Re-valve M900sie forks, overkill for street riding?

[koko64]

My brother swapped out his forks from his 2001 M900S for a re-sprung and re-oiled set from a 2000 M900S. Picked them up for about $200 . Not sure exactly what work was done the forks but I was under the impression it was not a full re-valve or changeover of internals. The main thing was that the spring rate and oil weight/height were correct or at least close for his weight. We swapped out the forks and tested back to back and it was like night and day.

[clubhousemotorsports]

The 2000s has the same valve and springs stock as the 2001so if you noticed a big change they probably were not stock... yea!

  lol just read the 2000 had springs. Yes just the springs are going to be the biggest change I would guess 70% of the benefit  next 20% might be a compression valve (if needed). Last 10% is down to things like stiction (coatings,bushings etc) and fine tuning with valve design. This is where the price of high end parts comes into play if you need that last 10% then you need to spend the $$$ for better materials and designs.

Most of us don't need the last 10%......... doesn't mean we don't want it or shouldn't have it. I have ohlins on my monster street bike but my 748 and 750 trackbike both wear showa suspension I have reworked. I love the looks of the forks more than I have the ability to need the forks, and would rater crash on easily replaced forks.

which brings up another point the Ohlins parts are available to fix the ohlins parts (as are penske , works, showa and others) try getting a replacement parts for the Sachs or some of the Marzzocci

[TelemarkSean]

I'm going to go for the valves + springs.  Yeah, I don't need the final 10-15% performance factor. 

which brings up another point the Ohlins parts are available to fix the ohlins parts (as are penske , works, showa and others) try getting a replacement parts for the Sachs or some of the Marzzocci

I have a supposedly-unrebuildable Sachs shock on my Aprilia.  Not looking forward to the replacement cost for that guy.  Luckily the shock is in decent shape... for now.

[clubhousemotorsports]

The sachs shocks are a mixed blessing. I find them to be very well built with a very good valve inside (on the ducatis anyway). I often recommend them as a poor mans ohlins as they can be better in function than more expensive replacements with little work.

Now the down side is that many of the newer sach shocks do not have a schrader (nitrogen valve) on them. Some I can easily add one and it then is a shock that can be freshened and run for a long time just changing oil and nitrogen every 18k miles. BUT.
If you lose a shaft or damage components the shock is done, I have contacted Sachs about buying parts for their suspension and they didn't know they made the stuff. It appears it is a very small piece of a very large company that has little to no interest other than selling units to oem.

Yes we could have shafts and seals made but I feel to cost at this time would not be worth it as you suddenly get enough money into the shock  you would be best served buying a used penske or ohlins. On that note some times a ohlins or penske can be transformed. I have built ohlins shocks made for monsters into TT2 custom shocks and penske I have used R6 and rc51 shocks into ducati units for odd projects. Buy a close to what you need example used and then do the conversion.

[MonsterHPD]

Having looked through the most recent posts on this issue, I'd like to put in a few comments;

Thre are 2 distinctly different Showa fork designs; 1) the "long needle"which is what almost all cartridge forks are using; and 2) the "short needle" which is what all the 50/54 mm Showas except the SSie1000 are using.

The type 1) all work the same, and can be re-shimmed to whatever damping caracteristics you like.

The type 2) work totally differently, and can not be re-shimmed on the compression damping according to any type 1-based  experience; any compression damping pressure built up by compression of the forks will be leaked out through the rebound damping check valve, renering compression damping largely ineffective.

There are ways to improve this, but havinge realized these facts (after a lot of experimenting with the stock damping design), I simply gave up and I now convert any 50 / 54 fork I want to use seriously to the normal, "long needle" design.

This said,  I don't try to say this is the only way, but technically it's the easiest way out and in my view the most pragmatic since any commonly available cartridge fork knowledge will apply.  

If you don't want to do the "big" job, proper springs and attention to oil level and so on will make a big improvement, but damping performance will still be compromised, at the very least in terms of low-sped compresson damping adjustability, as well as in predictable response to different shim stack set-ups.

Basically, anything goes. Just don't leave it stock. Whatever you do, it will likely be an improvement.

             

[ducpainter]

I don't know which non adjustable Showa's I have on my 96 M900, but I can honestly say that the Race-Tech valves and springs made a huge difference.

Eric has been doing this on Ducs for a long time and he can make a set of forks not need adjusters. It will swallow up frost heaves and manhole covers like they aren't even there, and still be a fun ride on the track. I know it doesn't have a Race-Tech recommended stack.

Like several have said in this thread there are different ways to achieve results.

[clubhousemotorsports]

The difference is high speed vs low speed. Yes you may leak some low speed out with the short needle  in cap design but not so much it will matter for most people. We are not changing valves for the reasons of low speed damping as low speed has always been acceptable. we are working on making high speed (shaft speed) damping better.

Any oil bleeding out through the low speed (or rebound) circuit will be overcome and hydraulic lock with a high speed hit.  As I said before not all will need to change the high speed compression valving due to the roads/tracks they ride if you have high speed damping issues the valves certainly do help. Conversely if you have superbike forks with the long needle you already have good valves and aftermarket valves are mostly a color change.  This does not mean they do not improve with a stack re-shim just that the components are already good.  Damping requirements will be based on springs and conditions such as use and roads ridden.

