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Set-up questions with DDC valves - static sag


faffi

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I have fitted a Nitron race shock and DDC valves to my fork. While fork dive is greatly diminished and the bike handles much more neutrally, the ride was harsh. Especially over square edged bumps. I know from experience that a poor fork (or shock) can make both ends feel bad, even if just one end is the real offender. 
 
Fitting the DDC valves was very easy. I dropped them in with a magnet and used the fork spring to retain them when withdrawing the magnet, noting where the spring sat. I then left the DDC valves in situ when I poured the oil in.
 
After gentle stroking to verify that the air was gone, I set the oil level to 142 mm with the valves in place. The instruction said to set the level at 150 mm - stock is 162 mm - but I couldn't find if that level should be set with or without the valves in place, so I set it a bit higher. I didn't cut the spacer, either, to accommodate for the length of the DDC valves, because I felt the extra preload could come in handy. And I can always cut them down later.
 
I went for a ride without checking sag (silly me) because the front end felt quite easy to compress at a standstill, bouncing it. The ride was very harsh, though, although very composed, so I decided to measure sag. Stiction gave values of between 3 and 5 mm, which I reckon is excellent, and static sag with bike alone measured between 9 and 12 mm. With me on top, it was between 24 and 29 mm, depending on whether I went from "the top" or "the bottom". Let's say a medium of 11 and 27, making that a difference of only 16 mm from my weight.
 
The way I understand this, sag with the bike is fairly OK, or perhaps a bit on the short side, but total sag is about 13 mm too little for a comfortable ride. To me, that suggest I need to lower oil level for a less progressive action.
 
Would you agree with that? If yes, what kind of oil level drop seems sensible to you in order to gain the desired extra sag?

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I'm still learning, but I'd try to get more sag with less preload or softer springs.

Craig Mapstone
Upstate New York

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The problem here is that the effect is too progressive due to too little air volume left by an oil level too high. The spring is correct, by the look of things. And reducing preload will not alter the spring - changing oil level will. If I reduce preload, the overall spring rate (with the effect from compressed air) will still be too high as the fork compress. But I have too little experience with this to know what effect the oil level have to springing. I can of course experiment, but if somebody know where to start, I may save myself several rounds of opening the forks :)

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Yah I'm still learning. Remove fluid to the recommended height might be good.
 
I have the Nitron r3 and ktech cartridges. My ride feels rough, but then I'm riding to work on crappy roads. Its a rough ride in my car, but not as noticable as you are sitting on a comfy seat. My sag is set at track levels, around 30mm, but I would like to try 38mm, but I am out of adjustment range. My rear spring is 625 lb per inch. Still have not checked what ktech sent me. I weigh 180 with gear.

Craig Mapstone
Upstate New York

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With that being said, the new suspension seems great with regard to handling. But damn, NY roads suck at times. I still need to get to the track for my first time.

Craig Mapstone
Upstate New York

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I am up to 220 lb with gear, 200 net. I listed 200-210 on the form and that my bike had been reduced in weight by 25 lb. The spring they delivered is listed as 675 in the spec sheet, and like you there is nothing more to back off - preload is at minimum. What is strange is that I get so much more sag than you despite a stronger spring - does your bike sag at all under its own weight? It does sound like the spring may be too soft with too much preload.
 
Sounds like your roads are like ours. This is commonplace on the roads I like to ride
 
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There are plenty of videos out there going into greater detail, but this is a very simple way to learn the basics of how to set up your suspension.  In another video, he also said that after 2-3000 miles the fork oil will have degenerated to a point where it will need changes to the setup - although our bikes do not have the possibility unless cartridges have been fitted.
 

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I have fitted a Nitron race shock and DDC valves to my fork. While fork dive is greatly diminished and the bike handles much more neutrally, the ride was harsh. Especially over square edged bumps. I know from experience that a poor fork (or shock) can make both ends feel bad, even if just one end is the real offender.  
Fitting the DDC valves was very easy. I dropped them in with a magnet and used the fork spring to retain them when withdrawing the magnet, noting where the spring sat. I then left the DDC valves in situ when I poured the oil in.
 
After gentle stroking to verify that the air was gone, I set the oil level to 142 mm with the valves in place. The instruction said to set the level at 150 mm - stock is 162 mm - but I couldn't find if that level should be set with or without the valves in place, so I set it a bit higher. I didn't cut the spacer, either, to accommodate for the length of the DDC valves, because I felt the extra preload could come in handy. And I can always cut them down later.
 
