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Old 08-12-2018, 10:43 PM   #1
kuksul08
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Damping or Spring Rate?

VStrom 650 - weighs 500lbs wet
Me 190lbs

I recently redid my fork on my bike with some new springs and gold valves. It was really squishy and divey before. The stock setup is a 0.6-0.9kg/mm progressive spring with damping rod. The new springs are .90 straight rate with gold valves at the RT setting.

Right now it still feels like it has a good amount of brake dive when I'm really hammering on the brakes. It feels good in a corner, and feels smooth over bumps. It doesn't deflect on sharp bumps. Doesn't feel harsh. Isn't unstable. It just feels like it still dives too much during that initial braking phase or if I jab the brakes. The weight transfer to the front also means the rear loses grip more readily than I'd like.

I'm having a hard time putting my finger on whether it could use more spring rate or more damping. My only external adjustment is preload. It's unfortunately not very easy to make changes so I'd like some input before I get fork oil all over myself and my bike (again).
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Old 08-13-2018, 03:56 AM   #2
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To simplify: Spring & preload is how far it dives. Damping is how fast it dives. Which one do u want to change?
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Old 08-13-2018, 08:08 AM   #3
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What weight oil did you do? Did you do anything to the damper rod holes?
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Old 08-13-2018, 08:17 AM   #4
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I'm assuming you mean you put in Emulators, not gold valves? They are the ones for damper rod forks. Another variable you may try is fork oil level. A higher fork oil level will increase the air spring effect. I think you will find a level mentioned in the directions for the emulators. You might try increasing the oil amount. If the spring preload is external, that might be you first adjustment. The Emulators are also adjustable, as you probably know, just a pain in butt to get to.

Last edited by bobl; 08-13-2018 at 08:19 AM..
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Old 08-13-2018, 10:45 AM   #5
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Originally Posted by stangmx13 View Post
To simplify: Spring & preload is how far it dives. Damping is how fast it dives. Which one do u want to change?
Hmm. I don't know! It's hard to put my finger on it. I feel like it might be a combination of the two.

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What weight oil did you do? Did you do anything to the damper rod holes?
15W oil. Drilled out the compression holes per the instructions to 5/16" and added 2 more.

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I'm assuming you mean you put in Emulators, not gold valves? They are the ones for damper rod forks. Another variable you may try is fork oil level. A higher fork oil level will increase the air spring effect. I think you will find a level mentioned in the directions for the emulators. You might try increasing the oil amount. If the spring preload is external, that might be you first adjustment. The Emulators are also adjustable, as you probably know, just a pain in butt to get to.
Yeah, emulators (but they're gold too!). I really with the emulators were more easily adjustable.

I put oil height at 145mm. RT recommends 150mm, stock is 140mm. It was in that ballpark. That would be an easy thing to change.



So this morning I added some preload and it does seem to help. It does feel like when I add preload it adds some harshness though.
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Old 08-13-2018, 11:21 AM   #6
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Originally Posted by kuksul08 View Post
Hmm. I don't know! It's hard to put my finger on it. I feel like it might be a combination of the two.

I put oil height at 145mm. RT recommends 150mm, stock is 140mm. It was in that ballpark. That would be an easy thing to change.

So this morning I added some preload and it does seem to help. It does feel like when I add preload it adds some harshness though.
in my experience, too little compression damping is a larger problem than too little spring or preload when it comes to dive.

I doubt ud be able to notice a diff in feel btw 140, 145, or 150mm air gap. a 20-30mm change is more noticeable.

if u aren't absolutely certain u felt a noticeable difference with the preload change, there probably wasn't a big enough change. because of that, id go the other route and add some compression damping. fork dive falls in the low-speed range of fork movement. u cant easily add low-speed compression w/ emulators cuz theres no bleed control. but adding preload to that spring will add some damping in the faster part of the low-speed range. ull feel it.
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Old 08-13-2018, 12:09 PM   #7
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in my experience, too little compression damping is a larger problem than too little spring or preload when it comes to dive.

