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Discussion Starter #21
I put the longer preload spacers into the forks and the noise is gone so it must have been the spring bouncing in the fork.

The forks had felt a bit harsh also so while I had them off the bike I changed the fork oil to Motorex Racing 5W (22.60 cSt) from Motul Factory Line Medium 10W (36 cSt) and the forks just soak up bumps now. I would have never figured that the oil viscosity would make such a difference. They’re like a whole different set of forks.
 

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When I get time I'll take some pictures of what I have and post them up for comment. I don't think it really matters either way how the spring is installed as long as nothing is rubbing and the fork is setup properly. What I did was have the lower stanchions from the S4 forks machined out to fit the compression adjuster from the 999 fork and I installed the 999 cartridge into the S4 fork tubes. I reassembled everything using the S4 spring and preload spacer and everything seems to fit ok but there was less preload on the spring because the 999 cartridge has more extension. I reinstalled the forks on my bike (a 2007 GT1000) and everything seems ok except I am getting a metallic clank from the forks on extension (like when dropping off the backside of a bump) and I was wondering if the spring is hitting the cartridge.
Hello,
just curious .... does the lost preload indicate that you have not compensated for the (potentially?) taller 999 cartridge / cartridge rod assembly? I.e., is the fork now taller?
 

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fuck me, 10 weight in those forks is just nuts. they'd be crappola grande. i usually use maxima 5 which is 16cst.

i had a set of ohlins from a 998s apart once that had been played with and one spring had no preload on it - forget how it actually was now. but the forks were full of aluminium slivers, and the oil was silver.
 

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Discussion Starter #24 (Edited)
fuck me, 10 weight in those forks is just nuts. they'd be crappola grande. i usually use maxima 5 which is 16cst.

i had a set of ohlins from a 998s apart once that had been played with and one spring had no preload on it - forget how it actually was now. but the forks were full of aluminium slivers, and the oil was silver.
I had initially used the Motul 10W as the viscosity was similar to the Showa SS8 (36.8 cSt) that is specified as the correct oil for the forks. I was thinking that lighter oil than the Motorex 5W might be even better so it’s interesting to see your comment about that. I initially thought that the lighter oil might be better because I’m using a 0.95kg/mm spring which is a little softer than the standard SBK spring but after doing some reading here in the forums I found that the harshness is a common complaint with the SBK forks and lighter oil is often used to combat this.
 

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Discussion Starter #25 (Edited)
Hello,
just curious .... does the lost preload indicate that you have not compensated for the (potentially?) taller 999 cartridge / cartridge rod assembly? I.e., is the fork now taller?
Yes, that’s exactly it. I did not account for the extra extension in the 999 cartridge when assembling the fork and there was a 13mm gap between the top of the preload/spring assembly and the top cap at full extension. I fitted a longer preload spacer to match the overall length of the preload/spring assembly from the 999 fork and everything is great now.

There is about 25mm of extra travel in the fork now. I looked at the tubes and where the bushings sit and I think there should be no issues because of this. The front of the bike sure rides wonderfully now. It just soaks up bumps and feels so stable and controlled.

It was mostly your Showa Blues post that led me down this path to modify the fork in the first place so thanks for doing that research and posting it up for everyone to see. I had initially purchased and installed the Monster S4 fork on my bike and couldn't figure out why I was having such a difficult time getting it dialed in. Then when I read about the rebound circuit issues in those forks it all started to make sense. Since I had the 999 forks already I decided to swap the internals instead of modifying the S4 cartridge and I couldn't be happier with the final result.
 

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the 999 manuals i have list donax ta or shell advance 7.5. the donax is allegedly 34 ish cst at 40, the advance 7.5 is 22 cst. so even their spec is pretty haphazard.
 

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Yes, that’s exactly it. I did not account for the extra extension in the 999 cartridge when assembling the fork and there was a 13mm gap between the top of the preload/spring assembly and the top cap at full extension. I fitted a longer preload spacer to match the overall length of the preload/spring assembly from the 999 fork and everything is great now.

There is about 25mm of extra travel in the fork now. I looked at the tubes and where the bushings sit and I think there should be no issues because of this. The front of the bike sure rides wonderfully now. It just soaks up bumps and feels so stable and controlled.

It was mostly your Showa Blues post that led me down this path to modify the fork in the first place so thanks for doing that research and posting it up for everyone to see. I had initially purchased and installed the Monster S4 fork on my bike and couldn't figure out why I was having such a difficult time getting it dialed in. Then when I read about the rebound circuit issues in those forks it all started to make sense. Since I had the 999 forks already I decided to swap the internals instead of modifying the S4 cartridge and I couldn't be happier with the final result.
OK, sounds like you are happy with the results. My only thought would be that by making the fork extend more, it will be les stable in due to the reduced overlap between inner and outer fork legs. It may not make much of a difference IRL, since you load the suspension down with vehicle and rider weight, but at least you should be aware and abservant on this.

