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Proper suspension lowering/valving...DIY or Outsource?

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I am becoming prepped to rebuild my 04 S suspension. (yes the rear linkages have all been greased and cleaned regularly and will come out easily!)

At first it was "just seals, and oil"

Then it was "while I'm in there...gold valves..."

Then it became "I got a low seat and a 28" inseam...maybe lower it properly...while I'm in there"

And now it is sort of like "shit I am buying so many parts I might as well cough up the bit more $ to have someone experienced build it for me"

 

But that is just not me.  I been a bicycle mechanic for 21 years, and always have a slew of projects that I'm learning on!  I been in a lot of complicated suspensions on MTB's that cost as much or more than a DRZ!!  But they are usually air sprung, and small.

 

IMO...I have very good wrench skills and intuition.  Fair to good understanding of shims, and suspension concepts and workings. And low experience, but high confidence! (almost as dangerous as a motorbike with shitty suspension)  

 

Thing is in gathering my intel.  No one wants to spill the beans about proper lowering with spacers internally. (which becomes the reason you send it to Race Tech)

The questions I might like to find answers to:

 

1--Because the stroke length becomes shorter, if the spring is not shorter than it will act as if it is a "firmer" spring than its printed spec.  So how would one compensate or calculate for this?  Same rate spring for my weight but just 1" shorter??  (I understand the rear is on a leverage ratio, and has adjustable preload, so may be more forgiving...err adjustable)

2--I have viewed rear shock travel spacers on Race Techs site, but they do a good job of hiding whatever spacer is used in the fork.  Anyone know what to get and where to get that?  Or is it going to be a make one yourself scenario?

3--How many specialty tools will I need to buy to do the rear shock, not including Nitro charge setup, I would finish the job off by paying a shop to nitro charge it.

4--Should I just send it out.  Seems like once you throw internal spacing into the mix, it becomes "black magic"  Like I can do it, but I can't let you know the "secret"--or call us for info and send it in.

5--I know there are things I am missing, misinformed, and not yet aware of.  I am not insulted by people telling me what I don't know, and can't do.  Fire away please

 

I am about 180 lbs, will sometimes carry camping/touring gear >50 lbs , and think it would be great if my bike were 1" lower.  I am cool with losing the inch of ground clearance.  And as you can tell despise the notion of lowering links and riser blocks!!  I am riding it fine as is, and deal with the DRZ's tallness and my lack thereof...but since I am gonna be tearing it apart.  Being lower would help, but it needs to be done right, otherwise I'll continue on my toes & 1/2 ass it!

 

Anyone been down this road or have experience and know-how doing this?   I'd be really grateful to hear about it!!

Edited by kevvyd

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1--Because the stroke length becomes shorter, if the spring is not shorter than it will act as if it is a "firmer" spring than its printed spec.  So how would one compensate or calculate for this?  Same rate spring for my weight but just 1" shorter??  (I understand the rear is on a leverage ratio, and has adjustable preload, so may be more forgiving...err adjustable)

 

2--I have viewed rear shock travel spacers on Race Techs site, but they do a good job of hiding whatever spacer is used in the fork.  Anyone know what to get and where to get that?  Or is it going to be a make one yourself scenario?

 

3--How many specialty tools will I need to buy to do the rear shock, not including Nitro charge setup, I would finish the job off by paying a shop to nitro charge it.

 

4--Should I just send it out.  Seems like once you throw internal spacing into the mix, it becomes "black magic"  Like I can do it, but I can't let you know the "secret"--or call us for info and send it in.

 

1) Just to be sure: The spring rate does not change! A more compressed spring is not stiffer. It does store more and more energy, but it's not stiffer. You might want a stiffer spring to pair with the shorter travel, but not necessarily. Depends :) The spring rate could be ballpark calculated. Let's say you have a spring with spring rate 50 and 10 inches of travel and you like how it feels - plush but taut ride that uses up your suspension travel on big hits but only bottoms out very rarely if at all. You want to take 1 inch travel away and end up with 9 inches. Then I imagine you would want a 55.5 spring rate? IOW the original spring rate divided by 9 and multiplied by 10? I think that would be how it work? You would need a new spring, or to cut the old spring - cutting springs makes them stiffer :) But you don't automatically NEED a stiffer spring if you reduce the travel.