I doubt ud be able to notice a diff in feel btw 140, 145, or 150mm air gap. a 20-30mm change is more noticeable.

if u aren't absolutely certain u felt a noticeable difference with the preload change, there probably wasn't a big enough change. because of that, id go the other route and add some compression damping. fork dive falls in the low-speed range of fork movement. u cant easily add low-speed compression w/ emulators cuz theres no bleed control. but adding preload to that spring will add some damping in the faster part of the low-speed range. ull feel it.
I think you're exactly right. Fortunately the gold valves can adjust low speed by way of the bleed holes on the plate. Right now I'm at 4 bleed holes. You can run anywhere from 1 to 4 holes. I have another set of plates with 2 holes pre-drilled.

I think the reason they recommended using the 4-hole plate is because people complained of a bouncy ride on rippled surfaces. I feel no bounce at all with the 4-hole plate. When riding over a rippled surface I can look down and see the wheel moving freely with no force felt in the bars. So I'm thinking 2 or 3 bleed holes will control the front end dive a bit better without sacrificing comfort!
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Old 08-13-2018, 12:19 PM   #8
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ahh, didnt realize u could change the # of bleed holes. good stuff

in my experience, a bouncy ride on ripped surfaces is more often too little compression than too much, or even a rebound problem.
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Last edited by stangmx13; 08-13-2018 at 12:21 PM..
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Old 08-13-2018, 12:46 PM   #9
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This is why having a good pro set up your suspension is worth the money spent. Spring rates, preload, damping settings, oil level, oil weight, etc., etc., etc. is near impossible to figure out unless you do that kind of work all the time.

My recommendation is take it to a pro. Tell them what you've done and have them take a sag setting with you on the bike and all of your gear on. Then let them work their magic.

Oh, and rarely can you do one end of the bike and not do the other.
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Old 08-13-2018, 04:55 PM   #10
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I did take it to a pro.

BARF Garage pro's.

I have a pretty good understanding of suspension tuning, just trying to learn the last remaining aspects. I recently did the shock with a new damper and spring and it's feeling great!
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Old 08-13-2018, 08:34 PM   #11
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I would add another turn to the emulator spring. That helped the FXR a lot. The emulator spring is what balanced out the slow vs high speed damping for me. I also add a tsb. of STP to each fork leg to get the rebound adjusted with emulators.
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Old 08-16-2018, 01:43 PM   #12
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I would add another turn to the emulator spring. That helped the FXR a lot. The emulator spring is what balanced out the slow vs high speed damping for me. I also add a tsb. of STP to each fork leg to get the rebound adjusted with emulators.
I'm confused on the gold valves cause they say spring preload and spring rate is more for mid-to-high speed impacts, and the bleed holes are for low speed. But then they also say the spring preload is for brake dive.


Is brake dive a low, mid, or high speed event usually?
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Old 08-16-2018, 02:13 PM   #13
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brake dive is low to mid. it depends a lot on how hard u apply the brakes actually. and without a dyno chart for the forks and some cataloging, theres no way to know where your brake application falls in this whole situation.

how about some graphs:

heres what happens if u adjust preload


heres what happens if u adjust spring rate


the quadratic looking part at the beginning is the low-speed progressive portion of the curve, controlled by bleed size. the change from that to linear is called the "knee". the almost-linear portion is the high-speed section controlled by the "stack" or spring in your case. changing preload moves the knee up or down along the progressive curve at shown in the 1st graph. changing spring rate mostly changes the slope of the linear portion as shown in the 2nd graph. it could also change the knee location (it doesn't in this case)

so lets assume that your braking causes a max fork velocity (x-axis) thats double where the knee is in the 2nd graph. the knee location in the 2nd graph is equal to a preload setting of '1' in the 1st graph. with that setting and that fork velocity, u get damping about half from low-speed and half from high-speed damping. but if u crank up the preload to '5', notice that all your damping would be from low-speed and u get a TON more damping. even changing to '2' gives a bunch more damping because the linear portion is raised.

of course, that only works if the brake dive gets to my assumed fork velocity. if the velocity maxes only at the knee of the 2nd graph, a preload change won't do anything. ud need a bleed change.
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Last edited by stangmx13; 08-16-2018 at 02:16 PM..
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