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DRZ Fork Revalve - Shim Stack Discussion & Recommendations

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I own a 2000 DRZ-400K, and while search for fork tuning information I found that there was a lot of discussion, but not a lot of actual information about setups that people are running. I've dug into my forks and made some changes, so I wanted to post the information up here in hopes that people may be able to find it and try it themselves.

 

My DRZ is a 2000 kick-only model, so it has the higher compression motor, FCR carb, and is relatively lightweight (supposedly ~260 lb dry). I weigh 170 without gear and am a C-level racer. I use my DRZ for aggressive trail riding and dual sporting out west, primarily on rocky CO terrain but also in UT, NV, and Mexico. I am running 0.48 forks springs, which have about the right sag with a large gas tank and all my gear on, but the front of the bike was still soft.

 

The Showa conventional forks on DRZs are good quality units, but the factory valving leaves a lot to be desired if the bike is ridden moderately fast. Due, in part, to the deactivated midvalve (which has a simple sprung checkplate stock), the forks blow through their travel and bottom easily, feel soft and wallowy, while not necessarily being plush on trail trash. The stock DRZ base valve stack is:

 

24x0.1 (6X)

15x0.1

24x0.1

22x0.1

20x0.1

18x0.1

16x0.1

14x0.15

12x0.2

9x0.2

 

If you plug it into restackor, the graphs look like this:

 

StockForkComparisonDRZ.jpg

 

For reference, I've compared it to a few other bikes: Husky WR300, TXC310 and TE610, and Yamaha WR450.  I picked these for a few reasons: first of all, this is the data that I have.  Second of all, these bikes (especially the 610 and the 450) are roughly the same size/type of bike, being medium size thumper dual sports.  Most of the bikes have two lines plotted; one line for the base valve damping ("BV") and one line for the total damping.  The DRZ, WR450, and TE610 are base-valve-only forks in stock form; in other words, the midvalve is checked.  The WR300 and TXC both have active midvalves in factory form.  For the midvalve bikes, it's important to look at the total damping, because the extra work that the midvalve does can make the base valve only misleading.

 

We can see that, out of all of these bikes, the DRZ is by far the least damped.  If we were to plot a motocross bike on here, the difference would be even bigger, since these are all either dual sports or trail bikes.  This isn't to say that one of these particular curves is "right," but rather that the DRZ is at one end of the spectrum, and bikes like the 610 and WR450 feel "pretty good" in stock form as far as striking a reasonable balance between plushness and control.

 

You could build a midvalve for a DRZ, but that requires tracking down a bunch of parts (spring, cut washer, sleeve, shims) that not everybody may have access too. Instead, I decided to just work with the base valve, which is much easier to get to and simpler, and should be easier for more people to work on.

 

Over the course of this thread, I (and others) have posted lots of shim stacks.  I started with some "weird" 3-stage setups, and gradually made them simpler over time.  I have edited this post to show the newest/most recent thinking for valving.  If some of the other posts don't quite make sense, this is why.

 

Below are 2 recommended shim stacks for DRZ riders for general use.  These should work well for trail riding, dual sporting, and slower racers (like me) on normal woods terrain.  The first stack is a relatively simple 2-stage stack, and the second is a fancier 3-stage stack designed to be more plush on rougher terrain.

 

DRZ Revalve #1 (2-stage stack):

 

24x0.1 (6X)

12x0.1

24x0.1

22x0.15

20x0.15

18x0.15

16x0.15

14x0.15

12x0.2

 

To build this stack, you remove the stock 9mm clamp shim, change the crossover to a 12x0.1, and replace all the high speed shims with 0.15mm thick shims (except for the first 24x0.1).  This is similar to (but lighter than) the WR450 stack.

 

DRZ Revalve #2 (3-Stage Stack)

 

24x0.1 (4X)

12x0.1

24x0.1 (4X)

18x0.1

12x0.1

24x0.15

22x0.15

20x0.15

18x0.15

16x0.15

14x0.15

12x0.2

 

Here is a ReStackor simulation showing how these stacks compare to the stock stuff:

 

RevalveForkComparisonDRZ.jpg

 

You can see here that these stacks give approximately 30-40% more damping than the stock DRZ stacks, and line up fairly well with some of the other bikes pictures.

