comparing diff diameter damp-cartridges

georgieboy · Aug 28, 2003

to whom it may concern or likes to answer.
I own these marzocchies conventional 50mm forks. Nice forks but they were too plush all over the stroke. Just dropped tru the stroke when you jumped something small and wallowed a lot tru high speed.
After reading a lot here on this forum i decided to try to solve some of it tweaks by myself. I felt everything above was a low-speed movement of the fork, so i searched in that direction.
So, i did some silver solder to close 4 bleed holes along the cartridge to get a more "normall"cartridge damper. Now i have a cartrdige that is just like yr guys have(i think), and went on to fiddle with the shim stacks.
I tried 0.3 freelift at the midvalve but still found that they were to plush. This probably is because the comp clickers are working directly with the midvalve and so i can tune freebleed with the clickers. This is completely different to yr forks as you all have the clickers working on the base-valve.
Working along i measured the inner-diameter of this cartridge and came to 26mm.
Now my question is: what can you say theoritical about the difference in id of the damper-cartridges keeping in mind that you use the same shim-stack for diff id cartridges?
I understand that you all use bigger id cartridges. So what are the pros and cons about inner-diameters??
By the way, the push rod is 12mm.

DEANSFASTWAY · Aug 28, 2003

Theres a trend to bigger cartridges I guess and the bigger cartridge works more oil but youll likely to change lift or float on the Mid valve the bigger the cartridge . I dont really think you could run the same stacks on diff IDs if thats what youre asking/saying.It would make a different flow coefficient with a bigger cartridge. Cartridge rod size comes into play too. What did you solder up? Was the cartridge drilled in steps ?I used to seal the holes up also. It was like those forks were stricly specd for rocks or roots or something . Lots of bleed then comp starts 4 inches down. I used to have to fix alot of those type forks when I was at a Husky Shop they liked to leak.

georgieboy · Aug 28, 2003

Hoi Dean, i knew already that u have been working for that shop and doing marzocchies.
Years ago i solder the slot closed, and drilled those 4 bleedholes on progressive distances along the length.
But now i just closed these also.
Like you said it's looked like there was only damping the last 15 cm(4 inches).
Great for rocks though but i am evolving and becoming a faster rider(i think), and so my fork must evolve with me(grin).
By closing all the holes i now have compression from the very top of the stroke and now the clickers really work.
My question is just to figure out things, trying to understand what happens insight a fork.
To make it easier to understand i was hoping by keeping the shimstack the same for different cartridges, you guys cld make me understand what wld happen with a fork during it working cycle.
For example, what wld be the feeling in a bigger cartridge compared to a tiny cartridge. Wld the little cartridge lock up, and the bigger one be overly plush.
Wld a tiny cartridge need more freebleed to compensate etc.

DEANSFASTWAY · Aug 29, 2003

georgieboy I think youre on the right track.

georgieboy · Aug 29, 2003

ha ha ha yr suspension guys keep being political on these items.
But thnks anyway Dean, i appreciate yr answer.
It is what i thought.
I will just shuffle ahead and when in doubt i come back to the forum.

marcusgunby · Aug 29, 2003

A small rod diameter displaces less fluid, and so the base valve doesnt make such a big contribution to the overall damping.Large cartridge will produce more damping and so tend to use a larger lift.Eg showas lift 0.2mm KX KYB lift 0.7mm.You want to be able to compare settings for different forks but with sping rates, lift, port size, clamp shim diameters it becomes almost impossible.

georgieboy · Aug 30, 2003

Marcus, as i'm recalling right my rod has the same diameter as kayaba's etc. 12mm.
It is my cartridge which is smaller 26mm compared to nowadays standards.
So my rod is pushing a lot of fluid tru the basevalve. But because of the small mv piston it is prone to hydraulic lock.
Do you agree with me?
So i need to keep my mv stack light and my bv stack relativ strong.
By the way, is hydraulic lock merely caused by midvalves or is there also a possibilty that a basevalve wld cause it. Thinking about i wld say: only midvalve.
Pls correct me if i am mistaken in my theory.
By the way, (offtopic)saw some foto's of yr son. Great isn't it?

marcusgunby · Aug 30, 2003

Im trying to help but its hard never seeing what parts we are talking of,i would say it doesnt actually matter what size the catridge and rod is-as we can tailor the stacks to suit(eg a WP fork with a 14mm rod uses a 10mm clamp shim where as a KYB with 12mm rod uses a 11mm clamp shim-the stacks apart from that can be the same)-as long as your midvalve lift is reasonable-if you use something between 0.2 and 0.5mm with a reasonable stack you can then tailor the base valve stack to get it really good.The port sizes and distance apart play a huge part in the shim stack build so it will take some work and experimentation.

Im not sure i adgree with the idea of hydro locking-more likely it will cause a hard feel from excessive damping, this may feel a bit like hydro lock.I like low lifts and light stacks both mid and base, but i feel this does tax the shims more than a gold valve type setup.

 

Ross is great to come home to after a bad day-takes away your stresses:)

georgieboy · Aug 30, 2003

Marcus, time comes that Ross is really going to talk. That is funny, when you can have conversation with yr kid. Like you come home and he is saying:
Hee Dad, how was it at work?? Bad huh?
Okee back to the topic.
Sometimes i have the feeling that the whole basevalve idee is just not so important. I feel that everything is done with the midvalve.
I mean what else is the basevalve doing except for letting some oil pass that was pushed away by the the rod.
The midvalve is actually doing all the hard work.
So how big a deal is the basevalve, when you talking about tailoring made.
I mean can people really screw up a basevalve stack.
I suppose i just have to try and see.

marcusgunby · Aug 30, 2003

LOL i wonder how many readers are interested in our daddy talk:)

Yes you are right-the mid does most of the work(probably about 2/3 of the total damping)-however a bad base valve stack will ruin the feel of the fork-eg fit a bunch of 0.15mm thick shims instead of 0.1mm and you will feel the difference;)bruce will know about this one :) the lift has a massive effect on a fork so be carefull if you alter it-i stick with one lift on a fork, and then alter everything else-if you alter the lift much you have to start from scratch.

so yes the base is good for making the fork a tad softer/firmer etc-ive known some tuners to remove the stack from one fork leg to get the fork softer-so it does make a difference.Its time to get the impact gun out and have a play:)

georgieboy · Aug 31, 2003

Today i went riding and was satisfied with the fork behaviour.
The great thing about my marzocchies is(bear in mind that this is mine first real motorbike, so i cannot compare) that one leg is totally for compression and one for rebound.
That means that i have also clickers for the midvalve.
I am now riding with more spring pre-load and with no lift on the midvalve.
The fork is now firm but when riding i was suprised with its plushness.
Probably because i am now riding higher in the stroke.
I will now stay with no-lift for a while and will screw up my base to see what happens. 0.15mm shims you say, Marcus. I will post back next weekend.
Till than and thnks so far, u to dean, for sharing some thoughts with me.

comparing diff diameter damp-cartridges

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