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Old March 31st, 2015, 10:11 AM   #1
ieathonda
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Fork oil weight/spring rate

Im going to be servicing the forks soon since my right fork is leaking and getting a generous amount of oil on the wheel/brake caliper and rotor (YIKES). I know the stock oil is 5W, should I upgrade and try 10W?

I will also be replacing the stock springs with either ex500 or custom sonic/race tech and possibly emulators as well. I weigh in at 145 without gear and it calculated that I need a .641.

What are your setups and experience with changing oil weights? Thanks
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Old March 31st, 2015, 10:54 AM   #2
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Im going to be servicing the forks soon since my right fork is leaking and getting a generous amount of oil on the wheel/brake caliper and rotor (YIKES). I know the stock oil is 5W, should I upgrade and try 10W?

I will also be replacing the stock springs with either ex500 or custom sonic/race tech and possibly emulators as well. I weigh in at 145 without gear and it calculated that I need a .641.

What are your setups and experience with changing oil weights? Thanks


Homework time, http://www.ex-500.com/wiki/index.php...the_Suspension
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Old March 31st, 2015, 11:20 AM   #3
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Stock should be pretty close to your weight.
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Old March 31st, 2015, 12:23 PM   #4
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I read everything i could on the ninja wiki. I will replace the fork seal and change the oil to 5W. The PO does not even know when the last time the fork oil was changed and i want to say probably never.

Im still thinking about the emulators and wondering if they will be worthwhile at the moment..
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Old March 31st, 2015, 02:59 PM   #5
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I personally would increase the fork oil to 15wt.

I run it on my Ninjette, and it seems to work good.

I weigh with gear about 225lbs I've also installed and cut EX500 springs, and set the sag dead on.

Remember to add and set the oil level properly, as this is one of the most thing that is messed up.

As far as emulators go, I don't have them, and if I wanted them I would do the FOG trick as per the EX-500.COM wiki.

Quote:
AT My home racetrack there were two places that the forks bottomed out even after I got the ride I wanted everywhere else. The control This I added another short set of springs down inside of the main spring. I used 2 of the inner valve springs in each fork. These springs were operated by a Length of 1/2" PVC pipe inside of the 1" cut to a length that would just cause them. to come into play near the bottom of fork travel. Thereby adding there rate to the main spring and stiffening the whole thing to prevent bottoming with out making the normal ride too stiff.
BTW this is what the Race Tech Emulators do for 130 bucks or more
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Old March 31st, 2015, 03:08 PM   #6
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Some more homework for you, if you haven't looked already,

http://faq.ninja250.org/wiki/Front_suspension_upgrades
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Old March 31st, 2015, 07:17 PM   #7
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Try the oil. Worse case you change it. If 10 too stiff try 5w on one side 10 on other.
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Old March 31st, 2015, 07:20 PM   #8
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Try the oil. Worse case you change it. If 10 too stiff try 5w on one side 10 on other.
What??????

Both sides must match, go with the 15wt


Torco T830015CE RFF 15 Racing Fork Fluid Bottle - 1 Liter https://www.amazon.com/dp/B000WMO6NS..._nx1gvb1GQTTZH


I run 30wt in my ninja 500 even, 15wt is not too thick
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Old March 31st, 2015, 07:37 PM   #9
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What??????

Both sides must match, go with the 15wt
no they don't.
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Old March 31st, 2015, 07:40 PM   #10
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no they don't.
Yep... they don't.
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Old March 31st, 2015, 07:47 PM   #11
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News to me then, I would think that having the two forks reacting differently would be a problem, like uneven amounts of fork oil? Having the two reacting differently would/might effect the the front wheel geometry, angle, etc......

I'm old, but will to learn..... Mostly, let's see some data gentlemen.
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Old March 31st, 2015, 07:54 PM   #12
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News to me then, I would think that having the two forks reacting differently would be a problem, like uneven amounts of fork oil? Having the two reacting differently would/might effect the the front wheel geometry, angle, etc......

