996-998 Fork springs: can anyone help??

[Connader]

Hi,
a few years ago, I started to build a 996 Racebike. I put on my Showa Fork, wich appeared to be an 99' SPS-Fork (the owner upgraded to Öhlins and sold it to me).
Now, on my first trackdays I realized bad turn-in behaviors and the zip-tie around the forkleg showed me about 4cm of unused travel. When I later changed the fork oil I put in 30ml less in each leg to have a bigger air-gap and the unused travel became less, like about 1,5-2Cm left, what was ok.

Now, I upgraded that racebike with my 998S engine and to have an authentic 998S, I also upgraded to the Showa TIN-forks. First I changed the oil again, because I didn't know how old the fork was and what it has seen. Again I put in 30ml less in each leg to get my good setup.

Yeterday I first test-rided the bike and it went awesome enginewise!! Also the brakes, now upgraded with an Brembo-radialpump was great. I honestly broke harder and later then ever before. I overtook a lot of guys on the brake, what didn't happen that often before, but this new brake is just awesome.
But however: turn in into a corner was bad. I wasn't used to that, my old 996 just did this awesome after my "less oil-setup". Unused travel is again at approx. ~4cm.

How come?? Does the 998S TIN-Showa's have stiffer springs then a 996?? Or is the internal damping harder?? Does anyone know the springrates of each model?? Are these numbers printed on the forksprings??

Please help I'm confused a bit: It can't be, that I still have so much travel left, but already took off 30ml oil than the recommended amount!! I really don't ride THAT slow.
The bike is turning in bad, so that it just can't carry the speed into a corner, it starts to go wide and I have to brake more than I want. I loose so much speed here that I'm 2 seconds slower than with my 20Hp weaker 996....that's soo bad!!!!

[NC Rick]

Did you make measurements to be sure the forks were the same length and installed to the same front ride height? Are you running the same sag? Tires? The 916 series of bikes came with spring rates in the same ball park (around 1.0 KG) but not every year was the same. Many people change springs and even valving so it is not easy to know if the forks are the same. I do not know if the valve stacks were the same through all the various years and models. Did you measure your oil height with the springs in? Variations in height can be significant with differing spacer configurations. We would measure the springs on a spring rater to see what you have but often, aftermarket springs will be engraved on one end with a rate...

[Connader]

The forks have the same length, it's the same fork just with TIN-tubes. I installed them the same height, took the same setup (preload, comp., reb.). The oil height was measured with springs removed, fork fully compressed. (think this is the right way to do it?!?)

The good thing is: I do still have the old fork here and so I'm able to compare. Maybe I guessed wrong and put a bit more oil in it than on the old forks, but it would'nt be much and its definitely less than stock, but still so much unused travel left?? It's really pi*** me off!!!

Thanx for the reply Rick!!!

Does anyone have some experience with oil height on this bike?? My weight is 207lbs with full riding gear.

[Ben710]

Originally Posted by Connader

The oil height was measured with springs removed, fork fully compressed. (think this is the right way to do it?!?)

Yes correct.

If you are looking for serious help, you need to provide us with proper information. sag front and rear, fork level above the triples measured on the inside (rings showing), rear ride height (do you have the ducati tool?), rear shock spring rate.

I would have left the oil alone and fill it to the recommended level from the workshop manual. 30ml sounds a lot just to have a change!

I usually work with fork preload and less compression damping if I have a lot of unused travel. Hence I am quite surprised you´re ripping the fork apart to change the oil level before you had a go at the funny adjuster knobs.

Have you been at Oschersleben? Laptimes below 1:50 this time?


:edit:
999 workshop manual states:


recommended oil:

SHELL ADVANCE FORK 7,5 or
DONAX TA

capacity per fork leg:
0,480 dm3

Standard-oil level:
104 mm (I think that´s air gap as per your measuring procedure).

[Connader]

Hi Ben,

sag at the front is 37 (loaded), if I remember, 30 at the rear. Fork position std. 3 rings showing inside, back near std. (no, no tool here) 75'er spring at the back in a Wilbers shock.

Surely I dealed with the knobs before, but I made all my experience with them 3 years ago in Poznan. The preload adjusters all almost turned out (7 Rings showing) and comp. 4 clicks from fully out.

