Jump to content
Sign in to follow this  

Technical question about shims

Recommended Posts

Hi, I would like to add a little bit of rebound resistance to a shock on my 03CR250. I was thinking the logical way to go is to add one more shim like the larger one sitting at the base of the rebound stack. I ride sand alot and need to make it stiffer. In general, is this a reasonable way of adding resistance, by adding a shim like the one sitting directly on the valve?

Share this post


Link to post
Share on other sites

Yes.

On the 03 there should be one 40.2 shim on the LS portion of the rebound stack. You may want to add two shims (I've seen as many as four added) as these shocks tend to be a bit quick on rebound.

:thumbsup:

Share this post


Link to post
Share on other sites

Thank you for the precious info. Priceless I tell you! I was thinking about adding shims until I get the best setting around the middle of my clicker adjustment. By adding shims like the one at the valve face do you keep the same overall damping profile, but just stiffer? Or there are some issues like compromised plushness...etc.

Share this post


Link to post
Share on other sites

If you slow the rebound too much, you will feel it when going over a series of whoops. The shock will not be able to completely expand between the peaks of the whoops and will cause a rougher ride. That's called "packing".

And remember, there is no one setting that will work for all terrains, speeds, and rider styles.

Have fun!

Ride on

Brewster

Share this post


Link to post
Share on other sites

Brewster, thanks for chiming in. However this is not the info I was looking for. I know what packing is and have no problem dialing it out. My question was how do I know when I have made the valve stack stiff enough. Is it when my clickers are somewhat in the center of their range, while I have them adjusted at optimal setting. I need to have a usable range because I use the clickers alot from one track to the other. Also, Should I expect a break-in time for the shims and tune a bit stiffer.

Share this post


Link to post
Share on other sites

No Hand

There are many reasons to address rebound issues. Suprisingly enough it is the area most overlooked by the greater number of tuners. Yet in turn, it can yeild the greatest gains. Given that rebound will affect your comfort, traction and feeling of control, it plays a very important role. As SC Spode pointed out there is limited control on the low speed rebound on your particular bike. Certainly a couple of additional shims will be of benefit. When setting up for sand you have to adjust the rebound for your requirements. Loose sand tends to offer little traction and forms whoops that are spaced 1 1/2 - 2 bike lenghts apart. This will require greater compression and a quicker rebound setting. Compactable sand forms choppy whoops that are spaced closer together. A slower rebound setting is more desirable in this instance. Knowing your requirements and being prepared to adapt is the greatest weapon you can have in your arsenal.

Share this post


Link to post
Share on other sites

Thanks for the info Terry, I can certainly understand the importance of rebound. Though, it must be harder and longer to fine tune than compression when building a shimstack. I personnaly don't do valving but I do clickers :thumbsup: and find it more subtle to tune rebound than compression using clickers. I was under the impression that when adding shims the lowest on the low speed stack that it would automatically stiffen the whole circuit because it is built from the low speed on up. Except with multi stage valving like here, I took for example the shock valving from the 05RM250 (Thanks to Bruce!!), If one would stiffen the LS rebound here by adding some 40.2 shims I guess it would only stiffen the LS rebound without affecting much the rest of the rebound damping because of the multi stage created by the 22.1 transition shim. Is it somewhat reasonnable or am I way out in the ditch :

shock

comp:

44.2(9)

38.15

30.15

42.15

40.15

38.25

36.25

34.25

32.25

30.25

28.25

26.25

24.25

22.3

21.3

30.3

plate

reb:

40.2(3)

22.1

40.3(5)

40.2

32.1

40.3

38.3

36.3

34.3

32.3

30.3

29.3

28.3

28.3

27.3

26.3

25.3

Share this post


Link to post
Share on other sites
Thank you for the precious info. Priceless I tell you! I was thinking about adding shims until I get the best setting around the middle of my clicker adjustment. By adding shims like the one at the valve face do you keep the same overall damping profile, but just stiffer? Or there are some issues like compromised plushness...etc.

I haven't noticed any effect on compression damping by adding shims to the LS rebound stack.

It would seem logical to want to center the adjuster to have the widest range of adjustability available, but as long as you're the only rider and you can find a setting that makes you happy, I don't know if it's worth the effort if the setting isn't at one extreme or the other. :thumbsup:

Share this post


Link to post
Share on other sites
I haven't noticed any effect on compression damping by adding shims to the LS rebound stack...
ok, I was also wondering, do you feel an impact on the HS compression let's say if you add shims to the LS compression stack. I guess this would impact from the LS all the way up, right :thumbsup: . Except if there was a transition shim to isolate the stages, is that it?
...I don't know if it's worth the effort if the setting isn't at one extreme or the other. :ride:
My rebound is 1 click from being all the way in when I'm at one track in particular.

Share this post


Link to post
Share on other sites

If your asking that when you add shims to the low speed does it effect the high speed too? I believe it does. It mostly effects the low speed but does effect the curve as a whole.

I had an 02 CR250 and had the same problem, in fact I had the same problem on my 04 CRF450. I had good luck with adding a little low speed along with a little bit bigger x-over and also taking away the bottom shim (25x.3) on the high speed stack of the rebound. That should let you open up your adjuster some for a better feel.

Good luck!

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  

×