[bmadau]

Right, well since I've been comprehensively smacked down on that front, I'm going to fall back on my original point and say I still think "conventional" SPV shocks, where the CV is a "normally closed" valve, are fundamentally flawed for DH purposes, because the CV as it stands creates unnecessary extra "stiction" (there's your favourite word again )

And again, maybe you can make the shock work well with mods, but if it doesn't do it out of the box then I'm just not that interested.

One thing I am interested in though, is why you think the shaft displacement fluid is less well controlled through fox's boost valve than that passing through a main piston CV?

I know you are trying to get to me with referring to the low speed damping as sticktion by the way... I blame mostly Manitou for the misconceptions about the control valve by calling that stupid thing the Stable Platform Valve. All anyone thinks of when talking about the control valve is the "platform".

It had its place in the market back when it was introduced, but then the market changed and the shock didn't, so that's why it died. You are not the only one that thinks platform doesn't belong, not only on a DH bike, but just about any bike for that matter. I even agree with you to some degree on that front. I'll never say that it's perfect, it has it's inherent design characteristics, some of which are less desirable. My biggest gripe is the lack of mid stroke / speed damping, which is only emphasized worse on the 5th air and vpp type bikes with "smiley face" leverage ratio curves...

Metering shaft displacement oil is less effective because you are metering a smaller flow rate of oil, if that makes any sense. The cross section of a 1/2" shaft is only .196 in^2. The cross section of the face of the main piston is just under 1 in^2. You have a greater effective area, and greater oil displacement (flow though the ports) on a larger piston, giving you greater control.

I have lots of ideas for future incarnations of CV/t shocks that I hope to soon get to build. One of the biggest cons to the control valve is that it makes for a tall piston stack height assembly, so it can be a challenge to fit it in rear shocks where dead length is an issue.

BM

 

[Steve M]

Fair call about the oil displacements, but how hard is it to compensate for that by simply reducing the size of the CV ports?

 

[dhkid]

just had an idea, a cv valve with a bleed port. in a double barrel type configuration.

 

[Fly]

And again, maybe you can make the shock work well with mods, but if it doesn't do it out of the box then I'm just not that interested.

Haha S., no one is trying to get you interested in buying the shock or otherwise! Check out what I said before: I'm not trying to argue that 5th's should replace something that functions as well as a DHX if that's what you already have, but rather offering a few quick and easy solutions to bring them up to an acceptable level of performance without having to outlay close to $700 replacing them.

 

[bmadau]

Fair call about the oil displacements, but how hard is it to compensate for that by simply reducing the size of the CV ports?

You can, but the pressures would end up a lot higher, and you'd generate a lot more heat. You would have a much harder time making subtle adjustments also.

For fun, here are a few dyno graphs.

This fist one is the low speed of a Fox AVA and RP3. You see the AVA has next to no compression damping, it doesn't change much at higher speeds. This is a "light" tune RP3, and it's shown in all three propedal settings. As you can see, there's next to no difference between propedal mid and max.

Here's the RP3 force vs. displacement graph. The slope you see is from the gas force. Each line represents on velocity, 5, 10 & 20 in/sec. You can see there's very little "spread" as the velocity increases.

Here's a 5th air, low speed force vs. velocity. This is at 100psi, I'm sorry I don't have any graphs at other pressures... Maybe I have one source that can still from which I may still be able to aquire the files).

Here's where it gets interesting. 5th air force vs. displacement. Note how much the damping rises (we call it ramping) at the end of the stroke. Also, note that there's more spread at the end of the stroke than at the beginning. The 5th coil has much more spread than this, due to the compression head piston (valve, really) and speed sensitive compression adjusters.

I'm an XC rider, so I didn't think to take any DH shock graphs with me when I left PSI. I'll see what I can find.

BM

 

[Steve M]

You can, but the pressures would end up a lot higher, and you'd generate a lot more heat. You would have a much harder time making subtle adjustments also.

For fun, here are a few dyno graphs.

This fist one is the low speed of a Fox AVA and RP3. You see the AVA has next to no compression damping, it doesn't change much at higher speeds. This is a "light" tune RP3, and it's shown in all three propedal settings. As you can see, there's next to no difference between propedal mid and max.

Here's the RP3 force vs. displacement graph. The slope you see is from the gas force. Each line represents on velocity, 5, 10 & 20 in/sec. You can see there's very little "spread" as the velocity increases.

Here's a 5th air, low speed force vs. velocity. This is at 100psi, I'm sorry I don't have any graphs at other pressures... Maybe I have one source that can still from which I may still be able to aquire the files).

