am getting back into it now that my son is old enough. In the last 3 years I've gone down the rabbit hole of mountain bike suspension tuning. They can be very complex systems with orifice dampers, shim stacks, air springs, coil springs, bladders, Internal floating pistons...you name it. I understand suspension pretty well for a layman.

Now that I'm back into RC, I'm puzzled at how little suspension tuning carries over to these. Typically you start with your spring (air or coil). The goal is to get the right spring rate so the vehicle isn't too wallowy or too harsh. Then you move on to damping. Rebound first, then compression (Low speed and high speed).

RC shocks are pretty simple. They have a coil spring and a single orifice damper that is for rebound and compression (both low speed, no high speed circuit).

With crawlers I often see people adjust the fluid weight to compensate for stiff shocks or as they add/remove weight. That does sort of help, but ultimately it sounds like a spring rate issue.

I see times when people use lighter fluid when larger holes in the piston would probably help more. Why? Larger holes allow more flow (same effect as lighter fluid) but would remain sensitive over bigger hits that could otherwise choke the small hole. Orifice damping is very sensitive to shaft speed. At a certain point when the force/speed of the shaft gets too high, the hole is too small and the shock gets much stiffer. So if you want to keep the shocks active and plush, bigger holes in the piston would help more than lighter fluid.

Has anyone played with piston changes and fluid changes in combination?

Oh, and anyone ever compare fluid viscosity across different fluids? Viscosity is what matters and you'll find one 10WT is another's 15WT.

Anywho...Its probably just easier to throw in lighter fluid and call it a day. Or is there some other reason?

 

[Voodoobrew]

When you're crawling slow the fluid is kinda more for lubrication and less for dampening because the speeds are so low any fluid in the little holes gives you enough dampening.

This is just my opinion though. I use 30wt silicone oil, simply cause that's what the cashier grabbed first. Haven't had any issues.

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[Voodoobrew]

Well no issues that suggest tuning anything other than spring configurations would help.

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[Duuuuuuuude]

When you're crawling slow the fluid is kinda more for lubrication and less for dampening because the speeds are so low any fluid in the little holes gives you enough dampening.

This.


But yeah, a lot of suspension tech gets ignored. The margin of "good enough" is really wide on a crawler. :ror:

 

[WHITE-TRASH]

This.


But yeah, a lot of suspension tech gets ignored. The margin of "good enough" is really wide on a crawler. :ror:

For the masses, yes. Especially in scale. "I just run a couple drops of fluid to lube the shaft cuz it leaks out anyways. I win comps all the time so I know whut ima talking about!" Sure cletus, sure you do. :lol:


If you want to go down a different rabbit hole find a set of MIP bypass pistons.

 

[mass-hole]

I don’t see big hits being an issue for crawlers, but i get what youre saying. I am honestly a little surprised that RC shocks are not more “scale” in that sense when consider the technology available on 1:1 for anything from desert racing to crawling.

Hell my mountain bike suspension is 100x more advanced. adjustable air spring with independently adjustable high and low speed compression and rebound dampening.

 

[JDM74]

In my limited knowledge of shock tuning, I was able to fix the issue I had with my bomber. See link below, post 732.

http://www.rccrawler.com/forum/axial-rr10-bomber/556101-what-did-you-do-your-bomber-today-37.html

That change was done with just a fluid change. If it didn't fix it my next step was to open up the orifices on the front shocks and go a bit heavier on the fluids. I think my spring rates were just about right because I was sitting at about 50% sag, so I had equal travel up and down from the static position. This was all done with my typical battery in the rig. FYI this is faster rig and not a crawler. It does crawl just fine with the suspension set up the way it is.

 

[OSRC]

... a lot of suspension tech gets ignored. The margin of "good enough" is really wide on a crawler. :ror:

Very true. It's a much different game compared to "go fast" vehicles where shock tuning is much more important for a good handling vehicle.

Never bother with pistons really, usually I can get where I want to be with oil changes. I start with springs first to get the balance right front to rear, then go to oil to tune the roll rate. I'll use anywhere from 20-60wt depending on the rig. It's pretty obvious to me when I've got too light or too heavy dampening, but I'd wager most people don't mess with it much.