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Discussion Starter · #1 ·
Two questions:

1) Linear rate linkage is better than progressive, right? It won't rise in stiffness and pogo like progressive does.

2) I have custom dogbones that are a few mm shorter than stock. It raised the bike by about 0.75". Anyway, did this make it more progressive, or more linear?
 

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Aren't they all progressive? I thought that was the point.
 
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Discussion Starter · #3 ·
If it's too progressive, the rate will rise too much, meaning that it will rebound too strongly and act like a pogo stick. I have read articles about race teams who changed their linkage to make it less progressive (more linear). Thus my question.
 

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If your bike is pogo-ing I doubt it's the linkage but I'll let the techies handle it. Maybe I'll learn something too. I would think it's a damping issue.

The way I sees it, with a (hypothetical, don't think they make many) linear rear end the shock would compress more so store more energy and be more prone to pogo. The progressive linkage allows the shock to compress less for a given wheel movement.
 
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Discussion Starter · #5 ·
Dillweed said:
Two questions:

1) Linear rate linkage is better than progressive, right? It won't rise in stiffness and pogo like progressive does.

2) I have custom dogbones that are a few mm shorter than stock. It raised the bike by about 0.75". Anyway, did this make it more progressive, or more linear?
dog bones dont change how suspension works.linkage does not move with change of dog bone,swingarm does.
position of swingarm in its travel can affect suspension due to anti squat forces.
reason everybody is saying dont mess with linkages is because you must know exactly what you doing and it is not simple.it is all relative to center of gravity.
reason linkages are on bikes is use of single shock that is closer to frame for packaging and travel.they also give option of changing progressivness or even digressive.
 

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That is wrong. First this part of his claim is basically okay "linkage does not move with change of dogbone,swingarm does, position of swingarm in it's travel can effect suspension due to anti squat forces"

As long as the shock length is the same, the linkage position relative to the linkage frame mount and swingarm pivot is the same. The relationship to the swingarm dogbone pivot has changed and the effective radius of the dogbone pivot has changed as well as the swingarm down angle. All of that has a effective change associated with it. The numbers are small but there is change.

This part is garbage "dogbones don't change how suspension works" "it is all relative to the center of gravity" If the swingarm didn't move and with it the dogbone mounting point, and the dogbone pivot arc stayed exactly the same this could possibly be true. Read this a couple of times and give this some thought.

The dogbone mount moves with the swingarm and is only constant with the swingarm pivot and axle locations. The linkage is only constant with it's frame mount point and it's arc of travel. The two pivots are not parallel or constant to each other but both serve to transfer force to the lower shock mount. Those two pivots with the difference between the them and the swingarm pivot create the linkage relationship. Thus the rate of progression changes due to the change in the arc of the dogbones in relation to swingarm movement and in relationship to the point on the bell crank the linkage is at within it's travel arc. Shortening the dogbones does not move the swingarm to a point earlier in the linkage progressive curve. The linkage starts in the same physical position, but because of the effect of the shorter dogbones and swingarm position the linkage effect is initially less progressive due to the shorter radius or arc of the dogbones and reduced mechanical advantage so the force the shock exerts on the swingarm is changed. The swingarm moves the linkage slightly less for a given amount of movement at the axle and the result is a less progressive linkage overall ratio. Keep in mind these numbers and rates of change are small, but they are real and have an effect.

None of the mechanics of the suspension movement have anything to do with the center of gravity. The dynamics of it's operation is greatly effected by the CG, so CG has an important place in setup, traction, stability, handling, etc.

You can believe Zoran if you chose to, but he is simply wrong and the truth must be told even if truth is relatively complicated. If Zoran was right, then changing the distance between the frame pivot of the linkage and the lower shock mount would have no effect on the suspension either, it is the same effect. For some reason it may be easier to grasp this that way.
 
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Discussion Starter · #7 ·
Hmm...well I may have opened a can of worms here, but I'm really just asking out of curiosity sake......All other things equal, will shortening the dogbone make the rate rise faster or slower?   

Only reason I ask is that I seem to have more "pogo-ing" after I shortened the dogbones.   I think I might have asked you about this earlier but I forgot what you said.  I was the guy with the ZX10 shock.
 

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Pogoing is the result of incorrect (in this case too little) damping.

As to the geometry, everyone break out their compasses and make a drawing of the linkage with stock components. You will see that the lever ratio of the load (the weight of bike, rider and impact loads) from the swingarm against the spring/shock changes as the suspension compresses. The advantage of the spring increases as the suspension compresses. Note that since the ratio changes you can plot a "ratio curve" with ratio vs. compression.

Now put different dogbones in the picture and you will see that what happens is that the lever ratio changes. The "start" position lever ratio is different, given equal sag settings. You alter the curve when you lengthen or shorten the dogbones.

I would not begin to predict what effect any of this would have on handling. I would bet big money that some folks would like it better one way, others another way. I would also bet that some folks would be faster on a race course with one setup, others with another setup.
 
