[Pembo6]

Thanks Arnea.

 

[Lucky Luciano]

Hello, new owner of a Marvel Comp here.
Am I right in my understanding than when the compression knob is fully open, shim stacks behave similar?

I'm looking mainly for small bump compliance, less for avoiding brake dive and even less for avoiding pedal bob. Do I still need a tuning if I leave the ABS at MAX-8 as in fully open?

 

[Dougal]

Hello, new owner of a Marvel Comp here.
Am I right in my understanding than when the compression knob is fully open, shim stacks behave similar?

I'm looking mainly for small bump compliance, less for avoiding brake dive and even less for avoiding pedal bob. Do I still need a tuning if I leave the ABS at MAX-8 as in fully open?

Fully open only controls the bypass around the shims which is quite small. Oil still transfers through the shims on all but the slowest movements. The softer the shim stack the more oil will flow through it.

 

[Pembo6]

I recently changed my Marvel shim stack from XC to teh Trail version. Pretty sure I removed both platform shims and I added a speed shim (18 OD x 0.2 thick). I weigh about 72kh without gear, and it made a significant difference. I have always run teh fork fully open. But now I get MUCHbetter small bump sensitivity. I thought I might blow through the travel muich faster but that hasnt been a problem. The suspension on big hits has remained unchanged. I highly recomend the changes. Also, I havent noticed any brake dive or pedal bobn. Ive got the 120mm version.

 

[Pembo6]

Forgot to mention. Be very careful with the torque when tightening the shim stack. Dont over tighten or you will buckly the shims. Only need the slightest bit of torque.

 

[tigris99]

On full open not much is going to change because the shim stack has little effect. I can't believe anyone would ride these full open as dive and Bob is impossible to deal with. But if your exceptionally light weight or used to a fork with a very bad damper, then it's possible I guess. I'm not a great rider or anything, but brake dive and Bob drove me nuts out of the box on anything more open than 5 clicks open. Felt like I was riding a bike with a Walmart fork that had rebound dampening at least.

Actually sounds more like you have your air pressure too high on the air spring. Marvel expert and pro versions have a negative spring which gives awesome small bump compliance to nce the fork has a few rides on it and you have your air pressure set correctly.



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[Lucky Luciano]

Sag is at about 25% so pressure should be OK. I'm gonna try it at sag 30% too, and I'm still in the break-in period (only ridden 5 hour on road).

I bought the Comp because nobody here or elsewhere could explain clearly how Expert/Pro would be better than the Comp, for 90 euros more.

 

[tigris99]

Ya I didn't see you ask that, I could have explained. And all the info is on manitou's website. The comp your not going to get the small bump compliance of better forks due to the air spring. TS air is a simple and basic air spring system. The expert and pro use ISO air which has a negative spring to give the complainace.

Expert vs pro I see no gain besides for the weight weenies. The damper is reduced to cartridge instead of full leg bath. Less fluid in the damper = lower weight. Though I do not know if expert is available all thru axle variants. I just know it comes in 15mm.

Comp version is limited and messing with the damper is going to do little (is it even abs+?). It will improve after some use. Reducing platform shims would help at speed if you want to close the damper more (so it's actually doing something).

Another thing that may help (we can do it with ISO air, not sure on TS air) is making the air spring more progressive by adding oil to the air spring (very small amounts) and running your pressure lower.

Sag is only a STARTING POINT. You adjust more or less depends on what you need. There is alot that can be tuned on manitou's forks, takes time and research to learn and understand how to adjust each thing.

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[mullen119]

Ya I didn't see you ask that, I could have explained. And all the info is on manitou's website. The comp your not going to get the small bump compliance of better forks due to the air spring. TS air is a simple and basic air spring system. The expert and pro use ISO air which has a negative spring to give the complainace.

Expert vs pro I see no gain besides for the weight weenies. The damper is reduced to cartridge instead of full leg bath. Less fluid in the damper = lower weight. Though I do not know if expert is available all thru axle variants. I just know it comes in 15mm.

Comp version is limited and messing with the damper is going to do little (is it even abs+?). It will improve after some use. Reducing platform shims would help at speed if you want to close the damper more (so it's actually doing something).

Another thing that may help (we can do it with ISO air, not sure on TS air) is making the air spring more progressive by adding oil to the air spring (very small amounts) and running your pressure lower.