 

2) I believe the spacer is a very simple PVC pipe equal to the length you want to reduce travel by. Same dimensions as the fork spring? I'm not 100% clear on where you put the spacer, but looking around on writeups it seems to be at the lower end of the fork, near the compression valve? Tutorials on this mention that you change the length of the top-out spring but the DR_Z forks don't have a topout spring. I belive it just makes the process simpler? But I'm not sure?

 

3) There are some VERY good fork and shock rebuild videos on Youtube! Check out a few of those and you'll get a pretty good idea of the tools required!

 

4) Depends on what would be the most fun for you. If you like to tinker and wrench, I can recommend trying the front fork revalve as something of a challenge but still a fun garage job. I think I would recommend sending it out to most people :) But I can't be sure.

Edited by Anthon Berg

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1) Just to be sure: The spring rate does not change! A more compressed spring is not stiffer. It does store more and more energy, but it's not stiffer. You might want a stiffer spring to pair with the shorter travel, but not necessarily. Depends :) The spring rate could be ballpark calculated. Let's say you have a spring with spring rate 50 and 10 inches of travel and you like how it feels - plush but taut ride that uses up your suspension travel on big hits but only bottoms out very rarely if at all. You want to take 1 inch travel away and end up with 9 inches. Then I imagine you would want a 55.5 spring rate? IOW the original spring rate divided by 9 and multiplied by 10? I think that would be how it work? You would need a new spring, or to cut the old spring - cutting springs makes them stiffer :) But you don't automatically NEED a stiffer spring if you reduce the travel.

 

2) I believe the spacer is a very simple PVC pipe equal to the length you want to reduce travel by. Same dimensions as the fork spring? I'm not 100% clear on where you put the spacer, but looking around on writeups it seems to be at the lower end of the fork, near the compression valve? Tutorials on this mention that you change the length of the top-out spring but the DR_Z forks don't have a topout spring. I belive it just makes the process simpler? But I'm not sure?

 

3) There are some VERY good fork and shock rebuild videos on Youtube! Check out a few of those and you'll get a pretty good idea of the tools required!

 

4) Depends on what would be the most fun for you. If you like to tinker and wrench, I can recommend trying the front fork revalve as something of a challenge but still a fun garage job. I think I would recommend sending it out to most people :) But I can't be sure.

 

Anthon,  Thanks for the feedback.

 

1)  I understand and agree with what you say here.  Stiffer spring rate for shorter travel is what you want--agreed?

     But if the spring is not shorter wouldn't you get coil bind before actual bottom of travel?

 

2)  I too know the "spacer" would go at the bottom near the compression valve.  I too am looking at things to figure out exactly where such that it will stay put.  And I agree that the lack of top out spring could only make it less complicated. (logical)

 

3 &4)  Watching the vids all makes sense to me. I know I could do the work and there are not many specialty tools there.  I just don't know that I want to do the work many times over to get the valving right.

 

There are so many "stack recipes" on that thread it really just gets worse the more you read.  I wish there was a good consensus there--kind of like everyone agrees that say the Unabiker rad guards are the best bet for the DRZ

 

I still want to do it

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Oh, i responded to those questions on the other forum you asked.  Sort of the same answers as Athon, only he stated them a little more eloquently.

And the reason there's so many stack recipie's and no concensus, is every likes something a little different, their different weights, skill levels, ride different terrain even different oil viscocity's and brands will make a difference.

Figure out where in the valving you want to improve and concentrate on that area.

