[wakaba]

I currently have the stock showa adjustable fork on my 900Sie, but with my recent down, the right leg is all scraped up. No function issues, just looks like ass.

I found both a set of Showa TiN SBK legs which look like this

,

and a replacement stock 900sie leg at the junk yard.

Is the SBK fork that much better then my stock fork, and worth the efforts of milling out the upper tripple clamp?

 

[Norm]

The SBK forks are 43mm as opposed to your 41mm - that extra stiffness alone makes them much better. The ones pictured with the TIN coating, will also reduce stiction.

 

[wakaba]

are you talking about the stanction tubes being 43mm over the stock 41mm, or the tubes?

 

[kopfjager]

Monsters have 43mm

 

[Norm]

The slider tube. I'm not sure what year Monsters switched over from 41 to 43 (I pretty much live in the past), but just put a mic on the lower tube & you'll know.

 

[brad black]

the whole range went to 43 for '00 from memory.

the 748/926/996/998/999 sbk forks differ from all the other adjustable showa forks (851/888, ss, st, monster) by having the rebound bleed valves (what the adjusters adjust) down in the cartridge, while the others have it at the top of the fork just under the cap. so they have an advantage there in response, etc that you can't get with the other forks. however, it depends how switched on you are as to whether or not you'd actually feel it. i have bene told this also effects compression damping to soem extent, but i don't really understand how.

plus, if the shim stack is good (reworked) you really shouldn't need the adjusters open very much at all. one of the guys who used to work for us had a mate who does suspension for one of the top v8 supercar teams out here. they use ohlins in the cars and he was very surprised by the std fitment ohlins on ducatis having the adjusters open so far - 14 or so clicks is normal. in the race cars they pretty much run the adjusters closed, as they set up the shim stacks as required and go from there. he says maybe a click or two if it rains and they don't have time to change it, etc.

the adjusters are just bypass systems to let oil not go thru the shim stack. as such, they're a system prone to all the non linear flow issues you have with oil trying to move thru a fixed hole at varying speeds, just like the old style right side up forks. forks they don't use anymore because cartridge forks with internal shim stacks to control oil flow are much better.

if you paid someone money to have them set up the shim stack then there's no real reason to have to let oil bypass the stack. we run the adjusters on most showa forks around 8 to 12 clicks out - that's basically open to let as much oil as possible bypass the way too stiff shim stack. try winding your adjusters all the way in and ride it like that - and then try to think of a situation where that much damping is appropriate. i really don't get it.

sorry, i digressed a little. rant over.

 

[wakaba]

the whole range went to 43 for '00 from memory.

the 748/926/996/998/999 sbk forks differ from all the other adjustable showa forks (851/888, ss, st, monster) by having the rebound bleed valves (what the adjusters adjust) down in the cartridge, while the others have it at the top of the fork just under the cap. so they have an advantage there in response, etc that you can't get with the other forks. however, it depends how switched on you are as to whether or not you'd actually feel it. i have bene told this also effects compression damping to soem extent, but i don't really understand how.

plus, if the shim stack is good (reworked) you really shouldn't need the adjusters open very much at all. one of the guys who used to work for us had a mate who does suspension for one of the top v8 supercar teams out here. they use ohlins in the cars and he was very surprised by the std fitment ohlins on ducatis having the adjusters open so far - 14 or so clicks is normal. in the race cars they pretty much run the adjusters closed, as they set up the shim stacks as required and go from there. he says maybe a click or two if it rains and they don't have time to change it, etc.

the adjusters are just bypass systems to let oil not go thru the shim stack. as such, they're a system prone to all the non linear flow issues you have with oil trying to move thru a fixed hole at varying speeds, just like the old style right side up forks. forks they don't use anymore because cartridge forks with internal shim stacks to control oil flow are much better.

if you paid someone money to have them set up the shim stack then there's no real reason to have to let oil bypass the stack. we run the adjusters on most showa forks around 8 to 12 clicks out - that's basically open to let as much oil as possible bypass the way too stiff shim stack. try winding your adjusters all the way in and ride it like that - and then try to think of a situation where that much damping is appropriate. i really don't get it.

sorry, i digressed a little. rant over.

no issues with the rant, but I am a bit confused. Were you refering to the Ohlins vs. TiN showa?

I currently have the showa adjustable that are stock on the '02 M900ie, and the like. I have the option right now of the TiN fork, like pictured, and a stock '02 900ie leg to replace my damaged one. Becides the bling value, are the TiN forks that much better then my stockers?

 

[sonofthetis]

I was on the boards not too long ago looking for an answer to this. I finally got around to asking someone who made the made this swap and he basically said the forks recover faster from bumps and the tin lessens the friction. Maybe someone could put this into more technical language, but that's the general gist of it. It's a PITA to mill out your stock parts, but I think it would be worth trying out the new forks. You could always sell your 900 forks to recover some of your money.

 

[Guest]

TiN (Titanuim nitride) coating helps with what everyone calls "Stiction"


Basically stiction (short for Static Friction) causes the fork sliders to stick, ever so briefly, when the suspension first hits a bump.

