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Discussion Starter #1
Hei guys,

I know this has probably discussed already but I am about to ugrade my rear linckage with a flat one on my 1198s.

I will explain what I have already modify on my rear: I have bought a FG Gubellini FQM31 can be seen on the Gubellini's own site) and they use to set the spring harder than it should be with the OEM link. As a matter of the fact the spring is 95Nmm. I talked to a Gubellini's engineer and they told me that the spring is harder than a Ohlins' one, so this means that the spring is probably a 100Nmm Ohlins. So you can easly understand that the back of my bike is "stone" hard and I do not hit the parameters recommended for the SAG (rider i mean!). Waht i did than is to higher the bike through the rod and unload the spring almost as much as I could... of course the bike it is not behaving as I want!

So that I am considering now to update the OEM link with a flat one. The possibilities on the market are multiple and all of them suppose one to shorten both the rod and the shock and at the same time go up 2/3 steps with the spring stiffness (about 10/15Nmm).

Now, after this way of thinking since my shock has already the right stiffness I should just vary the total lenght of the shock itself and the rod one.

I was also told by the engineer at Gubellinis that with a linear link the shock do not need to be shorten or to be chanced the spring! They design it to work linearly and not progressivey!

So I think I am going to try a flat link (I do not know which one yet) and try to get the parameters in the ball park as it is. If I cannot reach a good level of feeling than I will probably start touching both spring stiffness and shock's lenght.
I know that this shock is at the moment one just piece of art but it is quite hard to understand how it works! :-(

My question is now: is there anybody who has experience with this kind of shock? Waht do you suggest then.

I really appreciate any kind of help from you!
 

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:eek:ok, ive been doing a 1198 swingarm on a 996 mod, i have found that in order to change the rear suspention from prog, to lin, you need to do more than just "flattern" out the pivot connector or be careful how you do it.

its all about ratio!!

if you see the holes in the pivot as a,b,c

"a" holds the shock,"b"is the fulcrum,"c"is the ride height

in order to maintain "progressive" movement you needto maintain distance
"a" to "b" and "b" to "c"

so you get no change on the stock item.

if you want "linear" then you need to maitain distance bettween
"a" to "c" and move "b" (that is now off set) to give a ratio of about 2:1

so my point!! lol :D it depends how you fattern out the lynk, as to how it affects the bike as in my first example, this will just affect the ride height, or the second example, this will affect rideheight and ratio.

be carefull do the maths and double check the maths :D
 

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Discussion Starter #3
:eek:ok, ive been doing a 1198 swingarm on a 996 mod, i have found that in order to change the rear suspention from prog, to lin, you need to do more than just "flattern" out the pivot connector or be careful how you do it.

its all about ratio!!

if you see the holes in the pivot as a,b,c

"a" holds the shock,"b"is the fulcrum,"c"is the ride height

in order to maintain "progressive" movement you needto maintain distance
"a" to "b" and "b" to "c"

so you get no change on the stock item.

if you want "linear" then you need to maitain distance bettween
"a" to "c" and move "b" (that is now off set) to give a ratio of about 2:1

so my point!! lol :D it depends how you fattern out the lynk, as to how it affects the bike as in my first example, this will just affect the ride height, or the second example, this will affect rideheight and ratio.

be carefull do the maths and double check the maths :D
Hi,

and many thanks for the answer! But I am not quite sure I understood which distances you are talking about! Maybe a sketch will make it easier! :D
Do you have time to make one really quick!?

I will be reaaaaaaally thankfull for this!

BTW Are you trying to tell me that it doesn't matter which shack you have on the most important thing is to respect the ratios you talked about?!

Which flat link do you suggest to use!? I was thinking about the Metaltech one!

Stefano
 

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yea, sorry i was quite drunk when i posted last night but it is basicly right!

i was on about the pivot rocker from the suspention set up, and i assume you were too. it has 3 holes one for the bolt that secures the shock,one that bolts the rocker to the frame and one for the ridehieght ajuster,

i will put a drawing together for you lol

if you flattern the rocker out you will affect the ride height but nothing else the rs/course rocker has a different ratio of movement of about 2:1 this means the shock compresses by 10mm and the ride height moves by 20mm ratio 2:1

dont bye a shorter shock this will affect how the bike sits and the range of movment!!

i also assume you are alfter a "racing" set up for the track,
 

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Discussion Starter #5
Thanks mate! Yeah i have 1198s track bike and I'm about to mount a triple as well with 28mm offset! Podium Racing will assist me!