Here's where it gets interesting. 5th air force vs. displacement. Note how much the damping rises (we call it ramping) at the end of the stroke. Also, note that there's more spread at the end of the stroke than at the beginning. The 5th coil has much more spread than this, due to the compression head piston (valve, really) and speed sensitive compression adjusters.

I'm an XC rider, so I didn't think to take any DH shock graphs with me when I left PSI. I'll see what I can find.

BM

I can see how the pressures would end up higher, but I don't really see how you'd end up generating more heat - the work done by the damper is defined as the amount of mechanical/kinetic energy converted to thermal energy and for any given damper curve that's gotta be about the same (though if fluid is not really being well recirculated between reservoir and main body then it might be more concentrated in one place, can't really see this being such a problem though). Anyway, fair enough that it might just be impractical, assuming you do want that much compression damping.

Interesting on one of those graphs that there's not zero force at zero displacement (the 5th air f-d graph), how's that work? Is it because of a miscalibration in displacement of the test equipment, or from the negative air spring or what?

 

[bmadau]

Interesting on one of those graphs that there's not zero force at zero displacement (the 5th air f-d graph), how's that work? Is it because of a miscalibration in displacement of the test equipment, or from the negative air spring or what?

No springs, just dampers. The f/v chart shows most accurately the low speed "nose". The CV doesn't have to displace very far at all to start flowing a little oil. I mean, anything more than zero and it'll flow oil (kind of like a shim stack in that regard). It's not like fox's inertia valve that needs to displace a set distance before it uncovers the flow port. The rounding you see on the f/d curves at the higher speeds is because the dyno can't go from 0 to 20 in/sec in 0 time. It takes a short distance to accelerate up to testing velocity, then holds the velocity for the duration of the sampling length, then decelerates to a stop. It's actually quite impressive. It's an electromagnetic dyno, linear motors basically, with wicked power. It could do a max force of 4000lbs, and a test at 70in/sec could be felt anywhere in the building. The first time they tired it was before it was bolted down and the thing went airborne, and broke a permanent magnet. Lesson learned! It's small, like a 2 foot square footprint, and about 6' tall. I think it only weighs a few hundred pounds...

BM

 

[Steve M]

hahaha, wicked... getting the dyno airborne on its own downwards momentum. Someone else mentioned that happening with a dyno (I think in one of the many Cane Creek threads), pretty insane. Still don't get why the force is zero at positive displacement though (top curve on the f-d diagram), or did the shock just not reach full extension on that test?

Also, just random curious question, did you use different sample rates or software or something for the F-D tests as the F-V tests? Cos the F-V curves are very "jerky" (looks like a slow sample rate with linear interpolation to me?) whereas the F-D curves are very smooth and even go to the extent of showing signal noise. I only ask cos I'm working as a benchtest engineer right now (with brake systems) and we have to do a lot of stuff with sample rate alterations and noise filtering.

Those Fox Brain shocks work like absolute arse btw... I used to work at a Specialized-only dealer, and when the rep brought in the brand spanking flagship 07 carbon Epic for us to test out, all I could think was "ten grand for a bike with suspension that doesn't actually work... fantastic". I didn't like the sticky feeling from SPV much, but those brains are another whole world of bad compliance.

 

[bmadau]

Oh, ok... Yeah, we never tested a shock to full extension or compression, just in case something slipped we left ourselves a cushion before anything would crash. On the f/d graphs at low speeds you can see signal noise. On the f/v graphs, you see the "steps" because those tests for example were run at .25 in/sec, .5 in/sec, 1 in/sec (the low speeds were to check for sticktion, sometimes we'd test down to 1/32 in/sec), etc. It plots the points and connects the dots. It may have a setting to smooth the curve, like excel, but I don't know how to turn it on. I wasn't the chief dyno guy, I just knew how to set it up and run tests, though I did manage to destroy a few shocks in the process! When I ran these tests we were already phasing out the mtb line, so I was on thin ice to begin with.

BM

 

[Marcolino]

guys,

what do you think of fusing a manitou metel r (shimmed) and a 3way coil (ifp pressure adjust) combining them to get a Metel R 3 way (except without spv) ?

this is because i want the abillity to tune it with shims, and with the air valve on the ifp side it would be nice.

i would use the everything from the metel except the bushing side, replacing it with the 3way, that has a air valve...

any opinions?

ps- i can´t use just the 3way, because the stroke is longer...

thanks in advance,

Marcolino

 

[MttyTee]

The air adjust won't do much anything on a shim shock, but other than that, go for it.