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In regard to #2 above.  I actually think the piece of PVC "spacer" would go on the shaft of the damper piston rod.  Part #16 in the fiche.  Push the rod and piston out of the rebound damper tube through the bottom, then add the spacer to the piston shaft, and put it back up in the rebound damper tube?  Thereby the piston rod is shorter effectively pulling the fork down.?...   Of course then oil volume changes, but not oil height??

Screen Shot 2016-02-20 at 9.06.33 PM.png

Edited by kevvyd

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Oh, i responded to those questions on the other forum you asked.  Sort of the same answers as Athon, only he stated them a little more eloquently.

And the reason there's so many stack recipie's and no concensus, is every likes something a little different, their different weights, skill levels, ride different terrain even different oil viscocity's and brands will make a difference.

Figure out where in the valving you want to improve and concentrate on that area.

 

Yeah Bucket,  Thanks again!  Sorry about the thread jacking.  In reading through this do you see any gross errors?  And can you shed some light on spring length, and where to add that spacer to shorten the fork?  Like in the diagram and question/statement above

Edited by kevvyd

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Ya you got the right idea with the spacer, and the oil volume should should only change by as much as the spacer displaces, for the same oil height.

Sorry, i didn't realize you were talking forks when i said about the rear spring being easily adjustable for the shortened shock. And i forgot the forks don't have a large preload spacer in them as many others do, so if you shorten these forks you will have to get shorter springs. I'm dating myself now , but back in the 70's when the selection of aftermarket fork springs was slim, i had cut some of the coils off with a cutting torch and added spacers to replace the coils and effectively increase the spring rate, but unless you can get the spring end bent and ground flat, you'll end up with the coils rubbing too much on the inner tubes and of course you'd have to calculate coil bind.

It seems like you really know your stuff, just a little leary about diving in cause you don't know how deep the water is. But i think once you get things apart and study them for a while you'll figure things out, then just ask some questions if you get stuck.

 

And one other thing, i've been able to pull the fork tubes up 3/4" in the clamps without my tall 3.25x21 tire rubbing the fender when i bottom the forks. If you run a smaller tire you may be able to pull them up 1".

Edited by bucket list

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Ya you got the right idea with the spacer, and the oil volume should should only change by as much as the spacer displaces, for the same oil height.

Sorry, i didn't realize you were talking forks when i said about the rear spring being easily adjustable for the shortened shock. And i forgot the forks don't have a large preload spacer in them as many others do, so if you shorten these forks you will have to get shorter springs. I'm dating myself now , but back in the 70's when the selection of aftermarket fork springs was slim, i had cut some of the coils off with a cutting torch and added spacers to replace the coils and effectively increase the spring rate, but unless you can get the spring end bent and ground flat, you'll end up with the coils rubbing too much on the inner tubes and of course you'd have to calculate coil bind.

It seems like you really know your stuff, just a little leary about diving in cause you don't know how deep the water is. But i think once you get things apart and study them for a while you'll figure things out, then just ask some questions if you get stuck.

 

And one other thing, i've been able to pull the fork tubes up 3/4" in the clamps without my tall 3.25x21 tire rubbing the fender when i bottom the forks. If you run a smaller tire you may be able to pull them up 1".

 

And thank you once again.

 

I am thinking more and more that I will do this job myself.  What I am now realizing is that almost no matter what, I am going to adjust shim stacks.  Getting over the fact that we all only like to do a job 1 time and have it be right is hard to do!!  Going with the mindset that I'll do it, ride it a few months, pay close attention to what I might prefer, and make adjustments a few times over the course of say the next year to end up with a ride that is exactly right for the rider makes it easier to want to do.  (I think I was imagining myself like re-doing the jobs 3 times in a week, which would be not be sufferable)  Also 2 more thoughts are influencing me.  1--I doubt i will make it worse!  2--The best upgrade in the world is a great suspension.  Which I can and hope to end up with...

