DRZ400 suspension revalving

[bmwpowere36m3]

Hey guys, I found this forum when I was searching for suspension valving info and found a member, Tyle Tarry who had some info. He said he was willing to share some info, so I'm creating this thread.

I recently acquired a 2000 DRZ400S and its in need of some suspension work. I ride in the Northeast, mostly single track (2-3 gear stuff) that's rocky (softball size) and rooty. I weight 180 lbs without gear. With some small jumps and whoops thrown in. Overall I'd say the bike is fairly soft and on rocky bits when I have some speed the bike doesn't instill confidence. Also when hitting small jumps and ledges the front end drops and the rear kicks up. Going over whoops is a nightmare... thinking I'll get thrown over the bars.

I'm in the process of swapping over to newer DRZ suspension components because the old shock lacked rebound and HS comp adjustments and the forks are damper rod style.

I just got a DRZ400E shock and I'm still waiting for a set of forks. At the same time I’ll be picking up some 5.7 kg/mm rear springs and I'm not sure as too the forks. Many seem to use 0.46-0.48 kg/mm at my weight on the DRZ sub-forum.

I figured I'd ask if there was any revalving advice while I have the shock apart for service.

2003 DRZ400E Stock Shock Shim Stack

• 12 x 1.25 NUT
• 25 x 3 PLATE
• 25 x 0.6
• REBOUND
  • 24 x 0.30
  • 26 x 0.30
  • 28 x 0.30
  • 30 x 0.30
  • 32 x 0.30
  • 34 x 0.25
  • 36 x 0.25
  • 38 x 0.25
  • 40 x 0.20
  • 25 x 0.10
  • 40 x 0.20 (6x)
• PISTON
• COMPRESSION
  • 44 x 0.20 (4x)
  • 44 x 0.15 (3x)
  • 34 x 0.15
  • 26 x 0.10
  • 42 x 0.20
  • 40 x 0.20
  • 38 x 0.20
  • 36 x 0.20
  • 34 x 0.20
  • 32 x 0.20
  • 30 x 0.20
  • 28 x 0.20
  • 26 x 0.20
  • 24 x 0.20
  • 22 x 0.20

• 40 x 0.30 (2x)
• 41 x 4 PLATE
• 18 x 0.60 SPACER

Any advice?

 

[Kyle Tarry]

In addition to my two Huskies, I have a 2000 DRZ-400K (kick-start only) that lives out in CO for the several times I year I go out there to ride. Since it's not my primary bike it doesn't need to be perfect, but it's really bad, bad enough that I wanted to make some improvements. Since it's the K/E model, it has the cartridge forks. My opinion is that the forks are way worse than the shock, so that's where I started working.

The bike is ridden in a pretty wide variety of terrain; rocky CO singletrack, Moab slickrock, fast dirt roads, baja whoops... In stock form, my opinion is that it's pretty soft everywhere, although maybe a tad harsh on some low speed hits. In whoops it's dangerous, I pissed blood for a week after it tossed me in baja pre-running the 1000 last year. I'm just stating to work on it, and I think it will take a couple iterations to get it right, but maybe we can work together and make some progress. For the record I weigh about 170, wear a lot of gear (camelbak, tools, big tank), and am an aggressive C-level rider.

For starters, I went from the stock 0.44 fork springs to 0.48. I hoped this would firm up the front end, but to be honest it didn't seem to make that much of a difference. I think it's more a function of damping.

Stock fork shim stack:
24 0.1 (6X)
15 0.1
24 0.1
22 0.1
20 0.1
18 0.1
16 0.1
14 0.15
12 0.2
9 0.2

Midvalve is a check plate, so all of the damping is on the base valve.

As a point of comparison, this is pretty similar to the stock stack in my WR300, except the WR has 0.11mm thick shims (~30% stiffer), has an 11mm clamp shim instead of a 9, and has damping on the midvalve, which adds a TON of high speed damping (but not much at low speed). The DRZ is also 50 pounds heavier. Stock KTM 300 2-strokes are similar to the WR (and thus the DRZ). So, I'd argue that the DRZ is pretty soft in stock form, given that the BV is comparable to (if not softer than) a 220-lb 2-stroke WITH midvalve damping.