The "7.5W" etc designation of suspension fluids are not not good indicators of viscosity, since there is no prescribed method to assign this number. I suppose it will tell you which oil is thicker than another from the same supplier, but they are not very good betwwen brands (as noted Belters post below). That´s one good reason to stick to the same brand of oil, and to check the cSt numbers, if available.
Personally, I mostly use 5W oil (Motul fully sythetic), since with cartridge forks (and shock absorbers) you use the shim setup to get the damping you want (or, as it happens, try to get ....).

I think maybe one major benefit of delving into the suspension like you have done is that it gives a much better understanding of how things work, what is possible and what is not, and a general desire to improve your bike as you go along. It´s no rocket science,, but it can be a lot of work :)
 

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Discussion Starter #28
OK, sounds like you are happy with the results. My only thought would be that by making the fork extend more, it will be les stable in due to the reduced overlap between inner and outer fork legs. It may not make much of a difference IRL, since you load the suspension down with vehicle and rider weight, but at least you should be aware and abservant on this.

The "7.5W" etc designation of suspension fluids are not not good indicators of viscosity, since there is no prescribed method to assign this number. I suppose it will tell you which oil is thicker than another from the same supplier, but they are not very good betwwen brands (as noted Belters post below). That´s one good reason to stick to the same brand of oil, and to check the cSt numbers, if available.
Personally, I mostly use 5W oil (Motul fully sythetic), since with cartridge forks (and shock absorbers) you use the shim setup to get the damping you want (or, as it happens, try to get ....).

I think maybe one major benefit of delving into the suspension like you have done is that it gives a much better understanding of how things work, what is possible and what is not, and a general desire to improve your bike as you go along. It´s no rocket science,, but it can be a lot of work :)
Any pointers on modifying the shim stacks? At higher speeds (90km/h +) the fork just swallows up almost any bump or road imperfection without any of it transferring back though to the bike. Between 50km/h and 80km/h when crossing expansion joints or hitting rough patches on the road I still get a good jolt through the bars (similar to how the high speed damping felt with the thicker fork oil) and also get quite a bit of dive under braking. I think it might be better with less high speed compression damping and more low speed damping or am I expecting too much from these forks? If I take one base shim off the compression stack is that a big step down in damping? I would love to change the valves but unfortunately it’s not in the budget right now. I am trying to improve them with the minimal cost outlay possible.
 

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This is a very difficult topic, and you have to remember that any fork (or shock) will have a certain amount of static friction that will have to be overcome before any movement happens.
With that said, assuming you have the stoc Showa pistons, there is n need to invest in an other fancy parts:

P4250083 by torbjörn bergström, on Flickr

This is the stock Showa piston, and a Gold Valve. The GW looks fancier, but I don´t think anyone would be able to tell the difference ..... so if this is what you have, it´s perfectly OK.

For road use, I like to use a cross-over shim; if you list the shim set-up you have, I could propose an alternative.

Finally, if you want to learn, I think that Racetechs "Suspension bible ....." book is a good introduction, as long as you remember the suspension world does not end north of Recatech :)
 

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Discussion Starter #30
This is a very difficult topic, and you have to remember that any fork (or shock) will have a certain amount of static friction that will have to be overcome before any movement happens.
With that said, assuming you have the stoc Showa pistons, there is n need to invest in an other fancy parts:

P4250083 by torbjörn bergström, on Flickr

This is the stock Showa piston, and a Gold Valve. The GW looks fancier, but I don´t think anyone would be able to tell the difference ..... so if this is what you have, it´s perfectly OK.

For road use, I like to use a cross-over shim; if you list the shim set-up you have, I could propose an alternative.

Finally, if you want to learn, I think that Racetechs "Suspension bible ....." book is a good introduction, as long as you remember the suspension world does not end north of Recatech :)
The valves looked stock when I had the forks apart before but I guess I have to open them up again and determine what the current shim setup is. Any tips on removing the bolt that holds the shim stack? Earlier you had noted to be careful with it as it breaks easily. Will I need to use some heat (from a heat gun) or is that a bad idea?
 

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Discussion Starter #32
i shot some video about these forks when i had a set apart recently, and just edited it up with some photos of the tool i made.

I had no idea you were Brad the Bike Boy. I have read all of your fork posts on your blog and they have been very helpful. Thank you for putting your work out there.

I made a very similar tool for holding the cartridge but mine is not nearly as pretty as yours is. I used a hand held grinder and a piece of old galvanized gas pipe I had in my toolbox that I used to use as a snipe. I should add a centering ring similar to what you did to make the tool easier to use as currently I have to be very careful that it doesn’t slip off the end of the cartridge.

Any tips on removing the nut that holds the valve and shim stack in place? Do I need to use some heat? I don’t want to break the valve body or do any damage
the valve or shims.
 

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Well, me neither :)

I have not had too many of these, but when I do, I heat it enough to soften the (potential) Loctite, then feel gently if the nut will loosen. If it does not, heat a little bit more, and feel again ... and when you´re all done, putting it back together, don´t give it that little extra twist on the wrench "just to make sure" ....