It's caused by the contact between the fork seals and the fork sliders, and TiN apparently reduces it.

Not to threadjack, but what's the name of the black coating they're using more and more in place of TiN? I hear it's a lot more durable...

 

[Speeddog]

From the machine tool arena (endmills and such)...

TiCN, titanium carbo-nitride
TiAlN, titanium alumo-nitride

It may be one of those, IIRC the TiCN is nearly black.

 

[sonofthetis]

Not to threadjack, but what's the name of the black coating they're using more and more in place of TiN? I hear it's a lot more durable...

hard anodizing?

 

[Harry1160]

they actually feel like some kind of teflon coating.......

 

[brad black]

i was talking about showa forks, with reference to the ohlins, but it was general i guess. all shim stacks work on the same principle.

the black may be dlc - diamond like coating.

 

[Norm]

That's the term I always heard about the black coating - DLC.
Since we're already jacking this thread, does anyone know if 45mm USD fork are available without going SBK multi $$$$.

 

[Nuke_Boy]

On the SBK forks, moving the rebound adjuster out of the "piston rod" in the cartridge reduces the effect on compression damping that the rebound adjuster has when it is turned in and out. When the adjuster is in the end of the piston rod, oil flows through it at a high rate because of the pressure differential created in the cartridge. Moving the adjuster outside the cartridge reduces this effect.

The forks with the best cartridges out there right now are the GSXR series. They have the springs installed on top of the cartridge, rather than immersed in the fork oil. The springs being installed above the oil causes less drag in compression because of the friction between the oil and the spring. It also reduces the unsprung mass effect due to the spring location.

DLC coating (Diamond like Carbon) is the most durable of the low friction coatings out there. TIN coating is just as good. The most cost effective option to fight friction is to find a real good high pressure grease to put on your oil seals. The ohlins stuff is pretty good, it is the best I have used so far.

The interesting thing is that people think "stiction" is bad, and in excess it is. Only the ideal friction pattern of any front fork is to have high friction at low fork velocity, and low friction at high velocity. This in itself is unachievable, so that is where a compromise is made by everyone who makes suspension, trying to get the best feel with the lowest friction for high speed events.

And I agree 100% with brad black, if you get a good shim stack, you don't need adjusters at all. And most all adjusters are only good for the first full turn off of full closed. After that they don't do much at all. The ideal setup would be to have the adjusters set about 1 turn off the full seat, and then only turn them in if you feel the suspension fading due to excessive heat.

So to really answer the original question, the SBK forks are better than the 41mm forks. I think it is a good upgrade. Only a better one would be a set of gsxr1000 forks. Or just hold out and get a set of the new 1098 forks, as they are just as good.

 

[Guest]

[snipped]. Only a better one would be a set of gsxr1000 forks. [snipped]

GSXR Forks are about $300 on Ebay. At that price it's pretty hard for them to suck [cheeky]

I'm sorely tempted to get a pair and shim them so they'll fit my SBK sized triples. At that price you're getting fully adjustable, DLC coated and radial caliper ready forks. In short, a major bargain thanks to all the guys parting out GSXRs...

Here's the thread where TerraPete talks about what he did to get them on his bike...
http://www.ducatimonster.org/smf/in...ab423a7df2ff466e11b424f&topic=57284.msg703021

 

[brad black]

yeah, what nuke said.

could you just move the prelaod spacers to the bottom and the springs to the top?

 

[Nuke_Boy]

Brad,

The short answer is no.

The long answer is that you need the preload collar at the top to compress the spring / fork assembly in order to loosen the jam nuts that hold the piston (tension) rod to the top fork bolt. There are holes in the spring preload spacer that you use with a racetech or some other style tool to compress the spring for maintenance.

Even the cartridges that have the springs at the top have the ability to do this (spg collar on top). It is a key to being able to assemble / dissasemble the forks. Only the spring collar that is up there is very small.

 

[Speeddog]

On the SBK forks, moving the rebound adjuster out of the "piston rod" in the cartridge reduces the effect on compression damping that the rebound adjuster has when it is turned in and out. When the adjuster is in the end of the piston rod, oil flows through it at a high rate because of the pressure differential created in the cartridge. Moving the adjuster outside the cartridge reduces this effect.
--------------snip------------------

Nuke_boy, can you elaborate on that?

My understanding of your statement is that, among other things, adjustment of the rebound screw effects compression damping because the rebound and compression circuits aren't completely seperated.
It's been a long time since I had my Showas apart, so my memory of the layout is a little fuzzy.

The current shim stack in my RaceTech valved Showas is as follows:

3 of 0.15mm thick x 17mm diameter
1 of 0.10mm thick x 17mm diameter
1 of 0.10mm thick x 15mm diameter
1 of 0.10mm thick x 13mm diameter
1 of 0.10mm thick x 12mm diameter
1 of 0.10mm thick x 11mm diameter
1 of 0.10mm thick x 10mm diameter
1 of 0.10mm thick x 9mm diameter

How should I change that stack to get more low speed compression damping and less high speed damping?

And why?