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

Just curious. For those of you who have made valving changes, do you try to increase the low speed compression or lighten it to make the rear feel plusher?

i would say softening the valving makes it softer and hardening the valving makes it harder:bonk:

some other words for softening come to mind....lightening, reducing, decrease maybe even plusher to an extent etc and hardening.......harder, increase, stiffen, add etc

:thumbsup:

really though hardening the ls will also harden the hs which may allow you to run less hs which may "plushen" up the hs a little. but just hardening the ls is gonna make things harder all over moreso the ls (especcially on 2/3 stage stacks) imo and vice versa of course

I had to soften the compression valving on my 06 yzf 250 to make it feel plush, it beat me up till it did.

Just curious. For those of you who have made valving changes, do you try to increase the low speed compression or lighten it to make the rear feel plusher?

Kevin it's a somewhat baited question. Without an idea of a riders terrain and ability, low speed compression needs (roots at 1st gear slow speeds or rolling whoops in 3rd) could be widely interpreted.

Depending upon the existing shim format build, removing LS may not be ideal and could even be detrimental. It could be wiser to look more in the stacks center shims or even the MV if equipped to allow the LS to keep the bike well supported in many of it's other roles like under braking.

Just some thoughts.

PK

I will have to admit it's somewhat of a baited question, especially on the shock valving. I've run a bunch of dyno tests and am coming to the conclusion that you can't really alter just the low speed without it affecting the high speed as well.

It all started when I wanted to add more low speed comp damping and reduce the high speed at the same time (on a shock). I found it nearly impossible to achieve that combination.

well i used your old program to do the opposite, give me less low speed and the same high speed on my 05 rmz 250, it was the only shock setup i liked on that bike, all the others i tried ended up blowing through the stroke or just felt too stiff.

Mog, glad you were able to put the program to good use.

It's possible to keep the low speed softer and get the high speed stiffer. It's going the other way that's difficult.

i.e. Making low speed stiffer and making high speed softer.

Mog, glad you were able to put the program to good use.

It's possible to keep the low speed softer and get the high speed stiffer. It's going the other way that's difficult.

i.e. Making low speed stiffer and making high speed softer.

Kevin

As I'm sure you realize, there are several means to solve the issue.

Alter the aspect ratio of the shim stack cross section helps to a good extent. Or hand fabricate small diameter rigid clamps. Or consider a valve body design with either preloaded shims using two piece shims like WP has in some setups, or utilize a design similar to Traxxions or the new style Race Tech. Or alter one of the other in series circuits ability to flow during HS movements. Or build in a design that offers pressure blow off to eliminate pressure spikes.

PK

Hi PMK,

In this case, I'm just considering a stock shock piston, such as the KYB 46 or Showa 50.

Using the stock piston with different shim stack configurations is where I'm finding it difficult to increase the low speed compression while reducing the high speed.

I've also dyno'd different piston preloads using two methods:

- preload rings

- machining (adding), or surfacing (removing) preload from the stock pist

So far, neither of these methods are getting me what I want.

Alter the aspect ratio of the shim stack cross section helps to a good extent. Or hand fabricate small diameter rigid clamps.

PK

Could you elaborate more on these two suggestions.

-

If you slow down (stiffen) the high speed wouldn'y you be firming up the shock but also make it feel less harsh because it doesn't blow through.

When I had my shock done for the second time my complaint was that she still felt harsh and I couldn't get it to settle. The only change they made was to slow down the HS valving. Then I went in on the LS by 4 or 5 and the thing finally felt plusher and settled down.

Just trying to get a better understanding. Don't mean to hijack.:thumbsup:

Hi PMK,

In this case, I'm just considering a stock shock piston, such as the KYB 46 or Showa 50.

Using the stock piston with different shim stack configurations is where I'm finding it difficult to increase the low speed compression while reducing the high speed.

I've also dyno'd different piston preloads using two methods:

- preload rings

- machining (adding), or surfacing (removing) preload from the stock pist

So far, neither of these methods are getting me what I want.

Could you elaborate more on these two suggestions.

-

With the explanation of it being a rear KYB or Showa, and the things you would like to achieve, you might consider a check nut to isolate the rebound circuit on compression.