I'm old, but will to learn..... Mostly, let's see some data gentlemen.
Lets see yours first. And you must apologize for mocking me.
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Old March 31st, 2015, 07:58 PM   #13
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@crazymadbastard

I didn't mean to mock you, no disrespect intended, my apologies if I did



I'll be back with data , unless @InvisiBill is around to lend a hand.
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Old March 31st, 2015, 08:02 PM   #14
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@crazymadbastard

I didn't mean to mock you, no disrespect intended, my apologies if I did



I'll be back with data , unless @InvisiBill is around to lend a hand.
Don't worry about it, I forgive but reserve the right to mock you at the most appropriate moment.
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Old March 31st, 2015, 08:07 PM   #15
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Don't worry about it, I forgive but reserve the right to mock you at the most appropriate moment.
Agreed
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Old March 31st, 2015, 08:13 PM   #16
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Lets see yours first.
I been waiting for this one for a looooong time.
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Old March 31st, 2015, 08:21 PM   #17
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I've mixed fork oil of different weights to achieve a different weight, but never tried different weights in each fork.

Looks like I have some homework to do.
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Old March 31st, 2015, 08:31 PM   #18
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Still looking, I've found references for automotive, like racing applications, NASCAR, etc.... But that makes sense to me.
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Old March 31st, 2015, 08:34 PM   #19
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I been waiting for this one for a looooong time.
<3
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Old March 31st, 2015, 08:50 PM   #20
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Still looking, so far no luck, no mention of different weights per fork leg.

http://racetech.com/page/id/30
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Old March 31st, 2015, 09:22 PM   #21
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As far as emulators go, I don't have them, and if I wanted them I would do the FOG trick as per the EX-500.COM wiki.
Quote:
Originally Posted by FOG
AT My home racetrack there were two places that the forks bottomed out even after I got the ride I wanted everywhere else. The control This I added another short set of springs down inside of the main spring. I used 2 of the inner valve springs in each fork. These springs were operated by a Length of 1/2" PVC pipe inside of the 1" cut to a length that would just cause them. to come into play near the bottom of fork travel. Thereby adding there rate to the main spring and stiffening the whole thing to prevent bottoming with out making the normal ride too stiff.
BTW this is what the Race Tech Emulators do for 130 bucks or more
I've seen that before, and I don't believe it.

The emulators have holes similar to the stock damper rods which control the flow of the oil, just as the stock setup does. However, it also adds a bypass valve with a spring. When you hit a big bump or something and the forks are trying to quickly compress, that pressure overcomes the spring and allows the oil to flow through quickly (instead of only being able to use the standard small holes). You can change the rate and preload of the spring to alter how the bypass valve behaves.

I'm not sure how adding some extra "anti-bottom-out" springs is equivalent to adding more advanced damping control. I'm thinking it's more a case of FOG was bottoming out, and someone told him emulators would fix it. Instead of spending $130 to slightly tweak the suspension performance to fix that one specific problem, he did it with some parts he had sitting around. Sure, that problem might be fixed just as well either way, but I don't see how anyone could consider those two mods to be "the same thing".


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Im still thinking about the emulators and wondering if they will be worthwhile at the moment..
Personally, I bought emulators, then sold them to buy Ricor Intiminators (about $50 more). https://www.ninjette.org/forums/showthread.php?t=186192 has a lot of info on them (as does the instruction post linked from it). In my mind, they're a much more sophisticated solution. The inertia valve should open only from the wheel pushing up, not the chassis pushing down; the emulators will open up anytime the pressure exceeds the spring. The emulators duplicate the fixed orifices of the (crappy) stock damper rod setup for main compression control; the Intiminators use a shim stack like modern cartridge forks. I think of them sort of like carbs and FI. The emulators have been around quite a while and a lot of people have a good handle on how to tweak them for best performance. Intiminators are newer and have more stuff to figure out, but once you do learn the system, it has a lot more potential.