I went for a ride without checking sag (silly me) because the front end felt quite easy to compress at a standstill, bouncing it. The ride was very harsh, though, although very composed, so I decided to measure sag. Stiction gave values of between 3 and 5 mm, which I reckon is excellent, and static sag with bike alone measured between 9 and 12 mm. With me on top, it was between 24 and 29 mm, depending on whether I went from "the top" or "the bottom". Let's say a medium of 11 and 27, making that a difference of only 16 mm from my weight.
 
The way I understand this, sag with the bike is fairly OK, or perhaps a bit on the short side, but total sag is about 13 mm too little for a comfortable ride. To me, that suggest I need to lower oil level for a less progressive action.
 
Would you agree with that? If yes, what kind of oil level drop seems sensible to you in order to gain the desired extra sag?
 
 
I am about to order these ddc drop in emulator s. It seems to me you failed to follow any of the instructions either with oil level or spacer length.
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I am aware of that, and it was by choice. Also, the instructions weren't clear whether to set the oil level with or without the valves - they came back to me and said they would change that in their manual. Regardless, my choice of level cannot be far off; the valves would have upped the level by some amount as they have a lot of volume. Besides, I would always recommend setting the oil level with the valves in place because that's the only way you will know the actual running level (well, the springs will also reduce up the level slightly, but to a much lesser degree and all recommendations you will find take springs into account).
 
Regardless, I just learned that these settings are a rule of thumb for 41mm stanchions: Comfort 160 mm - Medium 150 mm - Hard 130 mm. Remember stock level is 162 mm for our bikes. Higher levels means higher internal pressure = more wear and greater chance of seal leaks plus more stiction. But also greater resistance towards bottoming. It's all about finding the best compromise for you.
 
I knew also that I probably would have to go back and play with the length of the preload spacer, but since it is easier to cut if you know by how much rather than learn that it ended up too short, that was the way I chose to do it. YMMV.
 
I will drop the oil level to 152 mm and re-measure what that does to sag - may be nothing, may be noticeable. That will be with the valves in place. I will then cut the spacers so that I end up with a total of 45 mm of sag with me sitting on the bike.

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Just to pester you with yet another video, from the 7-minute mark this will show you the effect of rider weight on the suspension

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I am aware of that, and it was by choice. Also, the instructions weren't clear whether to set the oil level with or without the valves - they came back to me and said they would change that in their manual. Regardless, my choice of level cannot be far off; the valves would have upped the level by some amount as they have a lot of volume. Besides, I would always recommend setting the oil level with the valves in place because that's the only way you will know the actual running level (well, the springs will also reduce up the level slightly, but to a much lesser degree and all recommendations you will find take springs into account). 
Regardless, I just learned that these settings are a rule of thumb for 41mm stanchions: Comfort 160 mm - Medium 150 mm - Hard 130 mm. Remember stock level is 162 mm for our bikes. Higher levels means higher internal pressure = more wear and greater chance of seal leaks plus more stiction. But also greater resistance towards bottoming. It's all about finding the best compromise for you.
 
I knew also that I probably would have to go back and play with the length of the preload spacer, but since it is easier to cut if you know by how much rather than learn that it ended up too short, that was the way I chose to do it. YMMV.
 
I will drop the oil level to 152 mm and re-measure what that does to sag - may be nothing, may be noticeable. That will be with the valves in place. I will then cut the spacers so that I end up with a total of 45 mm of sag with me sitting on the bike.
Then there should be no complaints, but maybe I mis-read your intended meaning. I'm going to use fork cap preload adjusters to give me the ability to dial in preload without having to take the fork caps out and cut spacers, I just have to subtract 10mm additional for the minimum setting on the adjusters on the spacers, and Todd is more than willing to send additional spacer material if you just ask. In fact he offered.
from Todd at Cogent:
"The adjustable fork caps are actually a very nice addition and they will have the advantage you mention.  I’ll need to send you enough spacer material for you to cut your own. (Remind me to send extra as it’s sometimes easy to miscalculate when you add an adjustable cap to the mix)."
 
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Yes, I have no complaints against Todd or Cogent - Todd has been really helpful - and of course adjustable preload caps would make things easier, no doubt. I just didn't think of it. Perhaps I will fit some later, but for now I think I will be fine by just cutting the stock spacers or get some PVC pipe and cut to size.

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Another interesting piece of information - preload should never exceed 15 mm according to this (and I have way more now)

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I've watched a ton of Dave moss videos, he has so much knowledge that you will find he often contradicts himself, simply because it depends what he is addressing to make a point, and in addition many of his videos are bike specific, race specific.
What it boils down to is every application is unique, and for lowly street use much of what he is saying is beyond what normal street riders will experience.

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