does adding more LS comp make a shock feel smoother or harder?

[kevinstillwell]

Kevin would you try my stack on the dyno from the 05 rmz? it would have to be compared to std however?

40.15(20)

30.1

40.2(3)

24 Clamp

Hi Marcus,

First I need to know if you have ridden with this stack (I'm assuming so; as we don't want to dyno some obsure setting just to see what it does).

Then I need to know how it worked. Just a general observation is all that's needed. e.g. On the Valving DataBase I simply classify a stack as:

- poor (definately going to change it)

- ok (rideable, but could use improvement)

- good (good enough, doesn't need further adjustment)

I also need more build information to do a worthwhile dyno run. Below is a list of what I need. It may seem like overkill, but each of these things has an affect on the damping.

lsc

hsc

reb

nitro

oil

piston preload - i.e. did you surface either the comp or reb side?

piston band - is it new or used?

piston orings - are they new or used?

piston band bleed - does the piston band have a little bleed hole in it?

piston band od - it's a good idea to start measuring them as a quick check to make sure they are in spec.

shaft seal - is the shaft seal fairly new or old?

shaft bush - is the shaft bushing fairly new or old?

torque, comp adjuster nut - did you remove the comp adj nut (the nut to get to the shims), and if so, what did you retorque it at?

torque, shaft nut - what did you retorque the shaft nut to?

top out washer - did you replace or in any other way modify the stock top out washer (such as put fill shims between the top out washer and the base shim.

Might as well include the rebound stack.

Shoot me that info, and we can give it a go.

Regards,

Kevin

[skipn8r]

I downloaded this paper and checked it out. Pretty interesting.

Seeing that GM employees use something so "basic" as a tuning guide makes me wonder if a more comprehensive software model is even feasible...

[frezno]

i rather wonder when i'm reading that dyno tests don't give you a real world solution but you have to try various stacks on the track, why use the dyno at all for stack testing?

ok, that question might be a little provocative (or better: more provocative than intended/meant). I think a dyno result gives you some basics where to go or what's the wrong way but does it realy provide that much info that it's definitly a help finding stack settings?

But probably that's not the task of a dyno anyways?

[kevinstillwell]

i'm reading that dyno tests don't give you a real world solution but you have to try various stacks on the track, why use the dyno at all for stack testing?

I hear that question all the time. Of course, the dyno doesn't tell you what stack to run, and initially it won't tell you if a stack is any good or not.

In the real world, you need riders to test the settings. What the dyno does tell you is exactly what your valving changes are doing. This allows the tuner to adjust the damping curve in methodical and step-by-step increments. It doesn't totally eliminate guessing. You still need your knowledge of shim stacks so you can "guess" what valving changes are needed to alter the damping. The dyno simply allows you to verify that you have changed what you intended (if it didn't, you need to go back in and tweak it).

Now that seems simple enough. What the dyno also shows is how simple things like shaft nut torque, nitro pressure, surfacing pistons, piston preload etc. affect the damping. Every little thing contributes to the damping forces, and a tuner may be creating inconsistencies without realizing it.

We have also found that no two forks or shocks are exactly the same. There can be 50 - 100 lbs difference in two supposedly identical shocks. This is a big difference and would translate to + / - 10% or more. We consider a 4% damping change to be a fair amount to increase or decrease the damping curve. This amount is noticed by the rider. For comparison, the difference between a shock compression adjuster at 6 out vs. 16 out is about 1.8%.

So the dyno can tell you if your valving changes are doing what you want and if the damper is within specs.

Above I said "and initially it won't tell you if a stack is any good or not".

- If you dyno just one or two stacks, it doesn't tell you much.

- After you have dynod several stacks for the same bike, you begin to see patterns in the damping force curve. You see what are 'good' low speed force numbers and what are 'bad' low speed numbers. You see patterns develop and can begin to predict ahead of time how a particular damping curve may work.

Seeing that GM employees use something so "basic" as a tuning guide makes me wonder if a more comprehensive software model is even feasible...

