Jump to content
Sign in to follow this  

how may shims need to be changed to notice a difference?

Recommended Posts

Here is a question for those that have done some shim-swapping. Taking a shock for example, how may shims need to be changed to notice a difference?

For example, if you take your existing shock setup and add two more shims off the face of the piston, is that enough?

Share this post


Link to post
Share on other sites

Depends on what's in there and how far off you already are. If you have a bike valved for a 200 lb SX rider and are going to use it for enduro work under a 140 lb rider, then you might need to change a LOT of shims before feeling improvement. In a normal setup though you should be able to feel the changes from 2 shims, possibly even one (again, depends if your current setup runs 5 face shims, or a dozen).

Share this post


Link to post
Share on other sites

i think on shock rebound one 0.20 make a difference you can notice a difference

on compression a sensible rider ear difference at one 0.20 face shim and many rider i ve revalved i think 0.25

Share this post


Link to post
Share on other sites
For example, if you take your existing shock setup and add two more shims off the face of the piston, is that enough?

As long as shim thickness is over .15, then yes.

Share this post


Link to post
Share on other sites
Depends on what's in there and how far off you already are. If you have a bike valved for a 200 lb SX rider and are going to use it for enduro work under a 140 lb rider, then you might need to change a LOT of shims before feeling improvement. In a normal setup though you should be able to feel the changes from 2 shims, possibly even one (again, depends if your current setup runs 5 face shims, or a dozen).

I agree here, how far you are off is the key here IMO.

I think the shock would be harder to feel than the forks. A lot beginner riders will run a shock without any nitrogen and can't tell a difference. I think in the fork, you remove 1 or 2 shims and you can tell a difference. But the shock would be harder to tell. I think it all boils down to how sensitive you are.

Great topics Kevin!

James

Share this post


Link to post
Share on other sites

one shim.

change the clamp on compression by 3mm

huge difference

Share this post


Link to post
Share on other sites

Notice I asked how much shim change is needed to notice a difference, not to improve it. And it does depend on how sensitive you are. The best, and possibly only way to be able to notice changes is to do a LOT of testing.

This is for a shock then. This is what I'm gathering from the comments so far.

Shock compression:

- two face shims should be noticeable if they are over .15's, and possibly one face shim if you are 'sensitive'.

- you would definately notice a 3mm difference in the base shim (clamp)

Getting into the high speed stack, how much of a shim change do you think is needed to notice a difference? And for now, let's keep the same separator and base shims (transition and clamp).

This is leading some where.....

Share this post


Link to post
Share on other sites

if you just changed the thickness of the crossovers, you would initiate a noticeable change. say from .15's down to .10's, and kept the same diameter of the shims. if you were to change the diameters of the crossover shims, that would also make a big change. if you went to one crossover from two.

Share this post


Link to post
Share on other sites

I think the original question is too simplistic without some qualification or detail. As I see it, it depends more on the existing stack and on the role of the valve in question.

Adding or removing one shim in a KYB shock rebound stack with 12 36x.15's in it would most likely go completely unnoticed, but doing the same with a compression stack that has 7 40x.20's would probably have a much larger effect.

Taking a midvalve stack with only 3 20x.11's and changing that by one shim would likely do a whole lot more than a one shim change to a base stack that starts with 17 32x.11's, too.

And, as mentioned, the role of the shim in question bears on the matter, too. The diameter of the clamp shim would be more likely to have a noticeable effect than changing one face shim.

Share this post


Link to post
Share on other sites

I have a stock 11' yz 450 and want to add some rebound and possibly some compssion, should i start with say two face shims on rebound and one on comp ?

Share this post


Link to post
Share on other sites

It would be helpful if you stated your weight and whether you are using the stock springs, and even more helpful if you knew what the stack looked like exactly, but just taking a known '10 setup as an example, the first 3 rebound face shims (40x.20) I would replace with 40x.30's. This particular bike had a more complex mod to the compression stack than just adding face shims, and I don't know that simply dropping another 44x.20 on the stack would do something for you that you would like.

Share this post


Link to post
Share on other sites

grayracer, I am using the bike to race cross country/gncc type races, I am 103kg's excluding kit, the rear spring is a 5.7 and on my 250f I got away with a 5.4 so i am sure it will be ok,

I am going to ter the shock apart next week to see whats in there

Share this post


Link to post
Share on other sites

I'd say your springs are a bit light for you at .47/5.7. Probably be happier at something like .49/5.9. Having the springs too light makes the damping do too much of the work, and it makes it just about impossible to get things working well.

Share this post


Link to post
Share on other sites
I think the original question is too simplistic without some qualification or detail.

The initial question was a little ambiguous. Let me rephrase it with more details.