Wait for your sketch! ;-)
 

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Discussion Starter #6
Quick question: rs/course you are talking about are 2 different flat links? Or it is just the Corse one?! And is this one havin a ratio 2:1?? Or maybe all flat links have the same ratio!??!

Sorry but I am getting a little confsed now!
 

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Hi sorry i took so long (i had to walk the dogs)

here are some pics for you so you and others can see what we are on about!

pics 4/5 are hand drawn im sorry about that lol.

anyhow pic marked as (1) shows what happens when you just flattern the pivot rocker out this will have the same affect as just adding a longer ride height bar!

pic marked (2) shows moving the falcrum, this affects the ratio of shock movement to swingarm movement. the rs/course item provides liniar suspention at a ratio of about 2:1 or 10mm shock movement to 20mm of swingarm movement

some of the guys on hear know alot more about this than i do, the only reason im in the know is due to doing a swingarm swap on my 996 i hope this helps
 

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Discussion Starter #8
I am not sure I am understanding what you are tryng to tell me! Is it any connection between pict 1 and 2 or they are just two disconnected effects! One when you flatter the rocker and the other one??? I do not understand! Sorry for this!!! can you just compare the geometry of the OEM link 81098/1198) with the Corse Link. So that I can see what is changing between the 2!
 

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I am not sure I am understanding what you are tryng to tell me! Is it any connection between pict 1 and 2 or they are just two disconnected effects! One when you flatter the rocker and the other one??? I do not understand! Sorry for this!!! can you just compare the geometry of the OEM link 81098/1198) with the Corse Link. So that I can see what is changing between the 2!
ok in pic (2)

the position of point (b) is changing the distance bettween point (a) and (c) remains the same

this would be the course factory lynk, by moveing the fulcrum (point b) you change the affect that point (a) and point (c) have on each other

the best way i can explain it is:

two kids sit on a plank of wood balanced on a box (fucrum) the box is in the middle and when the kids rock the plank they go up and down at the same rate up 1mtr at one end and down 1mtr at the other, a ratio of 1 to 1
When they move the box they change the ratio so one kid might still go up and down 1mtr but at the other end there mate is now going up and down 2mtrs to there 1mtr or at a ratio of 2 to 1

the same is true for the pivot lynk on your bike

just bye a ducati course flat lynk it will have the correct ratio lol job done no need to replace the shock or modify it and just use your ride height lynk problem solved unless you feel the need to see how it all works
there are some threads that go into it and give you all the graphs and figures:eek:
 

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Discussion Starter #10
Yeah! That's what I was thinking! I will make a model tomorrow and try to apply unitary displacements and see what happens both to the rod and the shock. In the meantime if you could send me graphs and picts it would be a plus! Do you also have all the distances between the points in question? I mean the following:
- distance between frame/swing arm pivot and back wheel axel
- I have the lenght of the shock and the rod height
- geometry of the OEM rocker
- geometry of the Corse rocker

Thanks! ;-)
 

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Discussion Starter #11
ok in pic (2)

the position of point (b) is changing the distance bettween point (a) and (c) remains the same

this would be the course factory lynk, by moveing the fulcrum (point b) you change the affect that point (a) and point (c) have on each other

the best way i can explain it is:

two kids sit on a plank of wood balanced on a box (fucrum) the box is in the middle and when the kids rock the plank they go up and down at the same rate up 1mtr at one end and down 1mtr at the other, a ratio of 1 to 1
When they move the box they change the ratio so one kid might still go up and down 1mtr but at the other end there mate is now going up and down 2mtrs to there 1mtr or at a ratio of 2 to 1

the same is true for the pivot lynk on your bike

just bye a ducati course flat lynk it will have the correct ratio lol job done no need to replace the shock or modify it and just use your ride height lynk problem solved unless you feel the need to see how it all works
there are some threads that go into it and give you all the graphs and figures:eek:
BTW what about the spring rate? Would you just hold the one with the OEM rocker?