Changing compression damping is no solution for this issue. I tried that before and had too much push at the front, mid-corner!! The Oil-level defines the progression of the springs, actually when the progression starts to rise. Changing oil level means nothing but when the fork becomes harder. So this should be the right way to go (maybe beside switching to softer springs!?!). You know: I figured that out already and it started to work just fine on my old fork, so I'm just wondering why not on this new one anymore?

I honestly thought about letting the fork reworked by Rooske, as I read your thread in your blog, but after my oil-level change at my old fork I had no problem with that anymore, but now I consider doing that again!


You see: If I remember right, the 996 manual stated 492ml per leg, the old 916 did had 470, (your 999 now says 480).....Ducati played with that. And I did 30ml less than those 492ml my 996 manual stated....so it's not THAT much difference to the 916 rec. 470ml. It worked fine!!!
Just had a look at the bottle: yes 7,5'er oil from wilbers!!

Yes I've been in OSL on friday and it's been really weird: my new 998S engine is just awesome, so much faster, the Brembo-radial-pump makes such a big difference in braking, man, I outbraked so much of those guys....I really felt so much faster but was 2 seconds slower than before with my 996!!!
The only problem I really had was entering a corner. The bike has this "nose high" attitude that it was really hard work to come around a corner. I feel like I should drop the front to get the geometry work again, but this is stupid regarding the fact that there is 4 cm (!!) unused travel left. The fork should drop itself through work!!

I'm going to strip both forks down today and compare the levels. Maybe I messed up the numbers. If not, then there really are different springs in there and I'll swap them.

Thanks for now, I think I'll test it again at the "Biketoberfest"...will you also be there??

:edit:
Just opened up the old fork: the airgap is exact 135mm, wich is recommended per my 916 manual, and is the amount of 480ml (sorry I said 470 before...wrong!!). My 996 manual says 132mm airgap, wich is supposed to be 492ml. Interesting that the 998 service-book states the oil amount of that fork again at 480ml!!! (no airgap-data here!!)

@Ben: are you sure that airgap is right at 104mm?? Maybe the 999-Showa is changed somehow?!?

Now I go into the garage and check the 998's airgap!!

[Connader]

Ok...finally I found it: opened the 998S fork and measured the Airgap: the right side was ok at ~131mm, BUT the left side had (!!) 80mm of Airgap!!!!
could'nt believe it, but I realized as soon as I removed the cap that something was wrong, as I could see the oil-level, what was impossible at the other leg (oil-level was much deeper).

I don't know how this could happen, as I still have the forkoil-bottle here, wich had 1litre, now about 40-50ml left, what "spot on" is at 480ml per leg!!

The only explanation is, that I forgot to pump out this cartridge, as I took out the old oil back then. I have no other idea!!

Put in new oil, this time with checking airgap at the end, and I do now have nice, exact 135mm airgap in each leg. This worked just fine on my old fork and I hope it will do here also!!

Sorry guys for bugging you with my stupidity and thx for the help!!!

Greetz,


Dali!!

[NC Rick]

I like to measure the "air gap" with the springs in. It is harder to do but for me, accounts for more variables. Many of the 916 type forks have a thin tubular spacer below the spring. If another fork did not or the spring wire diameter was not the same (anything covered in oil that displaces some of that oil) you would get a significant change that would not be accounted for. If your using the factory spec, then for sure you need to use the factory method (on the correct fork). Keep in mind that a 10CC change in oil volume (a small volume , well under tablespoons worth) can make a 5-10mm height change and that would be significant (particularly when running height above 120mm).

[Connader]

Hi Rick,

ok, I just want to go by the factory's recommendations, so I had to use their way to measure. Your point sounds logic too. I also wondered if I had to remove that spacer too, to measure or with in the tube?? Manual is not very clear with that!!

I'm fine with that 12ml change, because it's now absolutely via the 998 manual!!! The 996 went just (whyever) to 492ml, I put in the 916's recs., wich are also the 998 ones!!
In this case 12ml was equal to 3mm airgap. Not a too big step!?!

I just read a nice article about setting up forks with the right spring and oillevel. Pro's fix that first, before they turn the knobs!! To me, regarding that issue I had on friday (well, the reason was my stupid fault, ok), the oillevel was the only variable to fix that problem and obviously it is.

Here's the article on a very interesting side: Peter Verdone Designs - Suspension

Go to "oil-height".

Thanks for the help,

Greetz,

Dali!!