Sag is only a STARTING POINT. You adjust more or less depends on what you need. There is alot that can be tuned on manitou's forks, takes time and research to learn and understand how to adjust each thing.

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Iso air and ts air are nearly identical spring systems. Both are positive air springs with negative coil springs. The only difference is that there is a soft, elastomer like bumper between the piston and push rod that helps the first few mm of travel be free of seal drag. One is not much different from the other performance wise.

Also, adding oil on the piston doesn't really work. The oil makes it past the quad ring very quickly. Manitou is no longer specing oil on the pistons in new forks, opting for a good coating of suspension grease (slicoleum/slick honey) instead. It just works better.

Definitely move away from the stock xc stack. It's far to stiff for normal riding. Trail stacks or even linear work much better, allowing you to dial in a proper lsc setting without a harsh feel

 

[tigris99]

I didn't know they got away from the oil, I'll have to remember that during my next fork service. I have a big tube of prep m so I'm covered there

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[mullen119]

I didn't know they got away from the oil, I'll have to remember that during my next fork service. I have a big tube of prep m so I'm covered there

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It just works better. It caused issues on the mattoc because the oil fairly quickly made its way to the negative chamber. The TS/iso air system don't show issues as quickly because of the negative coil, but after a few rides the piston is dry and performance suffers.

Prep m is decent, but fairly thin when temperatures get warm. That's why the switch to slicoleum. It tends to stay in place longer when being used as a primary lubricant.

 

[tigris99]

That's one thing i haven't seen yet as I opened my system several times during tuning. Being a big guy, they tune well but takes a little more time. Each change I would ride a few times.

Never had a dry air piston but between the last 2 changes I did notice 95% of the extra oil I had put in the air chamber was gone. Thought maybe I had forgot to put it back in (which I'm insanely meticulous so was surprised). But this would explain things, it just slowly worked it's way past into the bottom of the fork. Shocking oil makes it through but air doesnt (not at a noticeable rate anyway)

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[mullen119]

That's one thing i haven't seen yet as I opened my system several times during tuning. Being a big guy, they tune well but takes a little more time. Each change I would ride a few times.

Never had a dry air piston but between the last 2 changes I did notice 95% of the extra oil I had put in the air chamber was gone. Thought maybe I had forgot to put it back in (which I'm insanely meticulous so was surprised). But this would explain things, it just slowly worked it's way past into the bottom of the fork. Shocking oil makes it through but air doesnt (not at a noticeable rate anyway)

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The two rides I stated is for the few ml called for. More would last longer.

What happens is the oil clings to the walls and the seals slide past some of it rather than wiping it clean. On the rebound stroke, it pushes just a little bit down to the bottom, lost into the negative spring. Multiply that by thousands of stokes and it all disappears. You can solve it by having a lip on the quad ring to wipe the oil clean, but that adds friction.

 

[tigris99]

Ya I didn't even think about all that. I put extra in for changing progression but noticed on the last service (after a season) it was all gone, not dry but very little in there and after bike Sat for a bit, started seeing a bit of stiction. Never thought about the internal seal design.

Which I'm fine with that, I'll stuff some prep m in there on this service I'm about to do (well just change lower oil, clean/grease wipers, etc). Don't see a point right now with almost full tube of prep m to buy something different as I'm on a limited budget. Added a fat bike to my garage and it needs love too (bought used) after riding it hard and putting it away wet all season.

Thanks for the info there, I didn't know about that update. But too my Marvel's are going on season 3 technically with first 2 being short. Bought forks in August yr 1, last yr I was down for several months do to elbow injury followed by surgery to fix it. I still service it each year regardless. But since everything is like new, saw no need to check into anything. This year it'll probably see it a couple times.

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[mullen119]

Ya I didn't even think about all that. I put extra in for changing progression but noticed on the last service (after a season) it was all gone, not dry but very little in there and after bike Sat for a bit, started seeing a bit of stiction. Never thought about the internal seal design.

Which I'm fine with that, I'll stuff some prep m in there on this service I'm about to do (well just change lower oil, clean/grease wipers, etc). Don't see a point right now with almost full tube of prep m to buy something different as I'm on a limited budget. Added a fat bike to my garage and it needs love too (bought used) after riding it hard and putting it away wet all season.