On the same line of thinking, having hi-tech software that could model a dampers performance would be a great tool. But, just like the dyno, it wouldn't tell you how to build the stack. It would allow you to learn more about how the dampers work and would be a useful tool in analyzing two different damper settings.

"Knowledge is power".

Kevin

-

[mog]

Hi Marcus,

First I need to know if you have ridden with this stack (I'm assuming so; as we don't want to dyno some obsure setting just to see what it does).

Then I need to know how it worked. Just a general observation is all that's needed. e.g. On the Valving DataBase I simply classify a stack as:

- poor (definately going to change it)

- ok (rideable, but could use improvement)

- good (good enough, doesn't need further adjustment)

I also need more build information to do a worthwhile dyno run. Below is a list of what I need. It may seem like overkill, but each of these things has an affect on the damping.

lsc

hsc

reb

nitro

oil

piston preload - i.e. did you surface either the comp or reb side?

piston band - is it new or used?

piston orings - are they new or used?

piston band bleed - does the piston band have a little bleed hole in it?

piston band od - it's a good idea to start measuring them as a quick check to make sure they are in spec.

shaft seal - is the shaft seal fairly new or old?

shaft bush - is the shaft bushing fairly new or old?

torque, comp adjuster nut - did you remove the comp adj nut (the nut to get to the shims), and if so, what did you retorque it at?

torque, shaft nut - what did you retorque the shaft nut to?

top out washer - did you replace or in any other way modify the stock top out washer (such as put fill shims between the top out washer and the base shim.

Might as well include the rebound stack.

Shoot me that info, and we can give it a go.

Regards,

Kevin

WOW what a lot of questions

This is the best stack i ran in my 05 rmz 250, i tried 3 others before this, it was very nice IMO, it had a good plush feel and took acceleration chop and breaking bumps well enough, it would not blow through the stroke too easy and had decent bottoming resistance, however it would not work at a sx type track at all well, it would then blow through the stroke and bottom pretty hard.

LS 9

Reb 9

N2 160psi

Oil 5wt Pro RSF

Piston was all std

The shock was well used,something like 50 hours, didnt measure the od of the piston, sorry.It was bedded in lets say.

Shaft seal was also 50 hours use.

Compression adjuster was modded by removing a 14.3

I dont torque the adjuster nut back to a specific reading.

Shaft nut was 25lbft.

Top out washer was modded by removing the lip that covers the reb bleed.

Reb was std but i removed the clamp shim to make the stack clamp on the next bigger shim.

What you say about 2 shocks/forks varying a lot- i have found to be very true, my 05 rmz fork started out way too stiff, rigid even, could not get it plush, then after about 40 hours the thing got softer and softer and i could not get it to hold up in the stroke any more, had to keep adding compression shims etc, yet some were much plusher to start with.

[kevinstillwell]

OK, that should be enough into to go with. All that additional info I asked for is a bit much, but if you are going to do something, might as well do it right.

I will dyno your settings and also compare them to stock.

I will be a couple weeks before I can get the runs completed and the info put up.

Talk to ya then,

Kevin

[mog]

OK Kevin look forward to the results, thanks.

[frezno]

going back to the original question.

let's say there's an imaginary shock compression stack of a bunch of 40.20 (eg 14) and rolling down by two notches to 22

what if we place as very first shim a 20.10 or something small and thin like that.

wouldn't that make the initial (ls-) stroke somewhat smoother but give strength to the high speed?

[kevinstillwell]

Hi Marcus,

It looks like two weeks turned into two months. How time flies....

Anyway, here are the results from your dyno run.

I used the stock rebound stack so we could run the dyno at a faster speed. We use a 2000 lb load cell on the dyno. Your modified rebound would have exceeded 2000 lbs force, so we kept it stock.

(frezno, I would imagine any reduction to the low speed would reduce the high speed as well. There's only one way to find out. I'll run your suggested scenario tomorrow and we'll see what happens)

In the screenshot shown below, the dyno force numbers are in the table to the right.

ips = inch per second (speed of the run)

co = compression force in lbft.