 

So really spring length and rate is what I am left to figure out.  And honestly I am kind of lost on that.  Its like sure, I can just run the #'s on Race Tech's calculator...but that gives me a rate for the stock length.  (and I am going to need a shorter spring) 

 

Thinking about it:  Take the OEM spec for spring length uncompressed from OEM service manual.  Subtract from that the same amount as the travel reducing spacer--25 mm.  And that will be my required and desired spring size?!?!...  Then find a spring in that length, proper diameter, etc.  But would that (shorter) spring be rated at what is suggested for weight if the suspension were stock length--or would I want the shorter spring to be a little higher rate? (i think so?)

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Sorry I have not read all the previous answers in detail so some of this may have been covered.

 

Yes by all mean do the job yourself.  I think you have the capability.

 

1- Front suspension requires a shorter spring.  Shorter or slightly more (you can always add spacers) by the amount you lower the suspension.  I recommend not more then 2" but 2" is OK.  You can cut the existing spring or buy a shorter spring. Cutting of course creates a stiffer spring.  I do not recommend a stiffer spring due to the lowering. If you need stiffer due to your weight and load OK, but you want the suspension to remain compliant.  You can control bottoming with damping and air chamber volume.  Rear does not require a shorter spring, there is enough length adjustment to use the original spring.  The linkage will already be in a higher rate position so the original spring rate will be OK if it is OK now.

2-When you get the shock apart you will see where a spacer is required and how to make it,  What you are doing is shortening the shock.  It will not extend to its full length.  Some suspension shops add a spacer, some (like me) make a new part that is thicker.

3--How many specialty tools will I need to buy to do the rear shock,-----None that I can think of.   If you remove the seal head from the shaft, you will need a thimble or improvise to reinstall it so as not to cut the seal lip.

4--Should I just send it out.  -----No, do it yourself.  Really pretty simple even if you need to pay a machine shop to make the spacer.  No black magic

5-  Once again, no magic.  If you understand mechanical devises you understand suspension.

 

Front suspension mod is just a spacer to limit the extension. It will bump against the top-out spring. The spacer can be steel , aluminum or hard plastic.  PVC plumbing pipe is really not good enough in my opinion.  I prefer to not have the spacer float on the damper rod so either it fits snug or I secure it with a set screw.

 

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And thank you once again.

 

I am thinking more and more that I will do this job myself.  What I am now realizing is that almost no matter what, I am going to adjust shim stacks.  Getting over the fact that we all only like to do a job 1 time and have it be right is hard to do!!  Going with the mindset that I'll do it, ride it a few months, pay close attention to what I might prefer, and make adjustments a few times over the course of say the next year to end up with a ride that is exactly right for the rider makes it easier to want to do.  (I think I was imagining myself like re-doing the jobs 3 times in a week, which would be not be sufferable)  Also 2 more thoughts are influencing me.  1--I doubt i will make it worse!  2--The best upgrade in the world is a great suspension.  Which I can and hope to end up with...

 

So really spring length and rate is what I am left to figure out.  And honestly I am kind of lost on that.  Its like sure, I can just run the #'s on Race Tech's calculator...but that gives me a rate for the stock length.  (and I am going to need a shorter spring) 

 

Thinking about it:  Take the OEM spec for spring length uncompressed from OEM service manual.  Subtract from that the same amount as the travel reducing spacer--25 mm.  And that will be my required and desired spring size?!?!...  Then find a spring in that length, proper diameter, etc.  But would that (shorter) spring be rated at what is suggested for weight if the suspension were stock length--or would I want the shorter spring to be a little higher rate? (i think so?)

 

Kev, i think you just have to decide what type of riding you do and how you want the bike to feel. I agree with Noble in that the Racetech recommended spring will probably work good for you with the inch less travel, IF your just trail riding at lower to medium speeds. BUT if your going to be doing much higher speed riding with larger bumps, you should probably go up a point or two from the recommended spring rate. (like from .47-.49kg)

 

I believe that most people that work on these DRZ forks agree that they can benifet from increasing the high speed comp. damping part of the valving. I'm not fond of raising the oil level much beyond stock to help with the bottoming, cause i just don't like the feel of the hyper ramped up progressive stiffness near the end of the travel, but that may just be me.