The Arguably better design is also based on application. if you have ridden a streetfighter S with ohlins forks you know that having good forks do not necessarily make a good bike. The problem is not with the fork but with the chassis , too much rake = forks that try to flex more than slide. this is why you have to look at the whole package and talk to the customer to get the best for what they are looking for.

A race bike can be 180 degrees from a street bike in desired damping because a racer is looking for a different set of inputs than a road rider who simply wants a "good" ride.  Where a racer needs finer controls for more precise setup and detailed feedback these same feedback on rough roads can make for a harsher ride.

[koko64]

Your last paragraph perfectly describes my worked forks on my old 95 M900. Great handling on smooth roads or the track, but harsh on the rest of them!

[MonsterHPD]

Of course the main factor in having "good" suspension is in having a shim setup that matches the kind of riding you do and the feeling you want. The adjusters mainly moves the curves up and down.
A couple of years ago we did a test at reactive Suspension in York, Great Britain, on his crank-and-rod suspension tester. This setup can not reproduce sudden impacts, merely a sinusoidal movement, but it cn run speeds from 0.25 m/s to 1.3 m/s or so. I'm not sure where low speed ends and high speed starts, but running various set-ups at various adjuster position was still quite revealing. For the short-needle set-up, a couple of things were really apparent:

1) Compression damping force did not change much, regardless of speed within the interval mentioned; or approx. double. For comparison, my GSXR-cartridge Showa with compr / reb adjuster at 13 / 9 clicks was about 5:1;
2) Compression adjuster position makes hardly any difference at all, regardloess of speed;
3) The lay-out is a very efficient damping oil aerator; damping force reduces after a short while on the dyno;
4) Compression damping force is slightly higher with a closed rebound adjuster;
5) Rebound damping is pretty normal for the short needle Showa. Looks like the other forks, generally.

There was an article in the Feb 2014 Performance Bike magazine about this; I have a PDF if anyone's interested.

These results more or less verified what I already thought about these forks, and are one of the main reasons I don't bother with the short-needle forks anymore. They may be possible to improve significantly as described in this thread, without a complete re-design, but I rather do the whole thing and have a "normal" fork where I can put in a shimstack to my liking and have an idea what will happen.  

[clubhousemotorsports]

Keep in mind the clickers are LOW SPEED damping they are not high speed. Though the systems do overlap it would be like trying to fix a main jet problem with a pilot screw. Changing shim stacks will have little effect on the low speed damping circuit unless you have mostly closed low speed in which case the high speed would kick in sooner.

Moving the needle to the cartridge instead of at the top of the damper rod works better because it removes another potential leak point. The new point is still at the top of the cartridge so oil can still bleed by the shaft bushing on rebound. Better but not ... perfect if there is a thing.

I have not had a customer complain about lack of low speed compression, we are usually working to soften high speed compression and get enough low speed compression from the springs. Rebound is another matter, the stiffer springs do require more rebound so we do sometimes struggle to get where we desire to be depending how stiff the springs are. That said it only has happened on early 2000's 900 monsters with external adjustable forks. Other than those we do no even have issues.

[koko64]

With the correct spring and adjusted rebound valving, I figured the weak comp valving on the 2000-2001 forks was great for our shitty roads here.

[jerryz]

Monster HPD is absolutely right the short rebound needle 54mm forks are really crap ,, and need major mods to work , changing valves and springs are inneffective  on those horrors ,, I put some 996 forks and new valves and springs on my S4 now it is perfect..

[MonsterHPD]

Well, I suppose there are many ways to reaching the goal, and maybe you could say I took the easy way out by changing these forks to the same basic lay-out everyone else is using on this type of forks.

By doing so, I can use parts and experience (my own and from others) to get the results I'm after. Or at least try to. With the short-needle design, after a lot of work, and quite a bit of hard data, it's my conclusion they are not worth the effort. But it's my conclusion, and since I don't spend any more effort on them, I can't say there  might not be something I have not found.

As for high-speed and low-speed damping, it's clear that the adjuster just affects the low-speed damping area, and that by changing the settings you change the point where the shim stacks take over (in simplified terms).     

BTW, the people at Showa seem to be very concerned that no-one should be able to dial in too much compression damping; a lot of their compression pistons have a small hole drilled between the high-pressure and low-pressure sides of the piston; some others have a hole drilled in the cartridge rod where some pressure bleed-off can take place,and with the short-needle design no-one is ever going to dial in too much compression damping.  Are we talking litigation issues here? 

Returning to the original question of this thread, have these discussions helped .... ?   

[TelemarkSean]

BTW, the people at Showa seem to be very concerned that no-one should be able to dial in too much compression damping; a lot of their compression pistons have a small hole drilled between the high-pressure and low-pressure sides of the piston; some others have a hole drilled in the cartridge rod where some pressure bleed-off can take place,and with the short-needle design no-one is ever going to dial in too much compression damping.  Are we talking litigation issues here? 

Returning to the original question of this thread, have these discussions helped .... ?   

Yeah, I think this has been helpful.  I sent my forks off yesterday.  Should have them back in the bike in a week or so.