Understanding base and mid valve function

I recently did some of this research and messing around with my shim stack myself on my bike, This is what i found.

Removing shims from the mid valve makes the base valve have to work "harder" if you want to think of it that way. You can feel a rubbery kind of feel. I think this is because of the spring effect in the base valve. When you remove shims from the base valve the mid valve will have to do more of the work. The effect is a crisper feel. I believe they have to be valved to be "equal" in how much work they each do. It shouldn't be one or the other doing most of the work.  Thats all I know. 

If you were looking for valving advice, remove one face shim on each and give that a try if you want to go softer. 

https://youtube.com/playlist?list=PLHSgGy8X-DgWVWBw-yR10u0tFgi8qQAG8

Check this guy at YouTube out. Great content how suspension works. The link is his tech-playlist.

A lot more oil moves through the midvalve so it should be a bigger lever to change. If midvalve is too stiff and base too soft you can get cavitation.

Your springs need to be correct before any valving.  Also, you cant stiffen what you have without shims, so buy some and add 2 face shims to your base valve.  Start from there.

What forks and what bike is it? 

Stop by AEO//REP and try to bend an ear…

Mid valve is where the magic is.

I just did a set if those. Had to stiffen both the base and the mid before they worked well.

Do you know what the valving looks like right now? Are you able to post it?

Personally, I go a bit heavier on the springs and lighter with valving.  Guys bikes setup for 30# heavier than me seemed to work better.

You can make a fork work with no midvalve stack and just a pop off valve… but it will be very one dimensional. Once I learned to think of the base valve as just that the base that works for low suspension velocity situations. The midvalve is the speed sensitive or HSC for the fork during high suspension velocity situations such as whoops and consecutive jumps or rhythm sections. Two much midvalve damping and you get the dreaded mid stroke harshness too little and it will wallow down into the stroke and things get ugly that way too because there is only so much the base can do. It isn’t rocket science and as others have suggested pull your valve stacks apart and measure, take pictures, then order some additional “base shims” make sure they are the correct thickness as the rest and make some changes. Now the fun part, test, take notes, think about the direction you went and what changes you feel or can’t. Now guess what … do it all over again and welcome to the rabbit hole of working on your own suspension 😂

I’m running the same mid-valve stack as you and had to reduce the float to .05mm before the wallowy feel went away. That last little bit made a big difference. Went from bottoming everywhere to having 2” left with just that small change.

Adding an 8.10.10 shim between the pair of 8.10.20s would get you there.

My base valve stack is just Mx Tech’s 6-face shim offroad setting. So quite a bit softer than yours. This is a desert setup, so needed the small bump compliance of the offroad base but also g-out and whoop holdup of the stiffer mid.

Love these knowledge-sharing tech discussions. Taking notes. Carry on.

The base valve and mid valve work together to create a net damping force. The base valve only provides damping when oil is moved through it via the damping rod displacing volume as it slides into the damping chamber. The midvalve provides damping immediately as the fork begins to move because the mid valve is pushing "through" the oil. An important function of the base valve is to provide significant resistance to the oil flow so that it remains under positive pressure and doesnt cavitate as the midvalve is pushing through it. Base valve must create more positive pressure on the oil flow than any negative pressure behind the moving midvalve to avoid oil cavitation.

Most of the "control" is tuned in the mid valve on modern forks because it provides roughly 2.5x-3x the damping force vs the base valve. The base valve stack  is often spec'd against the mid valve stack so that it produces enough resistance to prevent cavitation. A stiffer midvalve requires a stiffer base valve to prevent cavitation. 

Because your damping force = base + mid, your clicker adjustments are really just adjusting that resistance on the base valve by allowing more or less oil to flow through, and this effects the entire damping force. Your fully soft compression clicker setting still should provide enough oil resistance to prevent cavitation (which would mean drastic loss of damping force and could be very dangerous).

There are some kits out there like the Kreft RC valve that allows adjustable mid valve settings, as well. 

Did you ever get these Ravens working better? Are they still blowing through the stroke?

So you can’t even change the oil in the cartridge without the special tool?

I feel kind of the same way. Ended up making my own tool to service them and it works fine. But it would be nice if they were more normal in that area. 
 

Regarding the valving, the midvalve change I posted above helped a lot, but they still move too much in the mid-stroke. I’ll be curious to hear what you think of the new valving. Did MX Tech include a spec sheet with the new setup?

Jeff at Over the Top Suspension in Visalia, CA has the tools to disassemble the MXT cartridges.  He actually put Blackjacks in my 17 FC350- your old Vintage inspired build.