 

And i would get a spring a little shorter than 1" less than stock so you've got some room to play with the preload spacers. Racetech could tell you if you have to worry about coil bind or you could calculate it yourself.

Edited by bucket list
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Umm conflicting info here.

 

The OEM service guide lists the fork spring free length at 2 very different measures (see pics)

 

Race Tech length is stated at 508 mm

 

What do you think.  Or better yet, do you have a service manual or experience that is more reliable.

 

 

 

Susp.jpg

IMG_1698.JPG

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There are 3 different forks used on various DRZ400.  The early S fork, all E, kicker, and S when they got the E fork (2002 I think) and of course the SM fork.  Also keep in kind there are errors in the Suzuki service manual.  My 2000 E service manual says original free length is 510mm which I believe is correct.  You can always measure your springs to verify.

 

http://mx-tech.com/  I think you will find springs of various lengths here.

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I was fuzzy and incorrect and guessy in my first post here! I feel kind of guilty about it but I'll keep doing it a bit :) Hopefully a disclaimer is enough.

 

I believe you can use any spring that has the same travel as the suspension before the coils smash into each other. If that spring is shorter than the space the spring has at full extension, you can just "top up" with a spacer. Meaning you don't have to follow the stock spring dimensions EXACTLY. Just find out the important parameters and make whatever you have work within those bounds.

 

From my naive understanding of what I've read - not least the Shim Restackor site - you want a spring on the stiff end of things, such that you can build a valve stack that

 

A) has controlled but fast-acting damping (combo of spring and valving - stiff spring and low compression damping means faster action over an obstacle of height X, compared to a soft spring and stiffer (slower!) damping) - see here: http://www.shimrestackor.com/Code/Sample_Applications/Spring_Selection/spring-selection.htm

 

B ) allows you to use your suspension travel effectively (mostly the spring, given that the valving doesn't slow wheel travel so much that it doesn't allow the wheel to float over obstacles in time)

 

C) doesn't bottom out all the time, of course

 

and D) keeps the front end at a useful height on average.

 

 

The stock front springs are way soft, and it has an old-style setup of a soft spring and lots of damping. This creates the wallowy, uncontrolled, slow-acting stock suspension. The rear spring is comparatively stiffer! - the E rear spring is softer, the S has a stiffer rear spring which is afaik believed to be because of the passenger pegs.

 

 

People have been going to lots stiffer front high-speed compression damping in the big revalve thread, and I REALLY liked reducing the low-speed compression damping too. And reducing the rebound damping. All this fits very well with a stiffer spring. Plus you are lowering the bike, reducing travel, and if you want to try to combat bottoming you might want to tend towards a proportionately stiffer spring to be able to keep the fast but controlled compression valving which brings about plushness.

 

 

I'd maybe just stick with the stock spring to start with?. And see what you like? From memory there's lost of surplus travel in it before you see any coil bind. Or just buy a new spring - I'd look up recommendations and go for the stiffer side of those recommendations for your purpose. (It'll happen to fit better with the rather stiff but good rear spring.) Just check the amount of travel and try to dig up the length of the spring as it sits in the fork at full extension, and figure out what that length is after you've shortened the travel. I'm inclined to believe any of the recommended springs will work even w/ reduced travel.

 

 

Hope these speculations help!

Edited by Anthon Berg
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I was fuzzy and incorrect and guessy in my first post here! I feel kind of guilty about it but I'll keep doing it a bit :) Hopefully a disclaimer is enough.

 

I believe you can use any spring that has the same travel as the suspension before the coils smash into each other. If that spring is shorter than the space the spring has at full extension, you can just "top up" with a spacer. Meaning you don't have to follow the stock spring dimensions EXACTLY. Just find out the important parameters and make whatever you have work within those bounds.

