Suspension Examination:
- Thread starter n_green
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Jakobi
Super Moderator
I don't think there is any difference in pistons. Just the spring lengths. I didn't measure the length from the cap down either.
The piston purges the oil through the center and when bled will sit in the same position regardless of the spring. If the spring is too short, as in the case of Natos (-3mm) then the rod won't extend all the way back on its own. Pulling the leg out will still pull the piston down into the lowest position.
Ah sorry I meant springs not pistons. What I was trying to say is even through the ics piston always sits at the same height, obviously the longer 107mm spring will have more (potentially 7mm more) preload on it. Or does the 107mm have 0mm preload and the shorter 100mm spring have negative preload??
Jakobi
Super Moderator
The preload varies by spring length and PFP setting. I don't know if they have any other variances in terms of the actual shaft length either. Minor variances can occur depending on how the loc nut for the comp clicker is positioned, however even between several clicks its not a lot of difference in length.
Basically, when the rod is bottomed into the cart it displaces a set volume of oil. This oil then displaces the floating piston (IFP). When the cart is over filled for bleeing the volume pushes the piston up high enough that it slides over the cutway/taper in the rod and purges air and oil through the center of the IFP past the clearance of the seal.
So once bled, with the rod fully compressed, the piston will sit with the seal at the edge of the taper on the ICS shaft. This should be the same for all, with some variation for poor bleeds as the air is compressable. At this stage the ICS spring is pushing back against the IFP on the oil. It forces the IFP back down, extending the rod. If the spring has negative preload it won't extend all the way.
You could mathematically calculate the position of the IFP at full extension quite easily by working backwards.
So in short, yes the length of the spring has a profound change on preload. The PFP runs over a range of about 10mm (say 1mm a turn). So in theory, with all things the same, If my spring is 107mm and yours 100mm, you running your PFP at 7 turns in would be similar to mine at 0. A bloody big difference.
Glenn did the calcs at some point (which I also need to do), but he advised that with a spring that holds the piston against the stop, that the ICS would compress 7mm just through assembley. My piston floats around 6-7mm from the stop, so I would have a little preload once assembled. Working backwards I think Natos worked out to be -3mm (and I wound on a few turns of PFP).
All of this number crunching has me questioning the length of my spring again though and wanting to do more testing.
Green, with your ICS assembly standing piston side down, slide the IFP and ICS down towards the valve stack. Where is the spring in relation to the cap? Mine will sit with the edge of the spring just below where I can slightly preload it and push it aside. Natos floated around in there I think. I also notice some variance from one side to the other. My guess is that even stock, the springs are all over the shop.
Basically, when the rod is bottomed into the cart it displaces a set volume of oil. This oil then displaces the floating piston (IFP). When the cart is over filled for bleeing the volume pushes the piston up high enough that it slides over the cutway/taper in the rod and purges air and oil through the center of the IFP past the clearance of the seal.
So once bled, with the rod fully compressed, the piston will sit with the seal at the edge of the taper on the ICS shaft. This should be the same for all, with some variation for poor bleeds as the air is compressable. At this stage the ICS spring is pushing back against the IFP on the oil. It forces the IFP back down, extending the rod. If the spring has negative preload it won't extend all the way.
You could mathematically calculate the position of the IFP at full extension quite easily by working backwards.
So in short, yes the length of the spring has a profound change on preload. The PFP runs over a range of about 10mm (say 1mm a turn). So in theory, with all things the same, If my spring is 107mm and yours 100mm, you running your PFP at 7 turns in would be similar to mine at 0. A bloody big difference.
Glenn did the calcs at some point (which I also need to do), but he advised that with a spring that holds the piston against the stop, that the ICS would compress 7mm just through assembley. My piston floats around 6-7mm from the stop, so I would have a little preload once assembled. Working backwards I think Natos worked out to be -3mm (and I wound on a few turns of PFP).
All of this number crunching has me questioning the length of my spring again though and wanting to do more testing.
Green, with your ICS assembly standing piston side down, slide the IFP and ICS down towards the valve stack. Where is the spring in relation to the cap? Mine will sit with the edge of the spring just below where I can slightly preload it and push it aside. Natos floated around in there I think. I also notice some variance from one side to the other. My guess is that even stock, the springs are all over the shop.
Jakobi
Super Moderator
Really got me wondering what the length of my springs are now 
I checked the notes on Nathans and it definitely is 3-4mm difference in ours when measuring from the stop back to where the piston floats against the spring (when laid out on the bench) Exposed part of shaft below the piston.
I'm thinking I need to pull mine down again, but what would make sense is that Glenns were 107mm which would put them against the stop. Natos I wrote down the spring dimensions and am confident it was 100mm. So working off that mine would have to be 103mm. I also found some notes from the good man, Dave at STM Suspension who said he's measured a set around 102mm.