In some ways, I think a better point of comparison is my TE610. Similar size bike to my DRZ, and the TE also has a checkplate on the midvalve in stock form (WTF, Husky/Marzocchi?). The stock TE610 stack looks like this:

23 0.15 (3X)
12 0.10
21 0.15
19 0.15
17 0.15
15 0.15
13 0.20
11 0.20

Doesn't look like much, but when you consider that it's all 0.15mm shims (~3x stiffer than 0.10mm), it's probably something like roughly 2X as stiff as the stock DRZ stuff. The TE doesn't feel perfect, but it's a heck of a lot better than a stock DRZ, it actually feels like a real bike.

I am going to work on my forks in a couple of phases. Phase 1 is coming up with a new BV shim stack, leaving the checkplate in the midvalve, and seeing how the bike rides. This was easy, doesn't require tracking down a bunch of parts for the midvalve conversion, and would also be easy for other guys to replicate.

Phase 2, if needed, will be installing a shim stack on the midvalve, modifying the base valve to match, and having a "real" offroad fork on the bike. I think I will end up doing this but I haven't ridden phase 1 yet, so time will tell.

I have a bunch of interesting data from Shim ReStackor that I will share when I get time to make a couple graphs into pictures, hopefully later this evening. Stay tuned...

 

[Kyle Tarry]

Ok, have a little bit of time, so some more info.

First, I put the stock DRZ valving into ReStackor along with a couple other common bikes. The WR and TE should be fairly accurate, as I measured those myself; the stack info for the EXC, I just got off the web.

So right away we can see a few things. The DRZ starts off pretty stiff (I think this is because the bleed orifice is pretty small, 2mm dia), and then it quickly drops down to about the level or the WR and the EXC basevalves. I added another line showing the WR total damping (base + mid), you can see how much the mid adds, especially up top. You can also compare the DRZ to the TE, both bikes being about the same weight and neither having a midvalve. The DRZ has less than half the compression damping that the TE has, after they both settle out.

So, for phase 1, I set out to build a BV stack that tries to "compensate" for the lack of a bunch of MV damping. I also wanted to try to take out a little bit of the initial spike at low speeds. I removed the 9mm clamp shim (stiffen the whole stack), moved the crossover up quite a few shims, added a second crossover using one of the shims that was in the taper, and added a couple 24x0.15 shims to form a stiff 3rd stage:

240.1 (3X)
150.1
240.1 (3X)
220.1
180.1
140.15
240.15 (3X)
220.1
200.1
180.1
160.1
120.2

This is the result:

Now, we've slightly reduced the initial spike in damping, we have about 25% more damping at mid speeds, and about 50% more damping at high speeds. The overall damping is a lot closer to the TE610, and it isn't as digressive.

This is the stack that is in my bike now. I will ride the bike in 2 weeks and give some feedback.

In the future I'd like to try to reduce the initial spike a little bit more; maybe I will play around with a bleed shim?

Here is a stack using only the stock shims that I think would be an improvement over stock:

240.1
240.1
240.1
150.1
240.1
240.1
240.1
240.1
220.1
200.1
180.1
160.1
140.15
120.2

To get here, you just pull the 9mm clamp shim, and move the crossover up 3 places. Removing the tiny clamp stiffens up the whole stack, and the crossover might help with the low-low speed. This isn't as significant a change as my 3-stage stack, it's about 15% more damping in the mid and 25% more high. I would like to try this, and it might work well for a casual rider, but I don't think it's enough for me.

That's all the time I have for now; will update this later.

P.S. On my way home today, I was thinking about the midvalve, and I think I have a way to add a shim stack without needing to source all the sleeve, washer, spring, etc parts from another bike or a supplier. I think I can turn down the end of the sleeve that is in there and put a shim stack right there, using the stock spring, etc. Hopefully when I get back home in a few weeks I can mess around with this idea. It would be neat if we could come up with a simple "kit" with the modified sleeve to allow people to add a tunable midvalve to their DRZ for cheap/easy...

 

[bmwpowere36m3]

Very interesting any shock stuff?