 

For other purposes, you can change these stacks to your liking.  For example, for MX and sandy whoop use, member MarekB has run a stack with 10X 24.1 face shims and no crossover (single stage).  If you're a heavier rider and/or want to ride jumps and whoops, I'd recommend using the #1 revalve with more face shims; 8-10X face shims is probably a good starting point.  For supermoto (on the non-USD bikes), these #1 stack would probably work much better than stock, but more stiffness might be required, and you could try removing the crossover.  If you're a slower trailrider and you want a plusher ride, try the #2 stack but with 1-2 less 24x0.1 shims, and/or a 10mm clamp under the 12x0.2.

 

To build a fancier, more modern setup, you can retrofit the midvalve parts and run a "real" active midvalve like most newer bikes run.  If you want to do this, you'll probably want to run a softer base valve to go with the stiffer mid; see these posts for some starting recommendations:



 

For some info about the WR450 shim stack, and a similar stack you could try in a DRZ, see this post:


 

For some very good shock revalaving info, see BMWPowere36m3's post here:


 

For another perspective on some stiffer stacks for a DRZ, see this post by MarekB:


 

And, just some other options:



 

Good luck!

 

Shim stack reference points:

 

TE610 (2006) Stock BV:

23x0.15

23x0.15

23x0.15

14x0.1

23x0.15

21x0.15

20x0.15

19x0.15

17x0.2

15x0.2

13x0.2

 

WR300 (2012) Stock BV:

24x0.11

24x0.11

24x0.11

24x0.11

24x0.11

24x0.11

12x0.11

22x0.15

20x0.15

18x0.15

16x0.15

13x0.15

11x0.25

18x0.5

18x1

 

WR450 (2005?) Stock BV:

24x0.11 (12X)

22x0.15

22x0.15

22x0.15

20x0.15

18x0.15

16x0.15

14x0.15

12x0.15

11x0.25

18x0.5

18x1

Edited by E.Marquez
OP requested edit 25 Feb 14
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Glad to see you sharing this information over here :cheers: Could you post the graph in terms of damping force (lbs) in addition to the one you already have. When speaking of progressive, digressive or linear behavior of a shock/fork I think you want to look at damping force over velocity.

I finally picked up a set of E forks, so I'll be able to experiment too. I would like to see a 2 stage stack, 3 seems overall complicated (at least from what I've read, but there are many ways to achieve the same goals) especially in terms of understanding the stacks function. I wonder if there would be any benefit to opening up the bleed orifice in the piston to bring down that initial spike in damping.

I can't wait for more feedback from other members as well. Here's a piece from a resident guru I found early when searching for info here:

.48 fork springs,5.7 shock spring.

for what type of riding? most situations need the following-

forks need more low speed compression dampening,the oil level set at 100mm,10wt fluid.

the shock needs more low speed rebound,reduced high speed compression.5wt fluid.

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I took some measurements of the BV ('03 DRZ400S) and wanted to confirm the inputs you are using (shim stack is the same as you posted).

Compression-Side

  • Drod - 12 mm
  • Dvalve - 28 mm
  • wseat - 0.75 mm
  • Rport - 5.75 mm
  • Dport - 5 mm
  • Wport - 5 mm
  • Nport - 4
  • Dbleed - 2.19 mm
  • Dleak - 0 (no leak ports within the piston)
  • Dthrt - 3.89 mm
  • Nthrt - 4

Edited by bmwpowere36m3

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Could you post the graph in terms of damping force (lbs) in addition to the one you already have. When speaking of progressive, digressive or linear behavior of a shock/fork I think you want to look at damping force over velocity.

I can dig one up when I get home, I do not have one online that I can post at the current time.

The problem with force vs. velocity is that you lose all ability to see what is happening at low damper velocities, because the force values are so low that everything blends together on the graph on the slow end. For example, a 25% change in damping force at 10 in/sec might end up only being a couple pixels. The coefficient curve makes it much easier to see what happens at different damper velocities, and makes it really obvious if it is linear, digress, or progressive. If the coefficient curve is straight and horizontal (sort of like the TE610 curve above), the damping is pretty linear. A curve that tilts "down" (like most BV curves) is digressive, and a curve that tilts up (most MV curves) is progressive.