Like I said earlier, there seems to be some variance across the springs, which no doubt makes for some very interesting results across the board.
I checked the notes on Nathans and it definitely is 3-4mm difference in ours when measuring from the stop back to where the piston floats against the spring (when laid out on the bench) Exposed part of shaft below the piston.
I'm thinking I need to pull mine down again, but what would make sense is that Glenns were 107mm which would put them against the stop. Natos I wrote down the spring dimensions and am confident it was 100mm. So working off that mine would have to be 103mm. I also found some notes from the good man, Dave at STM Suspension who said he's measured a set around 102mm.
Like I said earlier, there seems to be some variance across the springs, which no doubt makes for some very interesting results across the board.
Hmm mine are back together now and I didn't pay particular attention to how much free play the spring had when the ifp was held down against the BV. But I estimate it would be 5-10mm max. Probably 5mm.
But my shaft does extend fully on its own so obviously there is some preload on the spring, even if it's 0mm. Dunno next time I have them apart I'll pay closer attention.
But my shaft does extend fully on its own so obviously there is some preload on the spring, even if it's 0mm. Dunno next time I have them apart I'll pay closer attention.
Ok interesting. Last weekend a 2 day ride i found them to be soft and felt low in the stroke just sitting there? I wound a full turn on the pfp after the first run and felt instantly better so I'm thinking i will go another 2 turns just for experimental reasons and see if that helps with the "soft settled" new springs. 2 turns is excessive i know but they are lighter springs than standard so shabby right 
Thanks for all the info in this thread guys its great.
Thanks for all the info in this thread guys its great.
Jakobi
Super Moderator
You'll notice 2 turns for sure, but in comparison mine at 0 turns is equivalent to yours at 3 and that without taking the lighter rate into account. I find around 1/4 turn has been working for me. Your base valve has also been setup firmer than mine. How many hours you racked up since you got them back? I serviced mine after yours, and have done mine again since. Found quite a bit of contamination in one of the legs. Didn't find any signs of damage/wear and had thorougly inspected, so put it down to the springs breaking in to a certain extent. Will be pulling them down in another 20hrs to inspect again. On another topic, I think my trail tech has been on the blink. It eats batterys, and I think stops reading at times (possibly over volting). As such the time I thought I put on them could be wrong. Ride before last which was a fat loop of around 80kms of singles only showed as 40kms on the taco. These things are shit and nothing but trouble!
The other thing to note with this, is that the purpose of the ICS spring is to keep pressure on the fluid to fight off cavitation. By having negative preload the initial action will be very soft, but also defeats the purpose of a closed chamber fork.
The other thing to note with this, is that the purpose of the ICS spring is to keep pressure on the fluid to fight off cavitation. By having negative preload the initial action will be very soft, but also defeats the purpose of a closed chamber fork.
Hence the reason it felt better with the extra turn. See how i go if i don't find it good enough i have the original springs still for pfp.I have only put 2 tanks of juice through unfortunately.
I agree with the trail tech mine went to the restart screen last ride so will throw a battery in to see if thats all it is.
I agree with the trail tech mine went to the restart screen last ride so will throw a battery in to see if thats all it is.
Simmo737
Gold Level Site Supporter
Another point of interest, Simmo have you measured your ics spring? Mine is a different length to Jakes (same length as Natos??).
Can't remember how that affects things though? Jake help a brother out?
Haven't measured it but I've got about 4mm play roughly
Went and rode the test track again today with the new suspension settings.
The first few laps were spent trying to dial in the rear shock, in the end surprisingly I ended up using almost the same clicker settings as what I did with the 6.0, although I'm further in with the LSC, running about 4-5 clicks out on LSC now, seems to offer the best balance of keeping it up in the stroke at the same time as allowing some squat to grip when needed. Rebond is the same as what I used with the 6.0, it's a very fine line at the moment between letting it rebound quick enough not to skip over the acceleration bumps on the track to then not pushing on off camber and slippery rocks. No doubt when I next ride a rock garden I'll wind the rebound in a few clicks...
Now the forks, my goal today was to dial in the clickers to where I was happiest with them, then play with the PFP to get a feel for it and see if I could use it to keep the forks up in the stroke whilst being able to wind off the comp clicker.
The rain storms interrupted my testing so I didn't get a chance to do much apart from get the clickers close. The new rebound stack worked well, the clickers are now at 10-11 out (they were at 1), and while I could add a click or two they are close.
The comp clicker is still pretty far in, about 4-5 now, any further in and it stays too high in the stroke and starts deflecting on trail trash. But they are pretty good where they are.