Getting springs to match my weight was the best mod I've done. The Intiminators smoothed things out even more, but the springs were half the cost and more of an improvement. If you go the Intiminator route, they're easier to install since they don't require drilling out the damper rods (but they might work better if you do), so you could even add them in later if you wanted.
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Old March 31st, 2015, 09:23 PM   #22
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Old March 31st, 2015, 09:27 PM   #23
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Hey @InvisiBill what's your take on the different weights for each fork?
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Old April 1st, 2015, 02:21 AM   #24
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Fwiw: stock fork oil is 10W. I dropped to 5W for my Intiminators to render the dampers nearly useless. I'm even sea sting drilling them to be sure about it.
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Old April 1st, 2015, 03:45 AM   #25
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Before talking about the weight of fork oil I would recommend reading this http://www.peterverdone.com/wiki/ind...spension_Fluid
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Old April 1st, 2015, 07:24 AM   #26
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Hey @InvisiBill what's your take on the different weights for each fork?
*shrug* I don't know that much about this stuff.

It seems like having different oil in the two separate forks which are supposed to work in unison could cause issues, since each side would want to behave slightly differently. It just seems like one side would want to compress faster than the other or something, resulting in the axle not wanting to stay perpendicular. I think that's the sort of thing you were getting at.

But if the hard parts provide enough rigidity to keep everything properly aligned, then you might be able to use different oils in each fork and use the slightly different behavior to tweak one for compression and one for rebound or something. But every situation I can think of with my understanding of our simple damper rod forks, you could achieve the same thing by tweaking the flow circuits, which would allow you to run the same oil on both sides and avoid the possibility of imbalances. Perhaps for testing to figure out the best feel before modifying the circuits?

P.S. The non-symmetry would eat away at my OCD brain.
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Old April 1st, 2015, 07:31 AM   #27
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So interesting thought on the fork oil discussion, you can put different weight oil in each leg and you can put different spring rates in each leg as well. You have have one leg do all the springing and one leg do all the dampening. You can also split rebound and compression duties on legs as well. The two legs in the broad scheme of things act as one system due to the rigid mounting between the two.

On that note however I was just thinking about the different weight oil setup in the forks and wonder if there may actually be an advantage/disadvantage to doing that verses a blend in both legs.

Fixed orifice fluid dampening like in the ninjette is a factor of surface area of the orifices and the viscosity of the fluid in relationship to velocity of the fluid movement. As the fluid velocity doubles the dampening force increases four times, it is a squared relationship.

The volume displacement of the fork stroke will be the same for both legs as will the stroke velocity of the fork. So lets assume that A = dampening force of leg 1 and B = dampening force of leg 2. And X = dampening force at fork stroke velocity.

So at Y, X = A + B and at 2Y, X = A^2 + B^2

For giggles lets assume that fork oil in A and B are the same and for that fork oil at Y velocity the you get 2 units of force from fluid in each leg. So at Y, you get X=4 and at 2Y, X=8.

Now lets assume that fork oil in A at Y provides the result of X=2 and at Y the oil in B X=4. So at Y, X=2+4=6 and 2Y, X=2*2+4*4=20

Now lets assume that you mix A and B oil so you get C and its halfway between so at Y, C oil provides X=3 from each leg

now at Y, X=3+3=6 and 2Y, X=3*3+3*3=18

So actually after InvisiBill pointed my error, there is a difference at high speed displacement dampening from going with a different weight in each leg vs a mix. In this case a 10% increase at double the stroke velocity.