1. I'm just trying to get a rough consensus on how big of a shim change is needed for the rider to notice a difference.

2. To keep it simple, lets just pick a Showa 50 shock with 18mm dia shaft, such as from the 2011 RMZ 450.

3. And we'll stick to the compression stack for the 50mm piston.

4. For example then, here is the stock compression stack:

7 - 44.25

44.2

37.15

24.20

44.3

42.3

40.3

38.3

36.3

34.3

32.3

30.3

28.3

26.3

25.3

24.3

23.3 b

5. And to keep it simpler yet, lets NOT change the 37.15 and 24.20 crossover shims, and NOT change the 23.30 clamp shim.

6. So now my questions are:

- how much of a shim change is needed to the low speed stack, and the low speed stack only for the rider to feel a difference?

- how much of a shim change is needed to the high speed stack, and the high speed stack only for the rider to notice a difference?

Like I said, I'm just trying to get a general consensus.

Kevin

Share this post


Link to post
Share on other sites

In my own experience, a 10% (or more) change in damping is needed for most to positively feel the effects.

Share this post


Link to post
Share on other sites

37.15

24.20

44.3

42.3

40.3

38.3

36.3

34.3

32.3

30.3

28.3

26.3

25.3

24.3

23.3 b

6. So now my questions are:

- how much of a shim change is needed to the low speed stack, and the low speed stack only for the rider to feel a difference?

- how much of a shim change is needed to the high speed stack, and the high speed stack only for the rider to notice a difference?

Like I said, I'm just trying to get a general consensus.

Kevin

44.25

42.25

40.25.....Something like this I can start to feel a softer transition.

38.3 I usually make a change like this with at least the first 4 shims to be

36.3 worthwhile change.

34.3

32.3

30.3

28.3

26.3

25.3

24.3 Less noticeable a .25 change coming up from the bottom unless the clamp diameter is involved.

23.3 b

Share this post


Link to post
Share on other sites
The initial question was a little ambiguous. Let me rephrase it with more details.

1. I'm just trying to get a rough consensus on how big of a shim change is needed for the rider to notice a difference.

2. To keep it simple, lets just pick a Showa 50 shock with 18mm dia shaft, such as from the 2011 RMZ 450.

3. And we'll stick to the compression stack for the 50mm piston.

4. For example then, here is the stock compression stack:

7 - 44.25

44.2

37.15

24.20

44.3

42.3

40.3

38.3

36.3

34.3

32.3

30.3

28.3

26.3

25.3

24.3

23.3 b

5. And to keep it simpler yet, lets NOT change the 37.15 and 24.20 crossover shims, and NOT change the 23.30 clamp shim.

6. So now my questions are:

- how much of a shim change is needed to the low speed stack, and the low speed stack only for the rider to feel a difference?

- how much of a shim change is needed to the high speed stack, and the high speed stack only for the rider to notice a difference?

Like I said, I'm just trying to get a general consensus.

Kevin

here's what could make a noticeable change: take the .30x44 and move it to the low speed stack. remove the .30x42 altogether, and leave everything else alone. the hs would then start with the .25x40. that would be a change the rider would feel. those are the two shims i would deal with. excluding the crossover shims, and clamp.

Share this post


Link to post
Share on other sites

On that stack, most riders would notice 2 face shims gone or added.

On the high speed - changing any 3 of the shims in succession from .3 to .25 would easily be noticed.

AKA

26.25

25.25

24.25

Or

28.25

26.25

25.25

Heck any three shims period in the H/S

Really sensative testers with true back to back to back on quick turn around can notice less change, but not always pinpoint what.

Many riders can truly feel 2-3 clicks no two things of it...which is small percentage.

But in those cases the suspension has to be close enough to not have glaring faults - ie a 250 pounder on a stock bike sort of thing.

He would not care all in or all out on the clickers - it just sucks period.

Addition:

In this particular bike, it has a really aggressive low speed setting. Changes to the stack are noticed but the end result of the rider feedback may state it still has "issues" that arent solved via stack changes...you can really chase your tail on this bike getting what you want in the rear.

Share this post


Link to post
Share on other sites

It would all depend on how far the current stack is "off". If the LS clicker adjustment is almost closed, you know it would take a higher percentage added to get it to a range the rider can work with, when he or she goes to various tracks.

The same way if the clickers are all the way open.

You would want a setup that the rider can tune thier suspension externally for

various terrain to some degree.

So for this exercise, If the clickers are all the way closed and the rider needs more ls, I think 2 or 3 added would be a good start.

HS I would leave alone in for this stack.

Share this post


Link to post
Share on other sites

the first shim in the hs stack IMO is very critical to hs where you could remove the 2nd last shim and probably not notice it , 2 face shims on the low speed is enough IMO , one is noticeable but not much use if you have enough clicker range

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×