 

From my naive understanding of what I've read - not least the Shim Restackor site - you want a spring on the stiff end of things, such that you can build a valve stack that

 

A) has controlled but fast-acting damping (combo of spring and valving - stiff spring and low compression damping means faster action over an obstacle of height X, compared to a soft spring and stiffer (slower!) damping) - see here: http://www.shimrestackor.com/Code/Sample_Applications/Spring_Selection/spring-selection.htm

 

B ) allows you to use your suspension travel effectively (mostly the spring, given that the valving doesn't slow wheel travel so much that it doesn't allow the wheel to float over obstacles in time)

 

C) doesn't bottom out all the time, of course

 

and D) keeps the front end at a useful height on average.

 

 

The stock front springs are way soft, and it has an old-style setup of a soft spring and lots of damping. This creates the wallowy, uncontrolled, slow-acting stock suspension. The rear spring is comparatively stiffer! - the E rear spring is softer, the S has a stiffer rear spring which is afaik believed to be because of the passenger pegs.

 

 

People have been going to lots stiffer front high-speed compression damping in the big revalve thread, and I REALLY liked reducing the low-speed compression damping too. And reducing the rebound damping. All this fits very well with a stiffer spring. Plus you are lowering the bike, reducing travel, and if you want to try to combat bottoming you might want to tend towards a proportionately stiffer spring to be able to keep the fast but controlled compression valving which brings about plushness.

 

 

I'd maybe just stick with the stock spring to start with?. And see what you like? From memory there's lost of surplus travel in it before you see any coil bind. Or just buy a new spring - I'd look up recommendations and go for the stiffer side of those recommendations for your purpose. (It'll happen to fit better with the rather stiff but good rear spring.) Just check the amount of travel and try to dig up the length of the spring as it sits in the fork at full extension, and figure out what that length is after you've shortened the travel. I'm inclined to believe any of the recommended springs will work even w/ reduced travel.

 

 

Hope these speculations help!

 

Good Stuff Anthon, Thanks!

 

So the OEM spring is .44kg

When I run my #'s on on Race Tech they suggest a .46kg  (this is of course with stock travel)

 

I been thinking because my weight is coincidentally very close to how it is sprung OEM that I may be able to  get away with the OEM spring.

 

How about these ideas:

1--OEM spring is .44 kg  If I were to chop (for lowering reasons) the coil some it would become stiffer which is desirable.  I do not yet know what % stiffer it would become having not counted coils or had the spring out to measure. 

2--If I spaced the fork travel down by say 25 mm.  That would put 25 mm of preload on an the uncut OEM spring.  Also rendering it stiffer. (yes, no?)  The % stiffer there is beyond my mathematical ability!

 

Also--In looking at replacement springs dimensions I have gathered these facts.

The RTech spring is stated to have on OD of 43.2 mm and 508 length

Other Rtech (lowering--shorter) springs near to that diameter are:    42.7x493, and 43.6x480

--Does the fraction of a MM difference in OD affect anything?

--493  is not much shorter at all,  and 480 is a little shorter than I wanted.  (508 minus 25=483)  If you had to pick an aftermarket spring for lowering 25 mm, which of these is the better choice.

(both springs are available in the .46kg rate suggested)

--MX Tech as noble suggested offers springs in almost the exact same dimensions. (guessing these are applications for other popular models)

 

And yes, I know I should just call Race Tech, but what fun would that be for you guys!  

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1--OEM spring is .44 kg  If I were to chop (for lowering reasons) the coil some it would become stiffer which is desirable.  I do not yet know what % stiffer it would become having not counted coils or had the spring out to measure. 

 

2--If I spaced the fork travel down by say 25 mm.  That would put 25 mm of preload on an the uncut OEM spring.  Also rendering it stiffer. (yes, no?)  The % stiffer there is beyond my mathematical ability!