And I think I also better point out that the difference in high velocity dampening will diverge even greater the more different the viscosity is between the two fluids. When one had twice the resistance we got a 10% increase in dampening vs mixing. If you went four times, the difference at 2Y would be nearly 27%. At Y X=2+8=10, at 2Y X=2^2+8^2=68; mixed at Y X=5+5=10; 2Y X=5^2+5^2=50.
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Old April 1st, 2015, 07:33 AM   #28
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Should be no compression issues as the fluid is "in-compressible". It is about volume movement and velocity. They work together as a summation of forces. Same with springs. The forks are the same so chamber volumes change at the same rate and we assume fluid level is the same so volume change is the same.
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Old April 1st, 2015, 09:34 AM   #29
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So interesting thought on the fork oil discussion, you can put different weight oil in each leg and you can put different spring rates in each leg as well. You have have one leg do all the springing and one leg do all the dampening. You can also split rebound and compression duties on legs as well. The two legs in the broad scheme of things act as one system due to the rigid mounting between the two.

On that note however I was just thinking about the different weight oil setup in the forks and wonder if there may actually be an advantage/disadvantage to doing that verses a blend in both legs.

Fixed orifice fluid dampening like in the ninjette is a factor of surface area of the orifices and the viscosity of the fluid in relationship to velocity of the fluid movement. As the fluid velocity doubles the dampening force increases four times, it is a squared relationship.

The volume displacement of the fork stroke will be the same for both legs as will the stroke velocity of the fork. So lets assume that A = dampening force of leg 1 and B = dampening force of leg 2. And X = force at fork stroke velocity.

So X = A + B and 2X = A² + B²

For giggles lets assume that fork oil in A and B are the same and for that fork oil at that X velocity the you get 2 units of force. So at X, you get X=4 and 2X=8.

Now lets assume that fork oil in A at X=2 and B at X=4 so X=6 and 2X=2²+4²=18

Now lets assume that you mix A and B oil so you get C and its halfway between C=3

now X=3+3=6 and 2X=3²+3²=18

So math tells me no difference at all.
I cleaned that up with "²" to make it a little less confusing... You're also reusing X for different things, but that's a little more work to straighten out.

You might want to double-check your math on 2² + 4² = 18.


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Originally Posted by sharky nrk View Post
Should be no compression issues as the fluid is "in-compressible". It is about volume movement and velocity. They work together as a summation of forces. Same with springs. The forks are the same so chamber volumes change at the same rate and we assume fluid level is the same so volume change is the same.
I wasn't referring to compression of the fork oil, but of the whole fork unit. As your math shows, there's more force involved with compressing one fork than with the other. Even if the overall force to compress the whole front end is the same, the two sides are reacting differently to the input force. Due to the clearances needed for the parts to actually slide, plus manufacturing tolerances, there is a little bit of room for things to get cockeyed. I'm not sure if the assembly is rigid enough to maintain its alignment under these circumstances.

To make an exaggerated example, take the front wheel off your bike and flip it upside down. Now compress the forks by hitting the middle of the axle with a big hammer. The force should be evenly distributed to both forks. Now repeat this, but hit the end of one side's fork leg instead of the middle of the axle. Both forks are "solidly" connected via the axle, but I'm guessing they wouldn't compress exactly evenly, due to real-world imperfections vs. a perfect theoretical world.

Again, I'm no expert, I'm just trying to logic my way through this. Even if you can use different oil weights, I'm having a hard time figuring out any reason you'd want to. For everything I can think of, it seems like you're making two incorrect settings that average out to the correct setting, when you could just set both of them to the correct setting in the first place.
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Old April 1st, 2015, 09:56 AM   #30
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Interesting. So the ricor intimidator would not need modification to the damping rod but some people have drilled it out anyway? I believe cuong drilled it out to 10mm. And does this modification apply to the existing holes or are there additional holes that are drilled like shown in the emulator DIY?

I think I will stick with 5w and get the appropriate spring. I'm not sure if I should get a custom set at .641 or just stick the ex500 and space it out appropriately.
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Old April 1st, 2015, 10:28 AM   #31
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I cleaned that up with "²" to make it a little less confusing... You're also reusing X for different things, but that's a little more work to straighten out.

You might want to double-check your math on 2² + 4² = 18.