 

[Marcolino]

hum...but on the metel the preload on the ifp was so high that small bump was hard to achieve...

i let go some of the pressure and it started having small bump abilities.
but as it´s not a valve method it couldnt be easily tunned.

my idea is adding the valve and possibly add shims for maximum tuning.
my worry is about bleeding the shock...

 

[Marcolino]

mttytee and guys,

what would you do to tune the metel shock?

would it be better to adjust shims and maintain high pressure on the ifp?

 

[Hannu]

Don't know about Metel, but I believe that it has pretty much same damping system to Radium, and radium has a very weird preloaded shimstack. Purpose for this is to act as a somekind of platform, but actually it just makes shock feel very stiff and overdamped. If you get that metel shimmed right, it should actually be a very good shock. I have not personally opened Radium, but I have owned one with stock shimstack and later with modified one, and difference in pretty big.

 

[MttyTee]

mttytee and guys,

what would you do to tune the metel shock?

would it be better to adjust shims and maintain high pressure on the ifp?

I would, with out getting into a lot of detail there is a pressure balance that needs to be maintained inside of a shock. Think of this, if there were no IFP pressure then there would be no resultant pressure against the shims and they wouldn't open. All that would happen is the piston would act as a plunger and push oil into the resy creating a vacuum behind the piston. Now imagine how much force (shims) is needed to control a shock when it is compressed really fast and how much pressure (IFP) is needed to push those shims open.

So, yeah, keep the pressure "high" and tune the shims.

Also, keep in mind this is a completely different scenario to a shock that has a pressure sensitive valve instead of shims. CV/t, SPV.

 

[Steve M]

I would, with out getting into a lot of detail there is a pressure balance that needs to be maintained inside of a shock. Think of this, if there were no IFP pressure then there would be no resultant pressure against the shims and they wouldn't open. All that would happen is the piston would act as a plunger and push oil into the resy creating a vacuum behind the piston. Now imagine how much force (shims) is needed to control a shock when it is compressed really fast and how much pressure (IFP) is needed to push those shims open.

So, yeah, keep the pressure "high" and tune the shims.

Also, keep in mind this is a completely different scenario to a shock that has a pressure sensitive valve instead of shims. CV/t, SPV.

Unless you had a secondary damping mechanism between the IFP and the piston...

 

[MttyTee]

Unless you had a secondary damping mechanism between the IFP and the piston...

Correct, I left that out for the sake of a simplistic explanation.

 

[FoesDWLink]

hmmm interesting, I have de-SP Valved the Curnutt shock on my 07 DHS 2:1 and it has made such a difference.
I really had trouble getting used to the bike before, because of its 5th like, unacceptable small bump compliance, and the inconsistancy of the rebound control. I had it for around a month riding 4 hour a day 5 days a week, so gave it plenty of time to bed in but still felt knotchy and sticky and shyite.

The Curnutt is just a 5th but looks like it relies on oil flow to shut the SPV valve instead of air pressure (correct me if i am wrong). Sometimes the valve would forget to shut after compressing and would stay open and rebound really fast on big bumps. It would happen only occasionally but was enough not to be able to trust the back end 100%. Maybe twice a run.

Also it would skip out really easily over small frequency bumps like off camber tree roots and braking bumps because, basically the shock wasn't working.
I had a Giant Glory (DHX5) before it and the Glory felt way better in the initial part of the travel and hugged the roots better (same track) but compared to the Foes it does get a bit wobbly under full compression and big hits, something the Foes was completely opposite to.

So after trying a few simple fixes like silicon lubing the SPV's o rings and fitting a spring to the piston,I set out to fix it... once and for all.
I pulled the shock apart and figured out how it all worked, quite similar to a 5th or Manitou but uses oil flow to shut the valve off. I decided the original piston and SPV valve had to go and made some measurement and started up the lathe.

I machined the piston from a 89 KTM 125 Ohlins shock piston, which was almost a perfect match (we found a complete bike at the recyclers and got the shock for $5!) to fit on the original Curnutt shaft. Compression stacks were used from it too . I used the original Curnutt rebound assembly, along with a few other little tweaks.
When the shock was rebuilt I used 5wt oil and 5 compression shims.

With the SPVed shock I run a 100lb spring and get about 3 inches of sag from it. When I initally sat on the bike with the deSPVed shock and 80psi in the air chamber it almost bottomed out just by sitting on it. This showed how much compression dampening the o ring and the SPV valve was causing.
I stripped it down again added 10wt oil and another 3 shim stacks and 100psi. This still gave me just under half sag so I had to order another spring from Foes, a 125lb spring.