 

 

1) Some say it's easy to cut springs, some say it's a bit of a bitch to do it correctly :) At least you want to finish the end correctly ... I'd put the spring cutting on ice for now. (It's actually pretty easy to pull a fork apart and you learn a lot and understand everything A LOT better afterwards.) The number of active coils left vs. the original number of active coils is the stiffness change. So quite easy to figure out once you've measured things and had a look.

 

2) Preloading DOES NOT change spring stiffness :) It would if we had progressive springs, but we have linear springs in our bikes and no preload changes any stiffness calculation. Makes everything a heck of a lot simpler :)

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With a 28" inseam - why would you only lower 1"?  2" will be a lot better for you, same amount of work and expense with little if any loss of compliance in suspension.  2" lower you still have 10" of travel on both ends

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With a 28" inseam - why would you only lower 1"?  2" will be a lot better for you, same amount of work and expense with little if any loss of compliance in suspension.  2" lower you still have 10" of travel on both ends

You're right, and as it turns out lowering more than 1" is easier because of the dimensions of aftermarket springs available.  

Noble--Earlier you mentioned getting a metal spacer with a set screw rather than using PVC.  I agree that is a good idea and would have no issue making one.   Any chance you can tell me APX. what dimension the ID of that spacer would be?  And APX. max OD?

 

1) Some say it's easy to cut springs, some say it's a bit of a bitch to do it correctly :) At least you want to finish the end correctly ... I'd put the spring cutting on ice for now. (It's actually pretty easy to pull a fork apart and you learn a lot and understand everything A LOT better afterwards.) The number of active coils left vs. the original number of active coils is the stiffness change. So quite easy to figure out once you've measured things and had a look.

 

2) Preloading DOES NOT change spring stiffness :) It would if we had progressive springs, but we have linear springs in our bikes and no preload changes any stiffness calculation. Makes everything a heck of a lot simpler :)

 

I called Race Tech today.  Dude there advised me that shorter springs will be required for lowering, and that if they were not the coils will bash the inside of the fork.

Also he informed me of the spacing ratio of the rear shock.  8mm internal shock spacing = 25 mm rear wheel travel.  (just FYI)

 

Additionally I am wanting a stiffer spring anyway, so I will be buying a spring 1 rate stiffer (.46) and 472 mm. (36 mm lowering)

 

For now--some fluid questions:  In my forks I use Torco RFF 5 wt fluid.  I know fork and shock oils have different properties.  (Torco makes an RSF fluid for shocks)  Questions--

1--Would it be OK to use the same fluid in the rear shock as in the fork? 

2--When you tell me NO what is the advised oil weight for the rear shock on the DRZ? (Torco RSF comes in Light and Medium--4.70 cSt and 9.57cSt respectively)

3--Apx. what volume of fluid is the rear shock going to take.  And will it be less because the shock is lowered?  

Edited by kevvyd
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For now--some fluid questions:  In my forks I use Torco RFF 5 wt fluid.  I know fork and shock oils have different properties.  (Torco makes an RSF fluid for shocks)  Questions--

1--Would it be OK to use the same fluid in the rear shock as in the fork? 

2--When you tell me NO what is the advised oil weight for the rear shock on the DRZ? (Torco RSF comes in Light and Medium--4.70 cSt and 9.57cSt respectively)

3--Apx. what volume of fluid is the rear shock going to take.  And will it be less because the shock is lowered?  

 

 

Love this thread! thanks for starting it!

 

I don't know if it's OK to use shock oil in forks and vice versa. Probably? But! I'll say that the front valves really like lighter oil. (With a new shim stack.) Stock front is 5W. I have 2.5W in mine, and might have tried 0W if I had been able to find it locally. What happens with thinner oil in the front is that rebound damping is reduced overall (good, rebound is said to be overdamped and it makes sense to me), lowspeed compression is reduced quite a bit which is very good (much improves smoothness over trail trash but can still be brought up again with the clicker), but highspeed compression isn't affected very much (damping here is "owned"/dominated by the valve stack). What the front revalve mostly does is bring up the highspeed compression - and second, we want to reduce rebound damping and lowspeed compression damping a bit. The thinner oil strategically helps reduce damping where we want it reduced, and then we bring up the highspeed damping with new valve shims.