I finally picked up a set of E forks, so I'll be able to experiment too. I would like to see a 2 stage stack, 3 seems overall complicated (at least from what I've read, but there are many ways to achieve the same goals) especially in terms of understanding the stacks function.

You could certainly build a 2-stage stack that would function better than stock, but I messed around with it for a while and I couldn't figure out how to build a 2-stage stack without having it be quite digressive. That is why I went to the 3-stage. I think a 2-stage would work really well with a midvalve.

I wonder if there would be any benefit to opening up the bleed orifice in the piston to bring down that initial spike in damping.

I've considered opening up the adjuster bleed, adding a bleed port, and using a bleeder shim. All of these options can get you into trouble real quick, though. A 1.5mm bleed hole might work, and could be plugged with epoxy if it didn't work out. I didn't look at the adjuster circuit much, but that may be drill-able too.

I've come up with some other changes to the first stage that help a bit more with the initial spike. Right now I am using a 15mm crossover, going to a 12mm crossover seems like it'll help with that.

I can't wait for more feedback from other members as well. Here's a piece from a resident guru I found early when searching for info here:

for what type of riding? most situations need the following-

forks need more low speed compression dampening,the oil level set at 100mm,10wt fluid.

the shock needs more low speed rebound,reduced high speed compression.5wt fluid.

What's interesting is that the restackor curves don't really agree with this, and neither does my (limited) experience. The biggest problem I had with fork compression was bottoming and blowing through the stroke, which is mid-high speed compression. I believe the reason these forks don't feel as "good" as the set of forks on (for example) my WR300 is the lack of a proper midvalve; a midvalve adds mid and high speed damping, and is very progressive, sort of the opposite of adding low speed damping as per Eddie. 10wt fluid is pretty thick too, most of the stuff I've read from suspension tuners seems to indicate that they like using a lighter fluid and adjusting valving to suit.

On the shock side I have not spent as much time, but it seems like it needs more high speed rebound (to help with kicking)...

I don't want to doubt Eddie's experience, but this is my perception, and so far it seems to be working.

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I took some measurements of the BV ('03 DRZ400S) and wanted to confirm the inputs you are using (shim stack is the same as you posted).

Compression-Side

  • Drod - 12 mm
  • Dvalve - 28 mm
  • wseat - 0.5 mm
  • Rport - 5.75 mm
  • Dport - 5 mm
  • Wport - 5 mm
  • Nport - 4
  • Dbleed - 2.15 mm
  • Dleak - 0 (no leak ports within the piston)
  • Dthrt - 3.89 mm
  • Nthrt - 4

Mine are similar. What I have in my sheet is:

  • Drod - 12 mm
  • Dvalve - 28 mm
  • wseat - 1.2 mm
  • Rport - 5.7 mm
  • Dport - 4.8 mm
  • Wport - 4.6 mm
  • Nport - 4
  • Dbleed - 2.0 mm
  • Dleak - 0 (no leak ports within the piston)
  • Dthrt - 4.2 mm
  • Nthrt - 4

So, pretty similar to your numbers. My Dbleed might not be perfect, and that's pretty sensitive, so you ought to remeasure that. 2.0mm is the smallest of all of my bikes (my WR is like 2.5, TE is nearly 3).

I will note that the base valve numbers (and appearance) is pretty darn good; the ports are big, the flow paths look good, etc. I see no reason why you'd need modifications or an aftermarket valve on these forks (except for the aforementioned bleed stuff). Sorry, RaceTech guys!

Are you going to experiment with a proper midvalve setup?

I would definitely like to. I think that it's not necessary for casual trail use, but for more aggressive use, racing, MX, desert, etc I think it would make a significant difference.

The problem is that I live on the east coast (PA) but my DRZ lives in Colorado for the couple times a year I go out to ride it. I don't race it out there, just trail ride and dual sport, and it's a huge pain to ship my forks back and forth. I think that the current setup is "good enough" for what I use it for, so I may not bother.

If there is someone on here that wants to experiment with a midvalve, I'd be really interested to see how it works, so I'd be happy to install one for them for the cost of parts (probably around $50). I also have a cool idea about machining the stock midvalve checkplate sleeve to allow the addition of midvalve shims without needing to buy a sleeve, washer, spring, and all that other stuff. Again, if somebody wants to volunteer their forks, I'd love to try it and document it with pictures and sketches so I can post them up here for other guys to try.

