rear shock

[yambutt]

If I raised the rear end with adjustable dog bones to about a inch or so higher do I need a longer shock, if I recall I think I shortened the dog bones, they are the soupy adjustable dog bones, to raise the rear, so how would I measure to see how much longer I need the shock to be, thanks yall.

[Derek Young]

No need to get a longer shock. You might enjoy a new one though, if you are running a stock shock.

[yambutt]

Klaus with hyperpro says I do, he's a builder for them here in the usa

[jscgdunn]

He is wrong or confused by your request.

[yambutt]

I thought so to, I told him that I have adjustable dog bones and raised it about an inch, he said measure the space between it and the ground while bike is on centerstand, then put old dog bones on and remeasure, and that would be the difference.

[yambutt]

Measuring the gap from rear tire to ground

[yambutt]

My guess is if I kept the soupy dog bone where there at now and got a shock one inch taller wouldn't that raise the rear even further, I think he is getting confused of me wanting to put my original dog bones on with the taller shock so I would still have the height I have now, maybe thats what he's getting confused about

[Pat Conlon]

Klaus with hyperpro says I do, he's a builder for them here in the usa

Do you *need* a longer shock? No.

Will a longer shock raise the back end? Yes.

Between the options of 1) shorter dogbones vs 2) longer shock, which option is better?  Longer shock.

I think what Klaus is saying (and he is correct) is that the longer shock option is preferable over shorter dog bones because the longer shock keeps the swingarm linkage geometry stock as the engineers at Yamaha designed it.
When you shorten the dog bones the angles on the linkage (relay arm) change and the articulation of linkage is different which affects the compression/rebound characteristics of the shock and spring.

That said, many of us use shorter dogbones with no ill effects.

I use both options, longer shock (Penske) and adjustable dogbones.

I too have Soupy's adjustable links and I have a point of caution to warn you:
When you adjust the links, be *absolutely sure* that each side is equal in length. I mean equal down to a nat's ass. If each side is even a milimeter different this will put an uneven load on the bearings in your swing arm linkage and you will ruin them is short order. Ask me how I know.
I set the rear height where I want it using only 1 adjustable link....then take that link off the bike and up to my work bench where I set the 2nd link equal to the first link. You must be precise.

[Firehawk068]

I'm sure Klaus means well, but he is probably not familiar with the rear suspension on the FJ.

If yours has dog-bones, there is essentially TWO swing-arms on your FJ.  One is the transfer arm, that connects the bottom of the rear shock to the frame. It's relationship to the frame, and the rear shock never changes. It simply moves up and down with the compression and rebound of the shock.
Then there is the swing-arm that the wheel is attached to. It is connected to the transfer arm with the dog-bones. By shortening or lengthening these dog-bones, you are changing the relationship between the swing-arm, and the transfer arm. This will raise or lower the rear wheel in relationship to the frame. The length of the shock has nothing to do with it.

It is possible to get the same result by altering the length of the shock, but most people alter the length of the dog-bones instead.

Not all FJs have dog-bones on the rear suspension. If I'm thinking correctly, it is the '89-up models. (Possibly '88 Jap and Euro models?)
The only way to raise the rear on the early ones is to lengthen the shock.

oops, Pat beat me to it.  


Early FJ



Later FJ

[yambutt]

Thank yall all so much, I think I will go with the taller shock and put the original dog bones on, that to me seems the safest way....

[yambutt]

Oh so if I go with taller shock and original dog bones should I then adjust chain back to 3/4 of a inch instead of the 1 1/4 I have now

[racerrad8]

Pat, sorry, I have to disagree and so does the company that manufactures the RPM shock for me.

The longer shock changes the relay arm linkage geometry to the shock affecting compression & rebound functions. That is why I do not offer an adjustable length shock as it changes the required valving within the shock.

Yes, the dog bone length does raise or lower the bike by changing the distance of the swing arm in relation to the relay arm which is the proper way to affect ride height changes, but it does not affect the shock valving or performance.

Just loo at the really long BMW shock that Fred installed prior to the RPM shock he has now, that is a drastic change to the relay are geometry and requires different valving to compensate.





Stock shock length is always better because the Yamaha geometry stays as designed.

Longer shocks only move the relay linkage down and out of the original geometry design...