A member (MarekB) on another site, put together a midvalve with parts sourced from SDI. He weighs 155 lbs rides a mix of sandy woods (mostly) & MX stuff.

BV:

• 24 x 0.10 (11x)
• 22 x 0.10
• 20 x 0.10
• 18 x 0.10
• 16 x 0.10
• 14 x 0.15
• 12 x 0.20
• 11.5 x 0.40

MV:
8mm ID

• 24 x 0.1 (4x)
• 22 x 0.1
• 20 x 0.1
• 18 x 0.1
• 16 x 0.1
• 14 x 0.1
• 12 x 0.1
• 11 x 0.3 (2x)
• 17 x 0.3 (2x)

6mm id

• 10 x 0.2
• 11 x 0.3
• spring
• cup washer

Collar 5.3mm x 6 ID x 8 OD

Float is about 0.3 - 0.4mm

His comments,

"I'm a bit less happy with fork valving - it works well on big hits but at the same time I have a lots of reflection from roots, stones etc. when riding fast. For woods I'd increase float to 0.5 mm and probably stiffen a base valve a bit also adding crossover shim. Fork valving needs some further work, especially for harder terrain (I ride mostly sand)."

 

[Coffee]

I've been staring at your graphs for a while now, is the TE610 a good suspension as per the graph? Soaks up the low speed quickly, but gets more dampening at higher speeds?

Up until now I've been thinking in terms of stroke, little dampening early in the stroke (plush), more dampening the more compress the forks (or shock) was - but I am clueless about suspensions.

 

[Kyle Tarry]

I've been staring at your graphs for a while now, is the TE610 a good suspension as per the graph? Soaks up the low speed quickly, but gets more dampening at higher speeds?

TE610 is "okay." Good and bad are so relative and subjective that it's hard to answer. I can say that the TE is WAY better than a stock DRZ, or other "dual sport" type bikes. It's "worse", arguably, than something like a WR or a new TC or TXC or anything like that.

Note the the TE is pretty linear, once it overcomes the bleed effects at very very low speed. The WR, as you can see, is much more progressive. All other "race bike" type bikes (WR, CR, TC, TXC, KXF, CRF, etc) will be progressive on some level, probably.

Up until now I've been thinking in terms of stroke, little dampening early in the stroke (plush), more dampening the more compress the forks (or shock) was - but I am clueless about suspensions.

Damping (don't need the extra "en" ) is not position sensitive on 99% of forks, it is only speed sensitive.

 

[Kyle Tarry]

Very interesting any shock stuff?

A member (MarekB) on another site, put together a midvalve with parts sourced from SDI. He weighs 155 lbs rides a mix of sandy woods (mostly) & MX stuff.
...
"I'm a bit less happy with fork valving - it works well on big hits but at the same time I have a lots of reflection from roots, stones etc. when riding fast. For woods I'd increase float to 0.5 mm and probably stiffen a base valve a bit also adding crossover shim. Fork valving needs some further work, especially for harder terrain (I ride mostly sand)."

My comments just from looking at the stack would be similar to his. I can't say for sure, but to me both the base and the mid look a little bit "stiff" for rocky/woods/trails riding. I would think you could run less face shims (maybe 6-8, I dunno), run a crossover after the first 2-4 face shims, and then on the MV I would probably try 0.5-0.8mm float and maybe a bit softer on the stack.

I bet his setup works well for something like a NJ hare scramble, or a sandy MX track without any huge hits.

My uneducated opinion would be that when trying to set a DRZ up for rocks, creep up on the stiffness. Being too soft means you're still way better than stock and bike isn't beating you up in the meantime; if you go too stiff, it'll be crappy to ride and you'll probably want to go back in there right away to make changes.

I am waiting on MX tech to tell me what parts I need to add midvalve damping, but I am thinking I will give up on them and just machine the stock piece instead...

 

[bmwpowere36m3]

My comments just from looking at the stack would be similar to his. I can't say for sure, but to me both the base and the mid look a little bit "stiff" for rocky/woods/trails riding. I would think you could run less face shims (maybe 6-8, I dunno), run a crossover after the first 2-4 face shims, and then on the MV I would probably try 0.5-0.8mm float and maybe a bit softer on the stack.