 

It's quite simple actually :) I hope I'm not making it seem more complex than it is. I tend to get kinda verbose sometimes.

 

In short I'd advise stock weight for the rear (5W?), and 2.5W for the front if you revalve.

 

I don't know about the rear oil volume or how shorter travel affects it. Good question.

 

You might be able to find some data on the suspension like oil volume etc. in the Clymer manual, if it's not in the Suzuki shop manual.

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Spacer ID will be the diameter of the damper rod.  14mm I think but I don't remember for sure.  As I recall the spacer I made was mushroom shaped (head bigger than the body).  You will figure it out easily when you have it apart.  I used steel since it contacts the top-out spring.

 

Rear shock does not take a lot of fluid.  I'm only guessing, like 8 oz or so.  It is really unimportant. You add oil and burp the air and add oil and burp until as much air as you can get out is out.  Do the best you can, but you will never get it all. However that is also unimportant, the nitrogen pressure will put the small amount of air left into solution.  There are some tricks to filling the shock with oil and getting the bladder in right.   There is probably a video about it.  I inflate the bladder to about 1 or 2 psi to hold its shape. Yes, the modified shock will take less oil by the volume of the spacer you add and the volume of the piston rod that is reduced by the travel.

 

I still recommend 50mm lowering.  If Race Tech does not have the springs, someone else does.  The first time around I lowered 1" and cut the springs.  Second time I lowered 2" and bought springs.  Actually it is better to heat and close coils than to actually cut springs, that way you do not have to deal with closing and squaring the last coil.  But really I do not recommend cutting or closing coils at all.

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Spacer ID will be the diameter of the damper rod.  14mm I think but I don't remember for sure.  As I recall the spacer I made was mushroom shaped (head bigger than the body).  You will figure it out easily when you have it apart.  I used steel since it contacts the top-out spring.

 

Rear shock does not take a lot of fluid.  I'm only guessing, like 8 oz or so.  It is really unimportant. You add oil and burp the air and add oil and burp until as much air as you can get out is out.  Do the best you can, but you will never get it all. However that is also unimportant, the nitrogen pressure will put the small amount of air left into solution.  There are some tricks to filling the shock with oil and getting the bladder in right.   There is probably a video about it.  I inflate the bladder to about 1 or 2 psi to hold its shape. Yes, the modified shock will take less oil by the volume of the spacer you add and the volume of the piston rod that is reduced by the travel.

 

I still recommend 50mm lowering.  If Race Tech does not have the springs, someone else does.  The first time around I lowered 1" and cut the springs.  Second time I lowered 2" and bought springs.  Actually it is better to heat and close coils than to actually cut springs, that way you do not have to deal with closing and squaring the last coil.  But really I do not recommend cutting or closing coils at all.

 

 

--I did not think the fork had a top-out spring?  Is it just not shown on the fiche because it is inside the damper tube?  It is 2004 fork.  Air bleeder and rebound on top cap.

--I am going to take your advice and go with 50 mm lower springs.  Still leaves me with 9.3" travel.  Plenty more than many DS bikes...I guess I was worried about ground clearance.  But in reality     I am not gonna do too much true woods or MX riding where that comes into play.

--Are you saying/thinking it is fine to use 5wt "Fork" fluid in the rear shock.  I have 2 liters of that and it would be enough to do all 3 chambers even if they were not lowered, so...

--Would you recommend a lighter weight oil for the fork?  I already have Torco 5wt--5.05 cSt but do not have to use that, or could mix it to a lighter weight

--Is the rear shock seal "bullet" really worth it,  or would wrapping the threads in tape or something be sufficient? $15 for something I may use 2 times?

--Same question about the seal head pushing tool..worth it @ $40  for a seldom used piece?

Very grateful for your help and advice. 

Edited by kevvyd

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