I wasn't referring to compression of the fork oil, but of the whole fork unit. As your math shows, there's more force involved with compressing one fork than with the other. Even if the overall force to compress the whole front end is the same, the two sides are reacting differently to the input force. Due to the clearances needed for the parts to actually slide, plus manufacturing tolerances, there is a little bit of room for things to get cockeyed. I'm not sure if the assembly is rigid enough to maintain its alignment under these circumstances.

To make an exaggerated example, take the front wheel off your bike and flip it upside down. Now compress the forks by hitting the middle of the axle with a big hammer. The force should be evenly distributed to both forks. Now repeat this, but hit the end of one side's fork leg instead of the middle of the axle. Both forks are "solidly" connected via the axle, but I'm guessing they wouldn't compress exactly evenly, due to real-world imperfections vs. a perfect theoretical world.

Again, I'm no expert, I'm just trying to logic my way through this. Even if you can use different oil weights, I'm having a hard time figuring out any reason you'd want to. For everything I can think of, it seems like you're making two incorrect settings that average out to the correct setting, when you could just set both of them to the correct setting in the first place.
Ok take the same bike, apply lean angle and have pressure applied more so to the inner turn edge of the tire, my point being that most of the time force is not applied equally but the fork still is forced to move as a unit and averages out.
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Old April 1st, 2015, 10:53 AM   #32
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Quote:
Originally Posted by ieathonda View Post
Interesting. So the ricor intimidator would not need modification to the damping rod but some people have drilled it out anyway? I believe cuong drilled it out to 10mm. And does this modification apply to the existing holes or are there additional holes that are drilled like shown in the emulator DIY?

I think I will stick with 5w and get the appropriate spring. I'm not sure if I should get a custom set at .641 or just stick the ex500 and space it out appropriately.
Spacing the kit doesn't increase spring rate, it just to set the sag.

If you want to increase the rate, you need to cut them to the appropriate length for your new spring rate.

To calculate new spring rate = (original spring length / modified spring length) * original spring rate

So if your getting a set off a 2nd Gen EX (94 & up) the spring is 17" About and cut 2" off your new rate will about .66, then just get some pvc pipe and make new spacers.

SIDENOTE: 1st Gen EX500 (pre 94') use a much longer spring about 20.5" same rate, this gives you more spring to experiment with.

A quick way to figure overall length is the measure the original spring, and spacer total length , this will get you in the ballpark of the OEM setting.

You should cut the new spacers a little bit longer 1" or so you can then trim the down to set the sag.

If you mess up, no worries hopefully you got the 10' pvc pipe, plenty of room to experiment with.

If you want them stiffer, just cut more off the spring, and new spacers.

It's easy to do, as I've done the spring modification to both my EX, and Ninjette(EX springs) and I'm happy with the results and saving some cash as well.
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Old April 1st, 2015, 10:56 AM   #33
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Interesting. So the ricor intimidator would not need modification to the damping rod but some people have drilled it out anyway? I believe cuong drilled it out to 10mm. And does this modification apply to the existing holes or are there additional holes that are drilled like shown in the emulator DIY?
Yes. The Intiminators are designed to run with relatively low weight fork oil, which for the most part bypasses the restriction of the stock holes, effectively neutralizing the stock damping. However, it was pointed out that high speed damping is based on the oil's density rather than viscosity, so it's possible that even the thinner oil could still cause some interference if you leave the stock damper rod holes.

They work great for me and chone without touching the damper rods (yet). If you want to be 100% sure the stock parts aren't doing anything unexpected, drill them out. The idea is to remove the restriction (how damper rods work to control the suspension) by drilling bigger/more holes.


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I think I will stick with 5w and get the appropriate spring. I'm not sure if I should get a custom set at .641 or just stick the ex500 and space it out appropriately.
Do you already have the EX500 springs, or can you get them quite cheap? A standard set of springs is ~$90. I'm not sure how much a custom rate would be on top of that. Ricor suggests that they use a lot of damping, so you can use a lower spring rate, if you're considering the Intiminators. You're close to .65, but may want to consider .60 (still 36% stiffer than stock). At that point, the EX500 springs at .585 (33% stiffer than stock) are pretty darn close if you can get them substantially cheaper. They're nearly useless on the 500 (they should be about 36% stiffer just to match the rear spring for a 130lb rider), so there's a good chance you can find some for next to nothing. There's a lot of value in getting 95% of the way there for $10.