P.S. Send me the graphs and figures you have! It will help me understanding! ... and some mesures if you have them!
 

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have a look at this thread

848 Swingarm on a 1997 748....what's needed for the swap?

theres some interesting info on here!

i dont have the figures to hand or the dimentions of the course rocker butthis thread is a good one
 

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Discussion Starter #13
Ok. I will check it out!

Have you installed the OEM 848 rocker on your 996? Do you have the distances between the bolts?!
 

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The need of a shorter shock with the flatter is because of the clearance with the shock reservoir.
With the normal link the inclination makes that the link clears the reservoir, the flatter sits closer to the reservoir. The shorter shock makes the rocker have an back inclination that clears the reservoir.
 

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Discussion Starter #15
The need of a shorter shock with the flatter is because of the clearance with the shock reservoir.
With the normal link the inclination makes that the link clears the reservoir, the flatter sits closer to the reservoir. The shorter shock makes the rocker have an back inclination that clears the reservoir.
Well maybe your right! This can be one of the reasons but I honestly think that there are some ratios between distances that MUST be respected else one could have had a really short shock and really long rod and make everything linked anyway!

We must understand that if we do not set the connection points of the rod/shock/link within the specs they need to be at, we probably inherently change rate of the link, either progressive or regressive.

The other issue one will face is the relation of the shock/rod position versus the geometry/angle of the swingarm. By using a shock too long with a rod too short, one flattens the swingarm, causing too much squat effect, not to mention the many other issues one creates. Let's go opposite of the first issue and by using a shock too short and a rod too long; result may create a regressive rate initially, though serious binding mid-compression, resulting in one doing his best superman routine: SUPER HIGHSIDE!!!!!!

Well, not because I know what I am talking about... but I guess there is much more than a simple clearance issue here! Else in MotoGP, SBK an so on will use the same link on every track! But it is not like this!

The problem is to know which ratios one has to respect to be in the ballpark! :eek:
 

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Discussion Starter #16
The need of a shorter shock with the flatter is because of the clearance with the shock reservoir.
With the normal link the inclination makes that the link clears the reservoir, the flatter sits closer to the reservoir. The shorter shock makes the rocker have an back inclination that clears the reservoir.
And BTW I do not have clearence issue with my FG Gubellini!
 

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And BTW I do not have clearence issue with my FG Gubellini!
The clearance issue is just with the original shock and the linear link.

In general the standart shock has to be shorten by 7mm to work with the linear link.
 

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Discussion Starter #18
The clearance issue is just with the original shock and the linear link.

In general the standart shock has to be shorten by 7mm to work with the linear link.
Well I am posting also on other threads and the lenght of the shock is not an issue when it comes to clearence. But everyone is entitle to think whatever he wants! ;-)
 

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Well I am posting also on other threads and the lenght of the shock is not an issue when it comes to clearence. But everyone is entitle to think whatever he wants! ;-)
I'm also thinking of buying a linear link to my 1098, and the problem was brought by Dan Kyle and Mark from DucShop, as i wanted to use the original shock os the 1098S.

As you can see Ducshop sells a part to shorten the original TTX from the Ducati.

Ducshop TTX Eye end from Ducshop Products

But you with you FG don't have this problem, i have a Bitubo and is also adjustable in lenght, one of the reasons for the buy. :)
 

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Discussion Starter #20 (Edited)
I'm also thinking of buying a linear link to my 1098, and the problem was brought by Dan Kyle and Mark from DucShop, as i wanted to use the original shock os the 1098S.

As you can see Ducshop sells a part to shorten the original TTX from the Ducati.

Ducshop TTX Eye end from Ducshop Products

But you with you FG don't have this problem, i have a Bitubo and is also adjustable in lenght, one of the reasons for the buy. :)
Well, as long as I know the eyelet is sopposed to be mounted on a TTX and not a DU... (I do not remember the model precisely) ... Anyway I guess one shold fit the OEM Ohlins with NO intervention on it! ;)
 
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