What is much improved is the forks blowing through the stroke and bottoming out, it still happens on the sections where it was doing it in the video that started this thread, but not as often and not as bad. Whether it was the extra shim or increasing the outer oil level to 350mm I don't know, but its better.
No video today as I was on my own, no camera man to film me
The first few laps were spent trying to dial in the rear shock, in the end surprisingly I ended up using almost the same clicker settings as what I did with the 6.0, although I'm further in with the LSC, running about 4-5 clicks out on LSC now, seems to offer the best balance of keeping it up in the stroke at the same time as allowing some squat to grip when needed. Rebond is the same as what I used with the 6.0, it's a very fine line at the moment between letting it rebound quick enough not to skip over the acceleration bumps on the track to then not pushing on off camber and slippery rocks. No doubt when I next ride a rock garden I'll wind the rebound in a few clicks...
Now the forks, my goal today was to dial in the clickers to where I was happiest with them, then play with the PFP to get a feel for it and see if I could use it to keep the forks up in the stroke whilst being able to wind off the comp clicker.
The rain storms interrupted my testing so I didn't get a chance to do much apart from get the clickers close. The new rebound stack worked well, the clickers are now at 10-11 out (they were at 1), and while I could add a click or two they are close.
The comp clicker is still pretty far in, about 4-5 now, any further in and it stays too high in the stroke and starts deflecting on trail trash. But they are pretty good where they are.
What is much improved is the forks blowing through the stroke and bottoming out, it still happens on the sections where it was doing it in the video that started this thread, but not as often and not as bad. Whether it was the extra shim or increasing the outer oil level to 350mm I don't know, but its better.
No video today as I was on my own, no camera man to film me
Yep it's nice now. It ramps up right where I wanted it to but doesn't get stiff or jar through the bars. I may still add a few clicks of rebound, didn't really need it as it wasn't climbing ruts if I was on my game but I like slower rebound up front, feels more settled to me. If I do it will only be a click or two.
What are your thoughts on pfp? Theoretical could you wind it in a few turns to firm up initial travel and hold t up in the stroke and would this allow less comp clickers??
Hmm more testing to go yet...
What are your thoughts on pfp? Theoretical could you wind it in a few turns to firm up initial travel and hold t up in the stroke and would this allow less comp clickers??
Hmm more testing to go yet...
Jakobi
Super Moderator
By increasing preload on ICS you are increasing the force required to set the IFP in motion. This is felt in the intial movement of the stroke. One the preload is overcome the spring rate is in effect. Same theory as a shock spring really. The purpose of the pressure spring is to reduce cavitation, the same way that the reservoir works on a shock.
The comp clicker is a bleed/bypass circuit which is active all the time, however based on its size it can only flow at a certain rate before its overhemed and the comp stack has to contribute/flex more.
So really, both effect low shaft speeds speed/smaller forces on the shock. The PFP is probably just a bit more position sensitive in that once the fork is half compressed the shaft displacement has already put a load of preload onto the spring regardless of where you have set the PFP.
The comp clicker is a bleed/bypass circuit which is active all the time, however based on its size it can only flow at a certain rate before its overhemed and the comp stack has to contribute/flex more.
So really, both effect low shaft speeds speed/smaller forces on the shock. The PFP is probably just a bit more position sensitive in that once the fork is half compressed the shaft displacement has already put a load of preload onto the spring regardless of where you have set the PFP.
Simmo737
Gold Level Site Supporter
Rode my bike for a proper ride yesterday (didn't get to ride down vicco) at cessnock. Super happy with the terry hay shock, totally settled the bike down , makes the front feel better too. Lots of grip, we'll needed at a vey wet cessnock yesterday. Combined with new jetting it was the end of fiddling for me I think. 
I spent two days riding at Dalmeny NSW in some prime terrain. Everything from super slow techy rocky climbs, off camber moss covered root infested trails, rocky creek beds, flowing 2nd/3rd gear bermed up single, twin trail with drainage jumps and 4inch to foot thick logs were encountered. My suspension was freaking unreal. It ate everything up. Sensational grip and plushness all weekend.
Still get a bit of a kick from the shock when going over bigger drainage humps but careful body position and throttle blip prevents this.
Not sure on clicker position, the shock rebound is roughly halfway out so that's good, LSC is roughly 5-7 out of 25.
Fork comp is roughly 5-7 out same as rebound so while I could hunt for perfection and shuffle shims to allow the clickers to settle at the halfway mark I don't think I'll bother.
Still get a bit of a kick from the shock when going over bigger drainage humps but careful body position and throttle blip prevents this.
Not sure on clicker position, the shock rebound is roughly halfway out so that's good, LSC is roughly 5-7 out of 25.
Fork comp is roughly 5-7 out same as rebound so while I could hunt for perfection and shuffle shims to allow the clickers to settle at the halfway mark I don't think I'll bother.
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