relation between midvalve and basevalve stacks

[georgieboy]

Am I correct in thinking that i build my midvalve stack to compensate high-speed hits and that i use the base-valve stack to adjust bottoming resistance?
When yes, I want light low-speed valving for high-speed hits(midvalve) and i want heavy low-speed valving for the basevalve?

 

[marcusgunby]

The mid and the base can be used to adjust for most speed ranges, but the mid is better at controling mid and upper fork speeds.They really do work as a pair to cover the speed ranges.I try to not use the mid or base too heavily.

 

[georgieboy]

Thx Marcus,
can you perhaps explain why the 2004 KTM fork valving exist of only low-speed shims at the midvalve? Does this "rule" not work for WP forks?

 

[marcusgunby]

Cant explain anything about WP stuff as i dont think they have a clue why they do stuff like that.They should strip down a showa or kyb and see how to build a proper mid valve.

 

[georgieboy]

Oke that will do (how do i insert smillies, and winks ha ha ha)

 

[prcucuma]

As I have only looked into WP forks you might give me a clue how a "properly" built mid valve looks like compared to a WP one...

 

[marcusgunby]

Nice tapered stack with lower lifts for the cartridge size-for a KTM i would say 0.4mm lift is reasonable-you could go lower lifts but you will need to run a very soft base stack.

 

[dbrace]

The 04 125 sx has a more normal, tapered stack in the midvalve but still with lots of lift.

 

[JTT]

I had a 43mm WP (GasGas) apart the other day and they're nothing but a check plate with huge lift.

 

[marcusgunby]

LOL typical Wp-put a tapered stack in, but give it soo much lift it does nothing.

 

[georgieboy]

Nice, that this topic continues.
I myself did some fiddling again with my midvalve yesterday-evening.
Built a nice light midvalve stack, and a more heavily base-valve stack.
With turning the clickers at the base i felt great difference in compression from fully out untill fully in. The first time i really felt a difference. Great.
So now i feel i can do some tuning at the track, for bottoming resistance and riders feel.
I built my midvalve without !!! lift. This is because i have a second clicker that works for the midvalve only(marzocchie 50mm conventional). So i can create midvalve lift with my clicker. Great isn't it??
By the way, isn't it possible for the wp's to use the rebound clicker aswell for compression alterations? I mean doesn't the oil flow goes tru the damper rod, aswell in the compression stroke as the rebound stroke?

 

[georgieboy]

Last weekend i had the chance to ride a crf450. It makes me sad to say, but mine marzocchi suspension is not acceptable right now.
After only a few yards i realised that this was how suspension shld work. No hits at all on square edges.
Now i know that my suspension is really slowing me down. It just hits my hands on the square bumps.
At least now i know what to look for.
As i mentioned i had no lift at the midvalve. So now i go for lift.
Any one can give me a hint for the amount of lift.
Cartridge is 26mm id.
By reading the archives etc i must think of 0.5mm and less.
Right now i use 0.2mm(just put two 12x.1mm shims against the piston)
I understand that my midvalve sees low swept volume of oil because of that small cartridge. The rod is 12mm.
O and by the way, Marcus. As you are saying to try to keep yr stacks light, i assume that you have to increase oil height to compensate for bottoming??

 

[Jeremy Wilkey]

Gentlemen,
Midvalves and basevalve relationship is like the relationship of the shock piston and the compression adjuster. The Dynamic that ensues is quite interesting. If you where to build a fork or shock on a dyno and create some tests you can map out the relative areas where each valve and combo exerts influence on the total system. I have done this and its quite a cool little demonstration.

The midvalve + basevalve = Overall damping coefficient.

So to prove that build a midvalve with no shims only one very soft check valve, you get the front part graph and not much else through the middle and then if you can push it fast enough you get an interestingly steep tail.

To test the base-valve do the same only no basevalve shims, although you do have to pressurize the system somewhat. You get the midsection of the graph. If you place the top graphs on top of each other the sum is the overall coefficient. Of course through tuning you can overlap on region to another like Marcus points out, and interestingly this is where piston design really becomes apparent.

In the midvalve for instance if you have smaller areas of the piston then the less effective your Midvale becomes as it produces more fluid pressure, and larger deflections making the shims less able to control the area of the valve. The greater the area the less float you can run. I've found that on a wagon wheel midvalve of the WP you can easily run .2 float, yet by way of comparison, on the Showa with less area and smaller volume you can still only run .15 to .2 You would expect with the massive reduction of fluid in the smaller Showa Cartridge you could run almost no float, but it does not work that way do to valve design.. My point is each one of these different designs requires different lifts etc..

If your inclined to make blanket statements the smaller you can make the pivot shim and the lower the lift you can run the better your suspension will work. As your average damping coefficient will be lower and the feel more consistent.

 

[georgieboy]

thnks for shining some light into the darkness.