With the 125lb spring, 10wt and 8 shim stacks and 100psi in the chamber, the bike has around 2.5 of sag and feels like what can be only described as a motocross bike. The shock is quite firm but has no noticable typically notchy pedaling platform and the bike feels and rides so much crisper and controlled than standard.

The bike tracks much better over the same tree roots and soaks them up so you cant feel them, insted of skittering sideways over them. The back end is so smooth and quiet, no annoying Curnutt clunking noise, just a nice sucking noise on rebound, much like a DHX.
The shock is actually working like a shock now and I have not had any inconsistant rebound kick back that the old shock used to have. Big hits compliance is identical. My feet dont blow off the pedals anymore and the bike still pedals really well which I am sure it would anyway due to pivot placement.

SPV valves were a fad a few years ago, everyone wanted them but, time has proven they don't actually work and a properly valved shim stack cant be beat.

 

[MttyTee]

SPV valves were a fad a few years ago, everyone wanted them but, time has proven they don't actually work and a properly valved shim stack cant be beat.

... MAN!! where have you been all my life!? I feel like such an IDIOT! I've wasted the last couple years of my life using precision machinery such as dyno's and data acquisition systems to develop my opinions of CV/t and other pneumatic valved dampers vs other styles and in the span of a month you figured it all out by "seat of the pants" riding!

Sorry to give you a hard time but when you make such an absolute statement like that your kind of asking for it. There are a few different configurations of damping available, each with their own strong and weak points... and each with the capability of performing at an extremely high level.

 

[k2-man]

Hello,

I currently have some issues with my 5th element demper.
On a given time (didn't do anything special); all oil flew out of the shock via de rebound button, and there was suddenly no rebound left anymore. (I think the rebound was blown)
When trying to dismantle the shock, I do not understand how to remove the internal floating piston? Can anyone give me a tip how to remove it.
I would like to refill my shock with fresh oil; and hope the rebound will be back.
Is it known for these type of schocks they can suddenly loose rebound ? and what could be a solution? is it a good idea to refill it ?

 

[MttyTee]

"Blown" is a very vague term.
Low or no pressure can make a CV/t damper feel like it has no rebound. Also, since the rebound needle is held against the rebound adjuster with pressure, lack of enough pressure can allow someone to thread the rebound adjuster to thread too far out and oil to leak past the o'ring.

You should be fine with an oil change.
Plunge the main body and the IFP will pop out
Check to make sure here is no oil inside the control valve, if so you should replace those o'rings.
Reassemble and ride!

 

[k2-man]

Thanks for your reply,
But when plunging the main shaft with the piston into the reservoir, a little bit of oil is pressured out past the edge, so i cannot put pressure on it to push the IFP out. I noticed a copper sealing around it, could it be that this one has been worn out?

 

[Sov]

^Do you have an air compressor? You can pop out the IFP by blasting air into the main body to pressurise it (point it away from your eyes!)

Might be a good idea to replace the rebound needle o-ring while you've got it apart. It's a standard 007 o-ring (70-75 duro i think)

 

[k2-man]

Hey Sov,

I had already the same idea !
But the O-ring you mention looks still very good, I thinkg the rebound was adjusted too far out.

 

[k2-man]

again a reply,

to make the rebound faster should I remove 1 shim on both sides of the valve?
The rebound is on the fastest setting still too slow for me.
How for should the IFP placed back in, is it a correct setting to place it 1 inch deep in relation to the top?

many thanks

 

[-Danno-]

again a reply,

to make the rebound faster should I remove 1 shim on both sides of the valve?
The rebound is on the fastest setting still too slow for me.
How for should the IFP placed back in, is it a correct setting to place it 1 inch deep in relation to the top?

many thanks

Check out this thread http://www.ridemonkey.com/forums/showthread.php?t=184201

 

[MttyTee]

again a reply,

to make the rebound faster should I remove 1 shim on both sides of the valve?
The rebound is on the fastest setting still too slow for me.
How for should the IFP placed back in, is it a correct setting to place it 1 inch deep in relation to the top?

many thanks

Without access to other shims you could remove 1-2 of the big shims that sits against the main piston. As far as the rebuild goes check the link Danno left, lots of good info. Hint:rebuild the shock bottomed out

 

[k2-man]

Hello,
I would like to thank you all for the advice !
I figured out i need some o-rings and he is back in business.

 

[mattmatt86]

Can anyone confirm if this mod will work on a Swinger 4-way Air? The rear shock on my slalom bike feels like poo.