As for the other two, the obvious answer for an aspect change is bigger steps as you build the stack. A recent WP I pulled apart had an odd setup for rocks, it almost appeared they forgot the shims between the last 44 and the 38 that butted the 44. Basically it was a batch of 44's for "solid" LS, the HS was fewer total shims and a more unconventional jump in the stack.

The spacers are where you machine a small diameter clamp from round stainless, same as running a 6mm x 8mm shim in the BV of a WP. FWIW I've used the spacers in a fork but never a rear damper, could possibly be too much strain and fail since the piston is the stop in the rear. But it should run fine on the dyno.

PK

mikerides33,

So it looks like going stiffer on the compression, both low speed and high speed made your rear feel plusher.

My guess is that when your tuner stiffened the high speed valving, he also stiffened the low speed.

PK,

Good suggestions. I may save the stainless clamp for later.

I've tried the check nut (isolating or limiting the rebound adjusters affect on compression), and had decent success with it, but I'm trying to achieve similar results simply by altering the shim configurations.

The WP setup sounds a bit odd, but I don't see why it would't work. Gives me a few things to try in my spare time.

Regards,

Kevin

I've been looking for ways to predict similar adjustments. I came across a paper (SAE 2006-01-1380) that uses shim dimensions to calculate general damping parameters that can be useful as very general tuning guides. The paper presents calculations that make use of the fact that shim deflections are related to t^3 for small (low speed) deflections and t^2 for larger (high speed) deflections. The results of the equations are relative between two stacks and give percentage increase/decrease in damping for "high speed" and "low speed" damping. The way the equations are presented, I haven't been able to apply them to stacks with crossover arrangements, but I have run some standard taper stacks. Considering an OEM '05 RM250 fork BV compression stack, the stock arrangement is:

15x30.10

2x29.10

28.10

27.10

26.10

25.10

24.10

23.10

22.10

21.10

20.10

If I can believe my implementation of the math, one way you can achieve an 10% increase in "low speed" damping along with a 3% decrease in "high speed" damping is by going with something like:

1x30.15

8x30.10

29.10

28.10

27.10

26.10

25.10

24.10

23.10

22.10

Again, the equations are highly generalized and I've done zero testing to try and confirm the results. Not really sure of how to apply this to a shock yet...

I was going to say the way i would think it would go is this, a stack of much thicker shims on the low speed but less of them

this is a std kxf stack 2004

11-40.2

34.1

30.1

40.25

38.2

36.2

34.2

32.2

27.2

23.3

if we goto this

40.3(4)

34.1

30.1

40.25

38.2

23 clamp

we got more low speed on less high speed?

about 10% more low speed and 10% less high?

at least theory says we do

so kevin does this theory not pan out in the real world?

marcus.

I've been looking for ways to predict similar adjustments. I came across a paper (SAE 2006-01-1380) that uses shim dimensions to calculate general damping parameters that can be useful as very general tuning guides........

If I can believe my implementation of the math, one way you can achieve an 10% increase in "low speed" damping along with a 3% decrease in "high speed" damping is by going with something like............

...

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

I can't give away all my secrets, but here are a few random thoughts:

1. A 10% change in shim load does not translate to a 10% change in damping forces. A quick estimate might be 10% change in shim load = 2% in damping force differences.

2. A shim stack doesn't really deflect that much on the larger diameter fork base valves. This would also reduce the potency of a 10% change.

we got more low speed on less high speed?

about 10% more low speed and 10% less high?

at least theory says we do

so kevin does this theory not pan out in the real world?

marcus.

3. Marcus, I think you're refering to the % changes as you might see on the Shim Program. Shim stack calculations such as those done on the program and those done by skipn8r give you a rough idea of the relationship of the two stacks you're comparing, but things really change once you get them in the damper.

4. At one time I thought of calibrating the program to the actual damper forces, but have given up on that idea. It would be easier to dyno test 40-50 actual shim stack configurations, and then simply chart the stacks based on the low speed and high speed forces (I've actually started going that direction).

- Then, instead of using the program to calculate changes, you just pick a valvestack on the list that matches your criteria. You could go by the shim stack configuration and also the dyno force numbers.

- I think this would be a good way to compare stacks because so many tuners are used to predicting valving changes based on the shape or arrangement of the shims. They're not used to associating any numbers with the stacks, which I think would be very helpful.