I bet his setup works well for something like a NJ hare scramble, or a sandy MX track without any huge hits.

My uneducated opinion would be that when trying to set a DRZ up for rocks, creep up on the stiffness. Being too soft means you're still way better than stock and bike isn't beating you up in the meantime; if you go too stiff, it'll be crappy to ride and you'll probably want to go back in there right away to make changes.

I am waiting on MX tech to tell me what parts I need to add midvalve damping, but I am thinking I will give up on them and just machine the stock piece instead...

Yea I wasn't sure because he mentioned increasing the float which made sense, but then adding even more face shims to the BV? Seems like all the midvalve parts can be purchased through SDI as listed in his stack.

Have you made any shock changes or just the forks?

 

[Kyle Tarry]

Yea I wasn't sure because he mentioned increasing the float which made sense, but then adding even more face shims to the BV?

Yeah. I threw the stacks into ReStackor out of curiosity, and his BV stack looks WAY stiff for the kind of riding I (we?) do (rocky singletrack, etc). I think his MV is ok, maybe one less face shim, add a bit of float, but nothing major. On the other hand, I think his BV should be quite a bit softer, and with a crossover, to get compliance for trail crap. I would probably try something like 6-8X 24x0.1 face shims with a 14-15mm crossover after 3 of them, and then use the rest of his stack. Actually, that would be pretty close to the stock stack, except with a crossover and maybe another couple 24s.

Seems like all the midvalve parts can be purchased through SDI as listed in his stack.

Yeah, and MX-Tech was able to get them for me too.

Have you made any shock changes or just the forks?

Only the fork, I'm afraid! Sorry! My perception is that the shock is ok but not great, while the forks are dangerously terrible. I may look at the shock in the next round.

 

[bmwpowere36m3]

Yeah. I threw the stacks into ReStackor out of curiosity, and his BV stack looks WAY stiff for the kind of riding I (we?) do (rocky singletrack, etc). I think his MV is ok, maybe one less face shim, add a bit of float, but nothing major. On the other hand, I think his BV should be quite a bit softer, and with a crossover, to get compliance for trail crap. I would probably try something like 6-8X 24x0.1 face shims with a 14-15mm crossover after 3 of them, and then use the rest of his stack. Actually, that would be pretty close to the stock stack, except with a crossover and maybe another couple 24s.

The stock fork BV being:

• 24 x 0.1 (6x)
• 15 x 0.1
• 24 x 0.1
• 22 x 0.1
• 20 x 0.1
• 18 x 0.1
• 16 x 0.1
• 14 x 0.15
• 12 x 0.2
• 9 x 0.2
• 11.5 x 0.4

Essentially his stack has more face shims, no crossover and a larger clamp (11.5 vs. 9). I guess he used what was originally the baseplate (11.5 x 0.4) as the last shim, which now would be the clamp. I don't have the experience to say how much stiffer the BV would be.
I guess what's the difference between having a crossover down in the BV after a few face shims vs. more float at the MV?

 

[Kyle Tarry]

I put his bv stack into restackor and it was quite a bit stiffer than stock. 11 vs 6 face shims is already quite a bit stiffer, plus the larger clamp. I don't remember exactly but I think it was nearly twice as stiff on initial opening. My opinion is that, for woods work, the drz needs a fairly early crossover, like after 3-4 face shims, to let the oil flow at low pressures. With his stiff stack and no crossover, the entire stack has to move to let oil by initially.

For bv vs mv, the bv damping dominates at low speeds. Float effects when and how much the mv comes into play at mid and high speeds, but the bv is the big player initially, at least on an enduro system with moderate float. Graphs make this easy to understand but I am on the road right now.

FYI, this is all based primarily on playing with restackor and reading, I am far from an experienced tuner.

 

[bmwpowere36m3]

Do you know how a typical shock absorber equipped with an external reservoir (not fork) is modeled in shim restackor? The piston in the main body is a mid-valve correct? So the compression adjuster would be the base-valve? When modeling, do most omit the base-valve and just look at the mid-valve? Thus any results or configuration changes would only show the relative damping of the mid-valve... but not accurate total damping.

