Speed Triple Single Sided Swingarm Installation

Thanks for the in depth input Josh. I think that I'll let the top shock mount be- That seems to be the consensus amoung the monoshock veterans

As for the frame flex around the swingarm pivot, There isn't a whole lot I can do. The upper rear motor mount will be there to help keep things from trying to pull back together, but the truth is that there really isn't enough room below the motor mount for another brace without getting into the chain run. I'd like to think that if the same forces existed on the stock swingarm, and the stock bracing/mounts were enough to mitigate any harmful flexing of the rear down tubes, then the mods I've made should help to reduce even further any tendancies to twist or collapse. Unfortunately what I'd like to think doesn't always match what really happens. Clearances are close enough that if what you say is true, then I'll start chewing up the top, outer edge of my swingarm. I wonder though, if the forces existed on the stock swingarm, and there were no problems with it pulling the rear down tubes together, am I adding any additional force to exacerbate the problem, and would having the frame wider necessarily cause any pre existing problems to magnify?

I'm thinking that u are stronger than stock, now. u may be wider , but u now have cross braces. any current tube is now braced,so it should act as it is shorter then the original ,as far as loads go.
i think the most important load that need to be considered are any torsional loads.
The new arm has some big pluses over the old 1. it has built in side thrust bearings, and a stronger pivot bolt. both of which are week points on a stocker. These alone , will add to the torsional resistance.
I think the next week point will be above, as the rails meet (in front of the seat)and go forward.(between your braces and the neck.)

I went back and studied your top, rear motor mount, and I think that it will be enough. I was just pointing out what may happen under extreme conditions.

I don't think that you have necessarily increased the total load on the rear part of the frame. Unless you are useing a higher rate spring, and increasing the total weight of the bike at the same time. However, you are significantly changing where the load is applied. With the original twin shocks, the forces are concentrated at the rear of the swingarm, and the rear part of the subframe. Also, since the shock is nearly verticle, the loads are straight up and down and directly opposed. The new setup concentrates all of this load to the same area of the frame, and it now means that the swingarm is acting on the lower part of the shock through a much longer lever now.

With all that said, I think that you're fine with what you have.

The question now becomes: Is my configuration necessarily that much different than any other monoshock conversion? It cannot be disputed that I'm transfering the rear suspension forces to an area of the frame that was not originally designed for it. But is the lever for the bottom shock mount much different than yours Josh? Or OMR's or Larry C's for that matter? I know that your upper shock mount is lower in the frame and closer to the down tubes than mine is, but aren't the forces being transferred in the same manor? I suppose the most basic question I have for you is whether you have the exact same concern with your conversion mods, and if not, why? I'm not trying to badger you, and I'm certainly not getting defensive, just curious.
:laugh:

the lower right welded area where it is blue and slag colors...is gonna wanna flex away,even thought you have pushed the top mounts forces back at the shock with the nice upper V....that really imo only resets the fight between that lower right weld and the frames side cover cradles....i think that that weld will still have flex...it will still be at odds with the side rails and the shock and V arm wrestling....i think a small "1 -1/2 " long point to long point support running from the side rails below your cross member up to its underside at the crossmebers 90* turn ins ,would support the struggle of the shock and upper V....make any sense...looks good...it would hold now most likely but i see it offending that blue area much like a shelf with heavy books lossens the shelfs support pins over time...there is not just the force of the swingarm movement and chain drive lash acting on your support...there is also the wheight and torque of you on the seat loading all the frames junctions,...do you also have room to add another rectangular crossmember in front of the swingarms pivot points a tying the sides togehter in unison with the rear upper motor mounts...under the engines rear upper cross mount rod and in front of the battery bay....to keep the single sided arm from try to buckle the side rails???
porchev914 wrote:

In the pic above it looks like the top braces are rather vertical, but the truth is they are layed down a fair amount-

I think that I may still add some small corner gussets under the cross mount at the frame....any opinions out there?

porchev914 wrote:

The question now becomes: Is my configuration necessarily that much different than any other monoshock conversion? It cannot be disputed that I'm transfering the rear suspension forces to an area of the frame that was not originally designed for it. But is the lever for the bottom shock mount much different than yours Josh? Or OMR's or Larry C's for that matter? I know that your upper shock mount is lower in the frame and closer to the down tubes than mine is, but aren't the forces being transferred in the same manor? I suppose the most basic question I have for you is whether you have the exact same concern with your conversion mods, and if not, why? I'm not trying to badger you, and I'm certainly not getting defensive, just curious.
:laugh:

No, in my mind it's not any different at all as far as the relationship of the shock, swingarm and frame are concerned. The only major difference in mine is that I still have all of the rear subframe in place, and I did add gussets to the subframe connection to the main cradle. My crossmember is a 1/4" piece of plate with a piece of 1/8" across the top. I hope that it all works on my bike. Actually, I have a certain amount of concern that the original swinarm pivot bolt is the weak link in my system now. The GSXR bolt is a hollow piece that is quite a bit larger in diameter. At this point I'm going with what I have. Part of the reason that I plan on painting my frame instead of powdercoating. I expect changes in the future based on actual riding experience. Its not possible that I'll get everything perfect the first time.

Damn it. Josh and Tri are actually right, I believe. The force of the shock is more vertical than the "V" bracing above the shock mount. The weak point of the design is the tops of the "V" brace is now the pivot point of the lever, and it will be trying to pull the cross tube at the weld on the down tubes. While I still don't believe there is enough movement available for the down tubes to be pulled together, I could certainly see tension cracks forming on/around the welds at the bottom of the cross tube shoch mount.

trust me when I tell you this...it AINT going anywhere! period
the 73 has no bracing....and a whole bunch of HARD launches plus some street time with an extended swingarm....no cracks no issues what so ever....for it to pull at those welds...the top V bracing would have to bend....not gonna happen
it says kawasaki on the tank....not MACK!!

just my .02

Thanks for the reassurance Ben. I was hoping to keep it simple, elegant and strong without throwing steel in every direction.....I'm gonna sit on it a little and let it digest while I work on reinforcing a few other areas of the frame.

Just ride it and keep an eye on it. You know damn well that you will be inspecting those welds after every ride for a while. The first time you hear a pop or a ting you'll pull over and inspect. I bet it works fine.

porchev914 wrote:

Thanks for the reassurance Ben. I was hoping to keep it simple, elegant and strong without throwing steel in every direction.....I'm gonna sit on it a little and let it digest while I work on reinforcing a few other areas of the frame.

you have a good head on your shoulders....everything you've done so far is awesome!
its hard to wade through all the opinions...including mine....follow your instincts....by the looks of things they havnt let you down very often

again just me rambling....no offence to anybody

porchev,i am actually marks translator :laugh: .i know,i know yes i speak canadian .when he asked about tieing the three tubes together in front of the seat he meant like this.


just trying to help my buddy clarify.:ohmy:

leon