I'm revalving my 45mm shivers on my 02 CR250

[Motosportz]

Got one apart and will start posting what is in there and what I am doing. Hope this will be a reference for those who want to try this themselves. Will post ride results as well obviously.

Been Chatting with Kyle Terry on this stuff and he suggested some valve stacks. Just measured stuff up and his recommendations are a long ways from what's in there. I;m looking for compliance in rocks and roots but dont want sloppy cornering. This to me seems like it means leaving the low speed about stock and making the high speed softer. then again it has been a long time since i did this stuff. Should be fun.

What i am assuming is stock. Here is what came out...

All in millimeters:

Dia - thickness

(4x) 23 - .010
13.91 - .010 crossover shim
21.93 - .009
19.98 - .010
19.00 - .010
17.00 - .010
14.96 - .010
13.92 - .010
12.07 - .009

Here is what Kyle sent me to try for the base valve and has been using single stack (no XO)

Base Valve:
22.1 (3X)
14.1
20.1
18.1
16.1
14.1
12.1
10.1

I dont think i have the shims here to do anything like that so might just wing it on the info I think i know.

Been reading a lot on the web and like this simple description of what does what.

http://www.supercross-online.de/Z/valving basics.htm

Based on this I'm thinking of removing one LS face shim and 2 of the high speed shims.

Note i am also considering drilling out the base valve holes as they seem super small and might impede flow but i know this will add another variable to deal with. Going to have these apart a few times i bet. Then there is oil viscosity and level to choose. Oh the fun of it all.

Will be diving into my mid valve as soon as i decide what to do with the base valve.

 

[Motosportz]

save

 

[Motosportz]

save

 

[Motosportz]

save

 

[Norman Foley]

Drilling out the base valve holes, is a pretty standard mod.

 

[Motosportz]

Drilling out the base valve holes, is a pretty standard mod.

I know and I can see why on these but more flow means different shims. I'm guessing at it all anyways

 

[Norman Foley]

I know and I can see why on these but more flow means different shims. I'm guessing at it all anyways

It's like a poor man's Race Tech Gold Valve. Maybe someone has the shim stack for that?

 

[TROFFER88]

I have the riders edge stack for the 45's with there base valves

 

[Kyle Tarry]

Kelly-

Can you give a little info about how the forks were working for you? Did they bottom? How much of the travel were you using in your normal terrain? Harshness? If so, at what speeds and/or on what obstacles?

One the base valve body, there is a little "shoulder" that the clamp shim sits against; on the Shivers, this is about 11mm. So, if the last shim in the stack ("clamp shim") is larger than this, the shoulder effectively becomes your clamp shim.

I can't see in the pictures, is there a little bleed hole on one of the ports? Some of these have it and some don't, but it effects the overall damping.

I would definitely recommend drilling those out. Opening up the ports actually doesn't really change the shim stack required, because you aren't changing the little "pocket" at the end of the port, and this pocket is the loaded area on the shim. Piston like Gold Valves or the Rider's Edge unit have a much larger area here, so they need to compensate (higher shim loading = softer stack). Be SUPER CAREFUL drilling them out. Don't let the drill bit get to the edge of the pocket or you will chip them.

This actually isn't too bad of an all-purpose stack. It is weird though, in theory I thought a CR was a MX bike, that is way too soft for MX. Kelly, was this fork all stock, or had somebody taken the nut off before?

My last question is whether or not you want to build a midvalve for these. The mid and the base need to work together, so one effects how you set up the other. Base-only is a lot easier, but midvalve gives you some cool tunability.

 

[ghte]

Kelly are you up to videoing your work. I know it would be a PITA but also a great reference piece

 

[Motosportz]

OK so I am finally done. Lots of interruptions and then lots of learning and assumptions. Might have just made a mess. I drilled out the base valve but there is not a ton of room so it is only slightly bigger. There is no bleed hole on this piston nor was there on my 04 CR125 I did gold valves on recently.

Here is what was on the base valve for the compression stack as mentioned above.