I have already run through the numbers and everything in restackor, so I have a good sense for what the midvalve stack should be, etc. Anyone who's interested, let me know...

Edited by Kyle Tarry

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Mine are similar. What I have in my sheet is:

  • Drod - 12 mm
  • Dvalve - 28 mm
  • wseat - 1.2 mm
  • Rport - 5.7 mm
  • Dport - 4.8 mm
  • Wport - 4.6 mm
  • Nport - 4
  • Dbleed - 2.0 mm
  • Dleak - 0 (no leak ports within the piston)
  • Dthrt - 4.2 mm
  • Nthrt - 4

When I pulled the piston the first thing I did was surface/lap both piston faces on plate glass and 400 wet/dry paper. Both pistons had a good amount of irregularities. By lapping not only is the seal going to be better between the shims and piston it also makes it easier to measure since you now have a distinct gray (lapped area) vs. the gunmetal finish of the piston. It’s something I picked up watching the RT fork rebuild videos. Wseat is definitely closer to 0.5 - 0.75 mm (measuring the newly lapped edge around the piston). I used a steel rule because the lip/seat isn't tall enough to grab with calipers and by eye is wasn't working for me.

As far as the bleed orifice that was difficult as well. I had a jeweler’s screwdriver with a diameter of 2 mm that was a loose fit within the orifice. I found a screw that fit tighter and my measurement was 2.15 mm.

Also those plots are with the comp clickers at what setting (middle, open, closed)?

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Cool idea on the lapping. I will change my Wseat down to 0.75 and see if it changes the plots significantly.

I measured the bleed orfice the same way (different size drill bits in this case). I think 2.0-2.1 is the right number...

My plots are all with the clickers set in the middle (8/16, I think). FYI, one way to help with the initial harshness is to run the clickers close to wide open to improve the bleed. This works, but then you lose the ability to further adjust things from there, which is a bummer. On my bike I run them around 12/16 or so, which helps...

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Yeah, I have seen that thread, and that info was helpful to me. I don't fully agree with the shim stacks he came up with (too stiff for my riding), but nonetheless I think it's great to see the info out there. If he's still around, it would be cool to get some of his feedback in here.

I think that adding a midvalve is a logical idea, but it's also a much bigger project. For many DRZ owners, tracking down all of the midvalve parts and doing the installation may feel like too much; I felt that my improved basevalve stack would be a feasible option that many guys who are unsatisfied with their suspension could try.

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Okay went back and measured with a rivet that fit just right Dbleed 2.19 mm (0.08625-0.0865 in).

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Okay went back and measured with a rivet that fit just right Dbleed 2.19 mm (0.08625-0.0865 in).

It is amazing how much difference a little bit of bleed makes. Changing the bleed from 2.0mm (the number I had) to 2.2mm (the correct number) makes the initial damping spike, with my 3-stage revalve shown above, drop from 0.8 to 0.6 on the damping coefficient. It doesn't have much impact elsewhere, but it changes the initial quite a bit.

I think that this is a good thing, because that initial spike was worrisome to me.

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It is amazing how much difference a little bit of bleed makes. Changing the bleed from 2.0mm (the number I had) to 2.2mm (the correct number) makes the initial damping spike, with my 3-stage revalve shown above, drop from 0.8 to 0.6 on the damping coefficient. It doesn't have much impact elsewhere, but it changes the initial quite a bit.

I think that this is a good thing, because that initial spike was worrisome to me.

So I started playing with restackor... it seems like that initial spike in damping (0-10 ips) is mostly controlled by bleed (clicker, leak or bleed shim) and shim changes have no real significant impact. I guess you could run the clickers further out, but stiffen the stack to compensate. I also ran through our measurements and the port lengths (d.port and w.port) have a large affect on hi-speed damping on the order of 20% (50-200 ips).

Here are my settings and the reason I used 2.83 wt oil is that it corresponds to 15.9 cSt @ 40C (according to the user manual) which is what 5wt maxima fork fluid is:

drz400 settings.png

In your stack, is the last shim (against the valve body, not the piston) a 12 mm as per your listed stack or do you still have the 11.4 x 0.4 (2x) shims there like the factory stack?