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Discussion Starter · #9 ·
andyauger said:
Now put different dogbones in the picture and you will see that what happens is that the lever ratio changes. The "start" position lever ratio is different, given equal sag settings. You alter the curve when you lengthen or shorten the dogbones.
take look at sv(99-02) linkage.circles they make are small(compared to gsxr or even newer sv).dog bone at linkage moves about 1 inch with full wheel travel(4.5 inch or so).there is almost no difference where in circle it is to affect leverage.
that zx10 shock if stock is I believe about same lenght as sv one(some post shows 1mm difference)meaning linkage will stay in same place.dog bone is shorter and teoreticly will come to mechanical lock sooner.it wont happen unless zx shock has more travel.if it does it will allow swingarm to go further up and flaten dog bone at which point there is no movement.combine all of that with stock zx spring been to soft for sv and you do have can full of warms.
somebody needs to call suzuki and tell them to put shorter gsxr shock with shorter bones and bike will be excellent.
wait,they already did something like that on new generation sv,but they changed linkage along with dog bones.
 

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Adding in additional variables doesn't make the fact that changing the dogbone length changes the linkage effective ratio. Just because the change is small doesn't mean it doesn't change. Andy is correct.

No one is said there is a magic setting. After considerable testing we came up with two different lengths - one better for many track riders and one better for many aggressive street riders.

No said call Suzuki and tell them they used the wrong settings, they didn't develop thie linkage ratio for racing so what would be the point? You simply can't admit publically that you are wrong about this.
 
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Discussion Starter · #11 ·
what happened,you got new shipment of penis inlargment pills?you made post without insult.
lenght of dog bone will not change the way shock travels.it will change where wheel starts and ends travel(unless you go to extreme).
sv linkage is progressive in begining and linear later.with shorter dog bone this linkage will still start moving at same place it did with longer ones.only thing it will change is end of it if gone to far.it can make it regressive.
since most of this shocks(gsxr,zx) are shorter than stock it will move linkage starting point and put it in more linear part.however ride hight will be screwed.here comes cheap fix,dog bone.it puts ride hight back but does not change how progressive linkage is.shock did that.
theoreticly dog bones will change how progressive/regressive link is but with sv wheel travel of 4.9(by manual) inch or so it will not get in that part.if you have shock that has more travel it can become regressive.
 

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TWF, you're missing the point. You are correct in saying that dogbone length does not alter the travel of the shock. What it does change is the lever ratio of the swingarm to the shock/pivot. Making the dogbones longer makes the "starting" ratio lower (more load required for "x" initial deflection). Shorter dogbones makes the initial ratio higher (less load required for the same "x" initial deflection). The geometry isn't that complex.

The suspension can't be separated into its component parts. You have to look at the whole system.
 
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Discussion Starter · #13 ·
isn't that what I said before?you moved start and end point.
what did you acomplish?swingarm angle and ride hight.
did you make suspension more linear?or progressive?
 

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Actually, yes. You've made it more progressive if you lengthen the dogbones. Plot the ratio curve and you will see it's a bit steeper at 20mm initial sag with longer dogbones, less steep with shorter dogbones. Since the ratio changes with displacement the shape of the curve can be altered with dogbone length.
 
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Discussion Starter · #15 ·
andyauger said:
Actually, yes. You've made it more progressive if you lengthen the dogbones. Plot the ratio curve and you will see it's a bit steeper at 20mm initial sag with longer dogbones, less steep with shorter dogbones. Since the ratio changes with displacement the shape of the curve can be altered with dogbone length.
this is where we dont agree.I say it makes no difference.
teoreticly if you look at all circles turning around there is change,just like you can say it can never be linear as long it runs in circle.in reality you change nothing with dog bones.
lenght of shock makes bigger difference than lenght of dog bone.shock is running bigger circle(travels more).
 

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Well, it's not a matter of opinion, it's math and geometry. I don't THINK the ratio curve changes, I know it does. Shock length will also change the ratio curve. ANY change that rotates the triangle link from stock position will change the ratio curve.
 

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andyauger said:
ANY change that rotates the triangle link from stock position will change the ratio curve.
Do different length dogbones move the rocker or no?
 
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Discussion Starter · #18 ·
NOsquid said:
Do different length dogbones move the rocker or no?
no.it only moves swingarm.think about it.rocker is bolted to frame on one end.other end is bolted to shock,shock is bolted to frame.it is locked in 3 points,it can not move unless you move one of those 3 points.dog bones is just lever that pulls on rocker and compressing shock.
 
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Discussion Starter · #19 ·
andyauger said:
Well, it's not a matter of opinion, it's math and geometry. I don't THINK the ratio curve changes, I know it does. Shock length will also change the ratio curve. ANY change that rotates the triangle link from stock position will change the ratio curve.
you can say same for chain moving in curve when you put 1 teeth bigger sprocket.does it change progression of suspension?yes it does.as much the lenght of dog bone does.nothing that you can feel or measure easily or will make change to your ride.
like you said,suspension is whole thing together(which is what I said in begining but you said it has nothing to do with it)from contact point of tire to center of gravity and everything in between.
claiming that dog bone lenght will alter you suspension and make it better is marketing bullshit.in reality you just trying to bring ride hight back where we think it should be.
if different lenght dog bones are such good tool for changing the way suspension work you would see adjustable ones on every race bike(at price who would not use them).I have seen none.I did see rockers changed on some models in attemp to make it better.
I am sticking to my teory that those bones make no change on our sv.
 
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