Randy - RPM

[Pat Conlon]

Randy, yes there are extremes where a longer shocks can be detrimental.

I'm relaying advice I've been told by several motorcycle suspension experts.
Jim Lindemann (RIP) Ed Sorbo at Lindemann Engineering, and Donnie Jenkins at Traxxion Dynamics just to name a few.
In addition several shock manufacturers (Penske, Hagon, Ohlin, Fox) will also disagree with you.

So we know about the handling benefits of raising the back end of our bikes (I don't think there is disagreement there, correct?)
Randy, does this mean that your shock will *never* have the length adjustable feature so the folks who have the '84-87 FJ's (no dogbones) get the ability to raise the back end (like folks who enjoy the option on the '89-93 FJ's)

The Penske shocks have a 3/4" range of adjustment on the shaft of the shock....is that a really big deal?  Really?

With respect: I think the opinion of your shock manufacturer is self serving.  

[racerrad8]

Self-serving...yep bet your ass.

Sorry, I don't know Ed Sorbo or Donnie Jenkins and frankly their advice to you is probably pretty general based on their experience with all kinds of bikes, not the FJ specifically.

Are you really being serious to tell me they have spent any time with 30 year old FJ specific motorcycle testing?
Did they invest in an FJ and design a shock specifically for the FJ?
Did they ask Penske, Hagon, Ohlin or Fox to design a FJ specific shock?
Do any of the above manufactures offer any patented technology?

Pat, you are right, those guys who work on all kinds of shocks on all kinds on different motorcycles are specialists in their area and according to their advice to change the shock linkage you have found that be be the gospel.

But they are still working with a universal product that is adapted to fit your FJ as well as a bunch of other applications.

Since we are calling out shock people, after working tirelessly with Don Richardson and Brian Salter of Ricor on the development of the Yamaha FJ specific RPM rear shock, I feel they are spot on with their advice of not altering the shock linkage geometry. Hell, Don is the one who designed and patented the IAT system that no one, I mean no one can use without paying the rights for it.

Does Penske use it?
How about Hagon, Ohlin, Fox or any other shock manufacture...nope.

Does any other shock actually offer a truly tuned shim stack rear shock for the FJ...Nope.

They can't build the true, proper shim stack for the FJ; they have to rely on a weak shim stack and "adjustable" orifices to tune in your shock for your specific motorcycle. Why, because no one would buy a true shim stack shock because it would right like shit on the road; much too stiff. That is why you have to have your remote reservoir and adjustments on the shaft, to compensate.

No matter how you slice it, every other shock on the market is a universal product for a wide range of motorcycles and it also happens to fit your FJ.

During the design of the RPM shock, did we try altering the shock linkage geometry; yes, did it work...nope.

Will there ever be an adjustable RPM FJ specific shock...nope.

And finally Pat, is 3/4" a big deal, yes it is. Depending on which linkage system you are looking at it is a pretty severe change of the relay arm and that does several affect the valving of the shock. The distance from the relay arm mounting/pivot point and the shock mounting pivot, compounds the leverage required the farther it gets away from the factory designed center line. Does your shock offer a way to compensate for that, yes it does with all of the "adjustments" you can make.

I will hold fast on my learning experiences of designing and applying the best and patented shock technology to the FJ. Maybe when Ed Sorbo or Donnie Jenkins patents some new technology, spend the time & money designing it specifically for the FJ then I might take their advice. But for now, I will stick with the ones who worked with me, investing their time and money with me for a FJ specific shock application, not a universal product that just fits and you can adjust.

Am I suspension expert?
Maybe not an expert, but I do have a lot of shock tuning experience from my race car days I fully understand how it all works and I am definitely not a garage hobbyist relying on the advice of others. My experience assisted in the design of the RPM shock with Don & Brian as I was actually able to give them proper feedback in designing and ultimately producing the only aftermarket shock for the Yamaha FJ1100 or FJ1200.

Sorry, no universal application shock available from RPM; you have to call Penske, Hagon, Ohlin or fox for that.

Self-serving...you better bet your ass.

Randy - RPM

Now, I am going to go to lunch and then start back to work on your FJ when I get back.

[yambutt]

So randy do you have a used rpm shock in great condition in the $500/600 range?