(4x) 23 - .010
13.91 - .010 crossover shim
21.93 - .009
19.98 - .010
19.00 - .010
17.00 - .010
14.96 - .010
13.92 - .010
12.07 - .009

Kyle, i had no way to do what you suggested nor was even close to what we thought might be in there. Seems like a very stiff HS stack to me. I am looking for plushness on roots and rock and more lower speed trail riding tight woods comfort. It seemed semi harsh on rocks and roots before and the compression adjusters were all the way out when I got it so the previous owner thought so too. I read a bunch of stuff on the web for referance and took a shot at it.

I removed two HS shims and one low speed and ended up with this...

(3x) 23 - .010
13.91 - .010 crossover shim
21.93 - .009
19.98 - .010
17.00 - .010
13.92 - .010
12.07 - .009

and the drilling of the ports.

I pulled the mid valve apart and also did not see what i thought i would. Four equal sized shims on the spring side and a rebound stack. I am unclear what is meant by float but am assuming is means the spring side shim travel? This was at 2.3mm which seems huge compared to some references although I did find some info where people said 2-3mm. Honestly I have zero idea what that does. I left the mid valve alone.

Topped them off to 125mm oil level with 7.5 wt.

Kyle, take a stab at what i should expect form my changes? The bounce up and down test in the garage they feel about right and I have a pretty good feel for the bounce test although I know this means nothing for high speed deflections like roots and rocks. We will see. This is for sure going to be an experiment.

 

[Motosportz]

here is some really good info on understanding mid valves. I'll see where I am at next ride and might dig back into the mid valve as it seems it affect high speed.

_________________

Midvalves

When a suspension compresses, the rebound piston and rebound rod displace oil, which move across the compression circuits. The oil can move through the rebound piston without causing any significant damping because the back of the rebound piston has a check valve, a spring loaded shim that allows oil to flow freely in one direction.

Midvalves are basically a shimstack at the back of the rebound piston to add an additional compression circuit. The difference between adding compression at the rebound piston versus adding it on the main compression valving is FLOW. The oil flow resulting from the rebound rod insertion, which flows through the main compression valving, is much less than the flow of oil through the rebound piston (depends on damper dimensions but typically 3 times less). This allows suspension designers to increase low speed compression dramatically and reduce the lag between the rebound rod entering the cartridge and the damping being created by oil passing through the main compression valving.

Midvalves may increase the compression damping significantly during low and medium shaft speeds but the challenge is to design a midvalve that does not create excessive damping on high speed events, a compression damping level that does not produce cavitation and midvalve shimstacks that do not distort permanently due to the high flow.

The most common midvalve design features a shimstack with a check valve and a set of travel limiting shims. Then the rebound piston moves through the oil, the check spring allow the entire shimstack to move away from the piston and allow some oil flow. This space between the shimstack and piston is called the gap or float. Because the flow is more restricted than a typical check valve, the low speed compression increases. On a higher speed event, the check spring allows the shimstack to move away from the piston again, but the increased oil pressure due to the higher shaft speed bend the shims and allow a much higher oil flow through the piston. The support shim (which replaces the checkvalve shim featured in a non-midvalve design) stops the shimstack from bending too much and permanently distorting. If the midvalve shimstack has a low stiffness coefficient, the high speed compression damping generated by the midvalve will be minimal and the fork will not feel harsh on square edge hits or jump landings. The sensation of support on low and mid speed events will be increased without the expense of restricting oil flow on high speed events.

Extra care must be taken when adjusting the compression settings on a fork with midvave. If the compression damping on the main valving is decreased, the chance of cavitation increases. Pressurizing the cartridge is an option, but if the compression damping levels do not require it, then why bother?

 

[Motosportz]

Here are pix of the mid valve for reference...

 

[Kyle Tarry]

Kelly, that's not a bad starting point. FYI, you can just round your shim diameters to the nearest mm, and the thickness to the nearest 0.05mm. So, your new stack would be:

(3x) 23 - .010
14 - .010 crossover shim
22 - .010
20 - .010
17 - .010
14 - .010
12 - .010

I'd expect it to be softer across the board, nothing drastic, but definitely noticeable. It will probably feel decent in the woods, it's not going to have a ton of bottoming resistance on big hits but that's probably fine for where you ride. If I had to guess it's still going to be a bit harsh on some embedded-rock type hits, depending on where you set the clickers. I'd set the clickers closer to the middle to start, if you open them way up I think you'll get a lot of chassis pitch. The bleed ports on those are pretty big, which is nice because you get a lot of adjustment range, but if you run them full open you get a lot of stack bypass.