Thanks for the info there, I didn't know about that update. But too my Marvel's are going on season 3 technically with first 2 being short. Bought forks in August yr 1, last yr I was down for several months do to elbow injury followed by surgery to fix it. I still service it each year regardless. But since everything is like new, saw no need to check into anything. This year it'll probably see it a couple times.

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:thumbsup: prep m works fine, I wouldn't worry about it. Just load it on and put a little on top the piston to work it's way down over time

 

[GrayJay]

I recently got a 100mm 29er Marvel comp and have been slowly reading through and digesting all the available ABS+ tuning info including the Manitou shim stack tuning guide.

Looking a bit further trying to research the effects of shim stack tuning, it pretty quickly became apparent that shock tuners from the motorcycle world have developed a deep understanding and knowledge of the the complex dynamics of shock tuning that would be potentially beneficial for a better understanding of out ABS+ manitous. One of the sources I came across was the commercial spreadsheet calculation program Shim ReStackor, Finally software to tune a shim stack
From the trial demo, the shimrestacker program looks to be very detailed but with a steep introductory learning curve and much of the preset options and documentation is geared more directly for motorcross shocks. I would be curious if anyone has ever successfully configured shimrestacker to analyze manitou fork ABS+ shim tuning or if there are any similar (but perhaps less complex) shim stack calculation programs available?

Short of trying to program an entire physics simulation calculator, it occurred to me that it might not be too difficult to input all the manitou factory ABS+ tuning guide info into a spreadsheet in order to help sort out some of the tuning options. The combine HSC + LSC dyno curves would be complicated to model but it should not be to difficult to calcualte the overall spring rate, pre-load tension and platform levels for some of the more basic tuning curves. Has anyone tried something similar ?

 

[arnea]

I'm not sure how one can model the ABS+ special piston with lip in the Shim Restackor. Actually tuning of the ABS+ is so fast and the number of reasonable combinations is not big - so the easiest (and most fun) way is just start experimenting.

First question is - do you need any preload at all? I recommend to check out linear stacks first. I ride cross country and use light linear stack with low speed needle almost closed - it has very good small bump sensitivity and good midstroke. I like to spin (no out of saddle sprints) and this stack fits me very well.

 

[tigris99]

OK Mullen, decided to do a full service. Trying something different too. First I did as advised, prep m in the air chamber.

Went linear stack (2 speed and 1 13mm to stiffen things up on are hard hit), 120mm with around 30% sag. Hopefully smooth things out while I keep my lsc half closed to keep dive/Bob where I like it.

@gray: advise, I did the sheets and all that, spent hours burning them into my brain. Outcome is I have no idea where the print offs are, could care less. Simple things to know.

Platform shim creates a "blow off" type effect. The biggest diameter ones. Unless you want it to have a platform for climbs, just leave them out. As I did now, too harsh for my liking as my climbs always have roots and crap.

Speed shims: these are your linear damping. More/thicker the stronger the effect. Useful info is that it takes (numbers are for reference, not actual thicknesses) 3 of a .01 thickness to equal 1 .02 thickness for damping effect.

13mm shims create a "second stage" to the linear. On small bumps the speed shims deal with it, when you have a bigger hit, the speed shims want to open all the way, but the 13mm shim (s) stiffen the speed shims after they open to a certain point. Increasing damping effect when you have a big hit to reduce bottom out.

May not be 100% correct way of explaining it but that's how I have it in my head. Shims are easy to swap around so why not give yourself more excuses to ride. Testing out fork tuning. Fancy graphs and curves give you a reference to understand how each shim size effects properties. Beyond that they are totally useless as outside temp, variations in rider weight and so on will change those curves.

LAB TESTS ARE ONLY FOR A REFERENCE AS A STARTING POINT, THEY ARE NOT REAL WORLD PERFORMANCE[emoji14]

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[arnea]

Useful info is that it takes (numbers are for reference, not actual thicknesses) 3 of a .01 thickness to equal 1 .02 thickness for damping effect.

I'm pretty sure that it takes about 8 .1 shims to have equal damping effect of 1 .2 shim. There is cubic relationship between thickness and stiffness of shims.

From Shim Restackor page (http://www.shimrestackor.com/Code/Sample_Applications/Demo_3Clk/3clk-softer.htm):

"Here, you could attempt to apply the typical shim stack rules of thumb: stack stiffness varies with the diameter squared and the thickness cubed"

 

[tigris99]

I specifically said "numbers for reference"

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