When I first ran the factory stack I noticed the very last shims (9, 12, 11.4 mm near the clamp) were bending, which isn't possible since they rest against the valve body. The last shim that should bend is the 12 mm in the factory stack. So what I did was add a very last "shim" which simulates the end of the valve body that the shims rest against (14.9 x 7.3 mm).

So here is the factory stack vs. your 3-stage:

drz400 stock vs. kt 3stg.png

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I am still running the two 11.5mm OD shims under my "functional" stack. In Restackor, I have the end shim in as a 11 x 1mm, just to fake some stiffness to make it behave correctly. Putting the base in the way you did with a thick shim in place of the valve body is a totally legitimate way to do it too.

Your plots agree pretty well with my results. My initial spike is a bit higher because of the smaller bleed I was using, but otherwise it looks very siimilar!

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I am still running the two 11.5mm OD shims under my "functional" stack. In Restackor, I have the end shim in as a 11 x 1mm, just to fake some stiffness to make it behave correctly. Putting the base in the way you did with a thick shim in place of the valve body is a totally legitimate way to do it too.

Your plots agree pretty well with my results. My initial spike is a bit higher because of the smaller bleed I was using, but otherwise it looks very siimilar!

Okay cool, also fluid weight has a big impact on that spike (5 vs. 2.83 wt). According to the manual, he based SAEwt on the weights of silkolene fluid (2.5, 5, 7.5 & 10 wt). So it'd be good to take a look at peterverdone's site to listed cSt of different weights.

Now how far out should we be looking, is 200 inches per second a realistic maximum velocity that a woods/enduro rider can expect to see?

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Okay cool, also fluid weight has a big impact on that spike (5 vs. 2.83 wt). According to the manual, he based SAEwt on the weights of silkolene fluid (2.5, 5, 7.5 & 10 wt). So it'd be good to take a look at peterverdone's site to listed cSt of different weights.

Now how far out should we be looking, is 200 inches per second a realistic maximum velocity that a woods/enduro rider can expect to see?

Good question :) I think I've probably hit 3-4" obstacles at close to 50+ mph. Not often, but it has happened. After a quick look at the graphs over at shimrestackor.com, I wouldn't immediately exclude 300-400 in/sec as a realistic maximum.

4-dirt-21f.png

http://www.shimrestackor.com/Code/User_Manual/Sections/Suspension_Velocity/suspension-velocity.htm

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Okay cool, also fluid weight has a big impact on that spike (5 vs. 2.83 wt). According to the manual, he based SAEwt on the weights of silkolene fluid (2.5, 5, 7.5 & 10 wt). So it'd be good to take a look at peterverdone's site to listed cSt of different weights.

I don't worry about this too much. Not that it isn't relevant (it is), but I figure that all of the graphs are relative to each other, so I put in the weight I am going to use and try not to vary it.

Now how far out should we be looking, is 200 inches per second a realistic maximum velocity that a woods/enduro rider can expect to see?

I agree with Anthon, 300 in/sec or so it probably a good number. You can always come up with a situation where you might see more, but they're rare.

That being said, these curves all get really flat at higher speeds, so I don't think it makes too big a difference.

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I don't worry about this too much. Not that it isn't relevant (it is), but I figure that all of the graphs are relative to each other, so I put in the weight I am going to use and try not to vary it.

I agree in that there are so many variables that have profound impact on the results that the graphs need to be looked at as a "change" from baseline (relative). I just want the inputs to be as close to actuality as possible.

I agree with Anthon, 300 in/sec or so it probably a good number. You can always come up with a situation where you might see more, but they're rare.

That being said, these curves all get really flat at higher speeds, so I don't think it makes too big a difference.

I believe that's due to the port size of the piston, if you input enough force on the shim stack... you'll get to a point where the shims no longer deflect anymore and the flow its changing much. The restriction to flow now is the port size and not the shims (whether there's 1 or 20 shims).

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Good question :) I think I've probably hit 3-4" obstacles at close to 50+ mph. Not often, but it has happened. After a quick look at the graphs over at shimrestackor.com, I wouldn't immediately exclude 300-400 in/sec as a realistic maximum.

4-dirt-21f.png

http://www.shimresta...on-velocity.htm

His calculations are for square-edged stuff... so that's pretty gnarly hitting 3-4" obstacles at 50mph+ (like a small curb).

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