There is also a column that shows the lbs diff and percent differences.

We mount the shock in the dyno and do 11 consecutive runs all in one set.

- the first run is at 1 ips. The dyno strokes the shock 3 times and figures and average force.

- the second run is at 2 ips, the third at 3 ips etc until the end.

[kevinstillwell]

let's say there's an imaginary shock compression stack of a bunch of 40.20 (eg 14) and rolling down by two notches to 22

what if we place as very first shim a 20.10 or something small and thin like that.

wouldn't that make the initial (ls-) stroke somewhat smoother but give strength to the high speed?

Hi frezno,

Good question. We ran a couple tests to see what happens . I used 10 - 40.20 instead of 14.

As you will notice in the screen shot, I always put the newest test as Stack 1, and the 'compare to stack' as Stack 2.

[kevinstillwell]

Here is another way to look at all the dyno tests together. I've sorted the 5ips force from lowest to highest. You can see how the different style stacks affect low speed and high speed damping.

Regards,

Kevin

[MRW]

One word "myth busters"!

[mog]

interesting stuff, its way different than i expected but a good excercise as people can now see a stack that gives the same low speed but less high, not actually what i was after but it rode good and thats what mattered, also mine and the single taper of frenzo are similar with mine having a little more high speed(a good thing IMO) however my stack costs a fortune in shims as no one uses 0.15s in a normal shock.

Many thanks for your efforts kevin, in future i think i will just alter the clamps as it so much easier LOL.

Kevin you going to MXDN?

Marcus.

[kevinstillwell]

No, I won't be making it, but it sounds like fun.

[but head]

stock pistons such as showa I notice they have a ton of shimms , after maket valve bodies seem to run a lot less shims I have moto pro kits and after installing them I find them to work real well and easey to tune

[MRW]

Hey guys I have a question about the current Showa`s BV assembly shim stacks.

Does anyone have an idea of the total stack deflection?

The only thing I have found was at dirtridernet where"JW", mentions total defection at about .035". This is just about the same distance between the last 30 x.10(LS shims)and the 30mm backing plate with stock valving. Is this dimension some sort of safety factor built into the valving? Say if a bigger guy jumps on an under sprung bike and jumps it big? Maybe the shims contact the plate and hydro lock?

I`ve seen "A" kit stuff and it is totally different setup for sure. I am experimenting with probable "high maintinace" stacks due increased backing plate distance. Just wondering if maybe this might not be safe in the long run:bonk: ? Thanks

[frezno]

Does anyone have an idea of the total stack deflection?

how do you measure this?

I've a set of BV's lying around and could take a look and/or modify it.

btw, the 08 BV's are completly different, no big fat piston but more like a soucer and much more shims as well (starting with 31 od's).

[MRW]

how do you measure this?

I've a set of BV's lying around and could take a look and/or modify it.

btw, the 08 BV's are completly different, no big fat piston but more like a soucer and much more shims as well (starting with 31 od's).

I guess the only way to measure "deflection during operation" may be to coat the backing plate with something that would wear off, blue dykem, paint ...whatever, when the shim stack hits it(backingplate). Some after market BV setups have really small backing plates in comparison to face shims(LS), so I guess I wont worry too much about "unlimited total defection" of the shim stacks.? But,with no backing plate the shim stack may fail, break or fatigue.

OOO, you have info on 2008 Showa`s!!! Show some pics Frez!

[MRW]

btw, the 08 BV's are completly different, no big fat piston but more like a soucer and much more shims as well (starting with 31 od's).

Seems like thier preloading the valve stacks? By "saucer" do you mean "dished"?

[frezno]

By "saucer" do you mean "dished"?

ooops, sorry for the misunderstanding.

With piston i didn't mean the shim-piston but the one with the bushings between ics and shimstack.

you'll see it in the pics

OOO, you have info on 2008 Showa`s!!! Show some pics Frez!

just servicing an 08 fork and pics will be online tomorrow