 

[Kyle_rg]

Hey guys, I posted a full tutorial on how to do this to your shock on my new site. You can find it here:

Manitou/5th Shim Damper Mod

Use the contact page to get ahold of me if you have any questions, I'll get back to ya quick.

And to Matt, yes you can do this to your Swinger air. We are working on a kit for it as well. Should be ready soon.

 

[kebarb]

The Happymtb link does not work.

You need a shim or two on the piston side where the SPV valve was. I think that is where you are pointing to but you drew so much red, that I cannot see what is under there.

The shims act like a one way flap valve. WIthout any shims on that side, the oil can bypass the rebound shims and go right through the piston.

Hello guys, sorry havent been here since i left that URL to happy. The pictorial on this URL shows only how to do i, and if you can read the text (wich most of you cant) it says that the shims are NOT in the picture.

So you really NEED the shimstack, this is just how to dismantle and whre to put the shims and what to use as a spacer..

I will now read rest of the thread ;-)

 

[kebarb]

I took apart the SPV valve in my swinger, and I used the inner part of it as a spacer, as shown in your last picture

My question is, did you use 5wt oil in your shock?
'cause I used 2,5wt, and there is no rebound in my shock
Will it be okay with 5wt oil?

in addition, I changed the o-ring (which keeps the oil inside) to a softer one, so the shock is now as plush as a dhx, but has no rebound yet...i guess it's because the oil...

thanks
conor

In my opinion (and i am not very experienced) the oil should NOT be changed very much from original oil viscosity. the valving in the shock are designed around a special characteristic of the oil and you can cause problems if this changes. Cavitation and such.

If you like to experiment that is fine, but make sure to take notice if you feel sudden lockout in high speed bumps and such. Maybe also other strange behaviour might appear.

 

[FarkinRyan]

When I rebuilt my 5th the second time I stepped down to 2.5wt oil and the performance was much improved. This was on an Ironhorse 7point with a low leverage ratio to start with and an equally low spring weight because I'm a bit of a lightweight. With the standard oil I could never get it to rebound fast enough, with 2.5wt there was a much more usable range of rebound and I could get it set exactly how I liked it.

I never noticed any adverse performance as a result of this, only improvements.

 

[kebarb]

As long as it works well its a good tune, its just specualtion from my side. But i think it would be better to change shimstack and keep with stock oil. from 5 to 2.5 is not a very big change, but ive seen some ppl going from 10 to 2.5 and i think you might affect other characteristics then just the ones intended.

I see lots of lightweight riders (like myself) going for 2.5 in swingers / 5th.

Probably the problem occurs becaus the lower springrate doesnt allow for fast enough rebound. Maybe more preaload could also help this out. in the short range.

 

[FarkinRyan]

Probably the problem occurs becaus the lower springrate doesnt allow for fast enough rebound. Maybe more preaload could also help this out. in the short range.

That's just cutting off your nose to spite your face. Yes, the issue is that a low leverage ratio coupled with the light spring that such a design requires for a light rider means that there's not enough force on the shock to get it rebounding fast enough.

The point of running such a light spring though, is to get the correct sag for your weight, why you'd do that, then add preload is beyond me. Just get the shock tuned properly for your weight.

 

[miuan]

I've had the oil changed for a 2wt Oehlins in my 5th for the same reason that Ryan mentioned. My 7point still doesn't rebound as fast as it should. I have the same issue on a Roco equipped Izimu. Both 350 springs with little preload.

 

[dhkid]

i am able to get the rebound on my 5th really fast, best thing to do is reshim the rebound circuit.

right now its (from bottom to top) 2x small shims, 1x big shim, 1x small shim, 2x big shim. i know really technical, but hopefully it helps. its for a really low leverage design bike, so i wont recommend it for everyone.

if you just want to speed your rebound up a bit, do the sunday tune. thats 1x small shim, 1x big shim, 1x small shim, 2x big shim. (stock shim stack is 3x big shim and 3x small shim behind that.)

 

[mrpercussive]

i attempted doing this mod to my 6 way and it killed the rebound damping... tops out every time. What did i do wrong?

 

[samanderson4]

I think the best way is to buy a Fox.

 

[-Danno-]

i attempted doing this mod to my 6 way and it killed the rebound damping... tops out every time. What did i do wrong?

You've got to make sure that the compression holes on the piston are blocked off when it's rebounding or the oil will blow right through them causing top out. If the shims you put in there are too small diameter or they aren't against the piston/valve those holes will be open.