Note that spacers/preload can never make up for a spring of the wrong rate. Preload can take some of the squishy feeling out of a soft spring, but it does so by pre-compressing it toward the bottom ahead of time (pre... loading...) so that it doesn't travel as far in use. The same force on a spring will always compress it down to the same length, determined by the spring's rate, regardless of how much initial preload is on it.
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Old April 1st, 2015, 11:38 AM   #34
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I cleaned that up with "²" to make it a little less confusing... You're also reusing X for different things, but that's a little more work to straighten out.

You might want to double-check your math on 2² + 4² = 18.

OK yeah, that is what I get for typing and posting and thinking all at the same time without double checking on a smartphone lol. Obviously 4+16 is 20 not 18. Apologies. Also after re-reading your correct on the Xs, let me fix one of those to a Y.

How do you superscript the 2 on here?
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Old April 1st, 2015, 11:50 AM   #35
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Originally Posted by InvisiBill View Post
I wasn't referring to compression of the fork oil, but of the whole fork unit. As your math shows, there's more force involved with compressing one fork than with the other. Even if the overall force to compress the whole front end is the same, the two sides are reacting differently to the input force. Due to the clearances needed for the parts to actually slide, plus manufacturing tolerances, there is a little bit of room for things to get cockeyed. I'm not sure if the assembly is rigid enough to maintain its alignment under these circumstances.
Remember though the friction bits and flex and all the other little losses mean very little in the context of the fluid dampening itself. The dampening is the result of displacement of oil, which is the direct result of movement through the stroke of the fork. And that is post losses in friction through tubes and flex in forks and clamps and for all practical purposes the two tubes of the fork legs move the same displacement.
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Old April 1st, 2015, 11:59 AM   #36
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Originally Posted by InvisiBill View Post

Do you already have the EX500 springs, or can you get them quite cheap? A standard set of springs is ~$90. I'm not sure how much a custom rate would be on top of that. Ricor suggests that they use a lot of damping, so you can use a lower spring rate, if you're considering the Intiminators. You're close to .65, but may want to consider .60 (still 36% stiffer than stock). At that point, the EX500 springs at .585 (33% stiffer than stock) are pretty darn close if you can get them substantially cheaper. They're nearly useless on the 500 (they should be about 36% stiffer just to match the rear spring for a 130lb rider), so there's a good chance you can find some for next to nothing. There's a lot of value in getting 95% of the way there for $10.

Note that spacers/preload can never make up for a spring of the wrong rate. Preload can take some of the squishy feeling out of a soft spring, but it does so by pre-compressing it toward the bottom ahead of time (pre... loading...) so that it doesn't travel as far in use. The same force on a spring will always compress it down to the same length, determined by the spring's rate, regardless of how much initial preload is on it.

I do not currently have them. A few sellers on ebay have a fork set for sale for 1/2 the price of the springs alone (new, couldnt find used fork springs by themselves). the only problem is i havent ogtten any information back on them to see if the fork sets have the springs as well. its about 30-50 dollars for a used fork set from ebay.

My initital plan is to just drop in the ex500 spring. depending on what year i get i will have to cut the spacer correctly to size..

I havent taken apart the forks yet so i do not know of where all of the components sit just yet. I only can reference back to diagrams and such online.