I only got the throat diameter of the port for the comp needle. I'd have to fully disassemble the adjuster to get the shims, spring rate, piston, etc... How can I calculate the combined mid-valve and comp. adjuster damping force and damping coefficient?

Also when modeling the compression damping, do you take into account bleed through the rebound needle (though it would vary with its position)?

2003 DRZ400E (Showa Shock)

Compression-Side

• Drod - 16 mm
• Dvalve - 50 mm
• Wseat - 0.75 mm
• Rport - 10.25 mm
• Dport - 11 mm
• Wport - 14 mm
• Nport - 4
• Dbleed - 2 mm (comp adjuster needle throat)
• Dleak - 0
• Dthrt - 8.5 mm
• Nthrt - 4

Rebound-Side

• Drod - 16 mm
• Dvalve - 50 mm
• Wseat - 0.75 mm
• Rport - 10.25 mm
• Dport - 9 mm
• Wport - 11 mm
• Nport - 4
• Dbleed - 3.5 mm
• Dleak - 0
• Dthrt - 5.92 mm
• Nthrt - 4

 

[Radbuster]

Hi, I'm no expert but I managed to get my wp48 open chamers to work well in similar conditions. Based on that and your input I'd suggest only 2 face shims before the crossover but go up to maybe 5-9 24's after that. The float, my impression, mainly affects the ride height of the fork. Less = longer fork better for soaking up stuff but worse turning.
Your idea of a bleed shim could also be useful.
Try checking your sag front and rear per Vinduros guidelines re the spring rates.
Interesting! Pls keep us posted.
Good luck.

 

[Kyle Tarry]

Do you know how a typical shock absorber equipped with an external reservoir (not fork) is modeled in shim restackor? The piston in the main body is a mid-valve correct? So the compression adjuster would be the base-valve? When modeling, do most omit the base-valve and just look at the mid-valve? Thus any results or configuration changes would only show the relative damping of the mid-valve... but not accurate total damping.

I would think that the shock would be modeled as a midvalve. I'm not so sure about the compression adjuster, maybe one of the other suspension guys (Sparked, Picklito, Motorhead) can chime in here?

I sort of look at it as, if you change the shim stacks, you're only going to effect the moving piston ("midvalve") anyway, so modeling that is probably sufficient. That's probably more crude than it could be though, because you can't really factor in the clicker settings, etc.

Also when modeling the compression damping, do you take into account bleed through the rebound needle (though it would vary with its position)?

Yeah. I just put the same adjuster click numbers on the comp side of the MV as I use on the rebound side. This is how I do fork midvalves, not shocks (haven't done any shock stuff yet), but it should still apply.

I am headed out to CO this holiday weekend to ride my DRZ, so I will shortly be able to report back on how the fork performs...

 

[Kyle Tarry]

I rode my DRZ out in Colorado this past holiday weekend (Thurs, Fri, Sat, Sun). In general, I am quite pleased with the forks. They are certainly not perfect, but they are WAY better than stock, and good enough to be able to ride the bike like a real motorcycle.

We rode a mixed bag of terrain: fire roads, dual track, loose rocky climbs, 1st gear technical rocky climbs, rock gardens, etc. In the rocky stuff, the bike does fairly well, and the front end deflection isn't bad, probably better than stock, I would like to try to improve this a little bit. On faster stuff the bike feels good. Bottoming was previously a huge problem, and while we didn't ride any big hits, I jumped LOTS of 3rd-4th gear water bars 1-3 feet tall and it never bottomed, although it did feel like it was using up most of the travel.

All in all, I think that the 3-stage stack I came up with would be a really good option for somebody who doesn't want to spend a lot of money, doesn't want to dig into the midvalve, and wants to be able to ride their DRZ like a real dirt bike.

On the rear, I found that I had to dial the compression about 75% of the way out, and the rebound probably only 30% of the way out, to have compliance on rocks while keeping the rear from kicking up on rebound. If I was going to revalve the shock (I may not bother, we'll see what time allows), I would try to add some high speed rebound damping (maybe move a couple of shims to the other side of the crossover) and take out a bit of low speed compression?