Getting back to my original thought. With the stock piston and shim stack configurations I've found that they can be tuned to have more low speed. After you achieve that, it looks like your stuck and you can't get any more low speed (without increasing high speed) unless you go with piston changes or other type of modifications.

So if anyone's got a 'tried and true' stack that goes this direction (i.e. more low speed and less high speed), I'd be willing to throw it on the dyno and test it out. A shock would work best, because the fork midvalve makes a fork a completely different animal.

To make the dyno testing easier we have shocks for most Honda, Kawasaki, Suzuki and Yamaha dirt bikes (both mini and big bike).

Cheers,

Kevin

Kevin

One concern I had a longtime back with the program, and this did tend to focus more with HS issues, was that each added shim has the fulcrum radius change which is very difficult to predict. With that said, it leads me back towards a fabricated small diameter clamp or some very narrow shims to provide the least amount of HS support.

Your other option might be looking into the compression adjuster and altering some of the shim formats or other bits inside there. Is this something more than you planned to adjust?

Out of curiosity, which Rhoerig do you now own and what is the max IPS it's capable of. I wondering how much value you program for HS to decide where you are classifying it as HS. less than 50IPS, 50-75IPS, 76-100IPS, 101-125IPS, 126-150IPS or >150IPS.

PK

Your other option might be looking into the compression adjuster and altering some of the shim formats or other bits inside there. Is this something more than you planned to adjust?

In my search for more low speed (without increasing high speed), I want to fully explore the stock piston and shim stack configurations. But, I'm not stopping there. I plan on trying just about anything that seems feasible.

I've tried piston preload, preload rings, different pistons and some other odd setups. For a Showa 50mm shock, I actually made a setup once that used only 1 - 44.20 shim to cover the compression ports on the piston. I did the rest of the damping with the compressson adjuster. This was awhile back, but I do remember how plush the rear felt.

Out of curiosity, which Rhoerig do you now own and what is the max IPS it's capable of. I wondering how much value you program for HS to decide where you are classifying it as HS. less than 50IPS, 50-75IPS, 76-100IPS, 101-125IPS, 126-150IPS or >150IPS.

We currently have a 10vs, which is capable of reaching 70ips on shocks, and 120 ips on forks. If things keep going well, we'd like to get an EMA.

Forks and shocks can reach some pretty high velocities under extreme conditions. We don't try and tune for the extreme, but go for a good average. As a rule of thumb we use:

- shock max velocities = 100 ips (2.5 m/s)

- fork max velocities = 200 ips (5 m/s)

So with the dyno we can get 70% of the range on the shock and 60% of the range on the forks.

The dyno curve tends to get linear after the mid way point, so you can kind of predict where your high speed is going. I look at the compression damping curve in three ways.

1. 1-4 ips. These comp numbers tell me how the shims are opening.

2. 5 ips. I use these force numbers for LS.

3. 60 ips. I basically use these numbers as the HS.

60ips is really closer to mid speed. But, if I add shims to increase the HS, it is going to increase the MS as well. So you can just watch it at 60ips to see where the HS is going.

So when I say I want to increase the low speed and keep the high speed the same, I'm looking at it like this:

-- starting dyno force numbers (compression)

5 ips = 160 lb (LS)

60 ips = 750 lb (HS)

-- if you add shims to increase the LS by 10%, it usually increases the HS by the same amount

5 ips = 176 (+ 10%)

60 ips = 825 (+ 10%)

-- the difficulty is getting the 5 ips to 176 lb and keeping the HS at 750 lb.

Anyway, sounds like a personal problem to me. :thumbsup:

I've chatted with quite a few tuners who have dynos. Most make their tuning adjustments in the 0 - 40 ips range. They say that is what the rider feels most. Anything beyond that and it's bottoming control. Personally, I like to go as far into the velocity range as possible. The EMA will be good for that. Unfortunately, they're pretty pricey.

-

1. A 10% change in shim load does not translate to a 10% change in damping forces. A quick estimate might be 10% change in shim load = 2% in damping force differences.

Kevin

Thats a surprise to me but not a problem really, as a 10% change in shim load is something i can feel, if that translates into a 2% change in damping its interesting but just a number, however i can see with the forks you may need to go further to get the change in feel, a useful thing to know overall.

So in a way you are going to come up with a valving chart similar to a RT one but for std pistons, not a bad thing IMO.I would love to play on a dyno with different stacks to see how things work out.

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

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