So will the ex500 be a drop in? From my understanding i should take the original spring and spacer total length, then measure the ex500 spring and make a spacer appropriately so that the ex500 spring and new spacer come out to the same total length of the stock spring and spacer, correct?
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Old April 1st, 2015, 12:15 PM   #37
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For everything I can think of, it seems like you're making two incorrect settings that average out to the correct setting, when you could just set both of them to the correct setting in the first place.
It seems after revisiting my hurried post the only real potential benefit I could see would be that you could increase your high speed dampening relative to your low speed dampening vs mixing the oils (or a different consistent rate)

The problem with that is basically that is like the opposite of what you want lol, I mean the you want less dampening at really large displacements so that the suspension can track the surface of the road without jolting you hard and upsetting the chassis and you want higher dampening at the lower displacement speeds to control wallowing and sponginess.

So it would be no benefit at all so you wouldn't want to do it lol.
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Old April 1st, 2015, 01:54 PM   #38
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I do not currently have them. A few sellers on ebay have a fork set for sale for 1/2 the price of the springs alone (new, couldnt find used fork springs by themselves). the only problem is i havent ogtten any information back on them to see if the fork sets have the springs as well. its about 30-50 dollars for a used fork set from ebay.
I would expect any complete fork to contain the spring. The spring is what causes the fork to extend, so any fork assembled without the spring would collapse and not be usable on a bike. The spring tension actually holds the top cap against the snapring, so it couldn't really be fully assembled without the spring.

As for damaged parts, I'm not sure how much force it would take to somehow damage the springs - it seems like even with a pretty severe fork bend, the springs should just "spring" and bend along with it. I'm sure it's possible to wreck bad enough to damage the springs too, but forks with minor damage should be ok, I would think.

After you steal the springs, you might be able to sell some of the remaining components too. Lowers get damaged, people might want undrilled damper rods if they're taking out emulators and putting a bike back to stock, etc.


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I havent taken apart the forks yet so i do not know of where all of the components sit just yet. I only can reference back to diagrams and such online.
Spring swaps are easy. Once you remove the cap, the spacer and spring are right there at the top of the fork. Just pull them out and drop the new ones back in. Emulators and Intiminators sit just under the spring.


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So will the ex500 be a drop in? From my understanding i should take the original spring and spacer total length, then measure the ex500 spring and make a spacer appropriately so that the ex500 spring and new spacer come out to the same total length of the stock spring and spacer, correct?
Supposedly the PreGen 250 and Gen1 500 both have 36mm forks and the NewGen and Gen2 have 37mm forks. However, some diameter-dependent items are shared between at least some of the different sizes. I believe most people are using Gen2 springs, even though they should technically be a little bigger. Someone with a PreGen should be able to verify that the Gen2 springs work.

As for the spacer, that's generally correct, but not precisely. The overall length of the new spring & spacer should be pretty close to the overall length of the old spring & spacer. However, the length of the spacer determines how much preload is placed on the spring, which determines the sag. A different spring rate will inherently require a different length spacer to result in the same amount of sag.

There's a 250 FAQ/Wiki somewhere that says the length of the new parts must be exactly equal to the length of the old parts. I just wanted to point out that this is an oversimplification, and spacer length will vary a little.
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Old April 1st, 2015, 02:25 PM   #39
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the item i am looking at is in good working condition. the only thing tahts wrong with them is the upper fork seals.. all can be had for $20 plus $20 shipping which is a great price...

Spring change doesnt sound too complicated at all then.. although i do have a leaky fork seal that will need to be replaced.

I ran by some preload adjusters that sit on top of the fork. would this be a worth while addition to the front suspension and help me to fine tune the preload? I will be running woodcraft lowered risers in a few weeks as well so the preload adjusters will be accessible.
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Old April 1st, 2015, 02:44 PM   #40
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The PreGen Ninjette and 1st Gen EX springs are a direct replacement, with the exception of the overall length, below it a picture of when I did mine, showing the difference at OEM lengths, with the EX springs being longer, also not the springs themselves are slightly diameter material. I had a replacement set of forks for the EX laying around anyway.


As far as the adjustable preloads go, you could, but to be honest once they're set, you shouldn't need to be adjusting them again. They would add some flash to the top of the tubes, since your going with clip-ons anyway.

I personally just went ZX600C risers to lower mine.

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