A couple changes you could make if it doesn't quite suit your needs:

-Change 14x0.10 crossover to 12x0.10
-Add 10x0.10 clamp shim under the 12x0.10 that is currently in there.

A smaller crossover will help the face shims open easier for a plusher ride on trail trash, and the smaller clamp will help the whole stack flex more on bigger hits.

You could also get more creative and run a 3-stage stack for more progression.

Also, it would be good if you checked the rebound stack. I've seen some really whacky stacks on these forks, and I've seen some pretty reasonable ones, but that has a big influence on the way a fork feels so it's worth checking.

That's a typical Marzocchi checked midvalve right there. I don't know why they stack up 4 shims, there is so much float on those that the shims have basically zero effect.

That article that you posted has some good info, except they're off on the area difference between the piston and the rod. The piston on these forks has nearly 5X the area as the rod. More importantly, the effect of this is squared, because the base valve pressurizes the entire cartridge (both sides of the midvalve) and the only area it works on is the area of the rod, so the base valve is operating at a 20-25X mechanical disadvantage. This can be a benefit and a downside; it allows you to get very light, linear damping (which you can't do on a fork midvalve). It also means you need to create big pressures. While we think of (and treat) the fork fluid as incompressible, it's really not quite, and I believe that the result of this is a different "feel" from the two damping types. The base valve is a lot further away from the point of force application, and has a large volume it must pressurize.

 

[GMP]

I've done these over the years, GGs and couple Huskys. Husky quality is better than GG version inside, but pull everything down and check your inner upper tube anodizing! I have a set of new 48 CCs on my Beta, anodizing shot in 30hrs. I don't think Marzocchi in general uses a good process, as almost everyone I have taken apart has had worn uppers. Also, perhaps its the light/flash, but you piston band looks very "gold" which could mean the teflon is worn through, not good.

I had a real good setup on a GG 250. Build the midvalve with a 1mm float, use a .15mm face shim, and regressive stack for support. The thing with mids is the ones that work the best don't last as long. The .15 thk face shim helps this. Also no mention of your rebound stack. In my experience with these there is inadequate rebound control, and what you may think is a compression harshness is actually a high speed rebound spike.

 

[Kyle Tarry]

Awesome info GMP. I fully agree with your midvalve recommendation (very similar setup on my 610 was a huge transformation), and the rebound.

One small comment I'll make is that a couple of thinner shims see less stress for a given deflection (and stiffness) than one thicker shim; basically, it takes more stress to bend a thicker shim. It's also definitely important to have a backer shim on the mid to limit travel. The problem (as you mentioned) is that a woods mid works best with lots of travel, which beats the shims up.

 

[MOTORHEAD]

With the small ports of the zooks, you might as well convert the MV to a check plate and be done with it.

 

[Darkside]

I wanted to ask a question from you guys that know suspension. I read something about fork seal grease when putting in new seals. Do you guys use it? is it special grease or can I use bel-ray or silicon dielectric grease.
Thanks for any input.

 

[Motosportz]

Great info guys, thanks.

Got a short ride on the bike today in less than ideal conditions for testing. Heaving frozen ground and slick so had to ride nice. Was for sure a step in the right direction. Happy with the results and did pretty much what I was aiming for. I wanted to turn the comp clickers in which is odd for me. Found a sweet spot between 12-14 out. backed off the rebound some from mid settings. Rode a lot of rocky trails on purpose and was really please with the front, so much I hated the rear which did not seem bad before. Front glides over nicely with little deflection while the rear dances around. There is also a stupid big (and I'm sure heavy) 140 rear tire on this that has to go. I might rip the shock off and do a similar harshectomy.

Will post rebound stack shortly. You guy might be right in that in needs some love.

 

[Motosportz]

With the small ports of the zooks, you might as well convert the MV to a check plate and be done with it.

Not the first time I have heard that which it basically is at this point no?