I have not broken one yet, so I have not had to try, but if you break it, I think it is possible to take away the whole alu post, and replace it with a drilled-out screw. A bit of work, but I think it would be possible.

I also think it is fun to make tools, and I have some that I don´t know what they are for anymore. So I´ve I got myself a Dremel engraving tool, making sure I mark any tool I make before I forget what it´s for. More urgent the older I get .... but I prefer that to the alternatives :)
 

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Discussion Starter #34 (Edited)
This is a very difficult topic, and you have to remember that any fork (or shock) will have a certain amount of static friction that will have to be overcome before any movement happens.
With that said, assuming you have the stoc Showa pistons, there is n need to invest in an other fancy parts:

P4250083 by torbjörn bergström, on Flickr

This is the stock Showa piston, and a Gold Valve. The GW looks fancier, but I don´t think anyone would be able to tell the difference ..... so if this is what you have, it´s perfectly OK.

For road use, I like to use a cross-over shim; if you list the shim set-up you have, I could propose an alternative.

Finally, if you want to learn, I think that Racetechs "Suspension bible ....." book is a good introduction, as long as you remember the suspension world does not end north of Recatech :)
I pulled the forks off and apart again today and here is the existing compression shim stack:

valve
11 - 0.15 x 17
1 - 0.2 x 10
3 - 0.4 x 11

The springs are 0.95kg/mm and I weigh 114kg in gear. I am getting 40mm of rider sag and 23mm of static sag with 8mm of preload. Total available fork travel is 158mm. I get about 6mm of stiction. I had the oil level set at 120mm and my zip tie on the fork was still about 35mm from bottoming. I am looking for a compliant ride for the street. The fork oil that is going back in is Motul Factory Line 5W (18 cSt).
 

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Good morning,

The 0.4 x 11 are just washers, partly to adjust the hieght of the stack (?), partly to provide a hard base tor the stack against the alu valve holder (?). I´m not sure, really.
The 0.2c10´s are the clamp shim, which dtermines the solid "post" of the stack and has a huge influene o the stiffness of the stack. Most Showas with a 10 mm cartridge rod uses a 9 mm clamp shim, either 2x0.2 or 1x0.3 mm.
The 11 pcs. of 0.15x17 mm shims are pretty normal fora Showa, maybe on the stiff side.

I am in no way an expert on this, and most of my experimenting has been on my Öhlins forks since they are much easier to work on (cartridge go out the top with the forks on the bike, and (most) of the oil remain in the forks).

For what it´s worth, I would try the following (if you want it softer):
1) 9 mm clamp. This will make the whole set-up softer, but will not really changfe the nature of the shim stack;
2) Try a cross-over shim below the first 0.15x17 (aka face shim), 0.10 mm thick and maybe 11 or 12 mm diameter. This will allow the face shim to bend slightly before the rest of the stack comes into play and will provide some softer initial action. It is possible to play with the position and diameter of the cross-over shim. If you should want to try a thicker cross-over shim, use several (I would say max 2, actually), since 2x0.10 is softer than 1x 0.15, and much softer than a 0.20 which would add to the general stiffness of the stack.
3) Remove a 0.15x17 or two. I´m not sure you would notice much difference unless you remove several, and that might then be too much ..... don´t know, really.
4) As a guide for option 3), use the Raceteh system (as discussed earlier, I think), to determine how many 0.15x17 shims you should use on top of the smaller shims in their tapered stack. The Showa big-port piston is similiar enough to the Gold Valve for this to be a reasonably good guide.

Be very careful with any Loctite if you use that on the valve holder nut, and clean the threads thoroughly of any old Loctite .... :)

Kind regards,,
Torbjörn.
 

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good that you're playing with it, will be interesting to see how you find it. torbjorn is quite experienced at this.

158mm is a lot of travel. are these meant to have a plastic travel limiter or the like that has been removed. i would have expected 125mm or so.

i find the centring ring on a tool like the one i made usually makes a massive difference to the overall strength and success of the tool. ie, nut fucking shit.
 

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The extra travel is due to the fact that the 999 cartridge + rod combo is 637 mm long fully extended, the Monster combo is 604 mm, which would match pretty well with the difference in travel (assuming that the cartridge does not bottom out, I have not checked that).
Personally, I would be a little concerned about the reduced overlap between inner and outer fork leg, but as long as the fork is loaded down to a sensible woking length maybe it does not matter that much ....
The 999 was (I think) the first bike to have the alu cartridge tube and rod, and they did not have any hydraulic travel stops on the rod. Neither did the later pre-999/949 with the steel cartridge tube + rod, but I´m not sure which oned did, and which ones did not have.
 

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Discussion Starter #38
The 999 cartridge has more travel in both compression and extension than the monster cartridge so there are no issues with bottoming out, the inner fork tube hits the fork cap first.

Thanks for the advice on the shim stack. I’ll track down some shims and let you know how it goes.
 
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