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Discussion Starter #1
Hello fellas,
So I have in my possession a 1984 Honda Shadow vt700, I bought it for a engineering project.
I'm going to fit it with a mono-shock suspension. I have a good idea how to go about it. I'm looking into a Suzuki Hayabusa shock because that bike is heavier than mine and so with my limited knowledge i figured it would be strong enough. But I need some help with the shocks angulation and position for the mounts. I have already began to make space for the shock.
So my questions are...

Where should I start?
Has anyone ever put a mono-shock on a shadow?
How did you do it?
Recommendations for which mono-shock?

Just let me know if you guys want to see pictures of the bike (if that will help with the questions)?

Thanks guys
 

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I think you start by....measuring. Seriously. I mean to do it right you need to work with some parameters. I am assuming you are changing nothing else about the bike other than trading two shocks for one.

You sit there and figure out the full travel of the suspension, how the wheelbase will change, swingarm lenght and width, chain line, etc....

A couple of problems you need to solve for off the bat:

- The stock swingarm is not going to be sufficient. It need to be more structurally sound. You need to figure out how much and what stresses a larger "lever" is going to impart on the frame.

- travel length of the monoshock and whether you need straight rate or rising rate setup.

- the spring rates need to match the weight of the bike plus rider. This isn't just "ill just use this thing because it's heavier than my thing". First off I would be shocked if a busa is heavier than your shadow. There is a whole science behind springs, time to learn it. Same with dampening.

- your rear subframe will no longer be able to hold a passenger. Need to figure out how to reinforce or redesign.


there are other things you need to consider if you are to do this right. Of course you can just be like one of these dipshit "cafe" builders and stab in whatever works and hope you haven't built a death trap. BTW, you aren't building any kind of "cafe racer" with this project, I don't know what it is but it ain't what you think it is. Nothing wrong with that as labels are garbage anyway, but you really need to figure out what you are improving with this and what your need is. So I guess the first step is answering "what is inherently better about a monoshock that I need to swap it in for my dual shocks?"
 

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Discussion Starter #3
Yes sir!
Thank you for your reply.

For now yes the only thing I am focussing on is the mono-shock suspension.
The bike came without out any suspension, it came as a hard tail with two fixed supports. Bu to answer your last question first I want a mono-shock because (however little) it will save weight. With a mono-shock the bikes suspension can be more easily adjusted, however unlikely there is a chance that the dual shock can operate unevenly.
IMG_3598.JPG

I figured about the swing arm, however this bike has a shaft drive system.
That being said do you think I should look for a new swing arm or, strategically redistribute the stress and re-enforce it?

As for the mono-shock, by straight rate do you mean horizontal positioning of the shock, and by raising do you mean diagonal to vertical positioning of the shocks?
If that is the case, from what I have seen form this bike is leaning towards a raising rate, because I would like to set the resting height a few inches higher. Thoughts?

Form the research I have done "my" shadow is lighter (passenger seat has been chopped clean off by previous owner.), I removed the stock 30lbs muffler.
Stock 84 shadow weight = 506lbs
My 84 shadow chpped and screwed = 466lbs
2014 hayabusa stock = 586lbs


Finally as for the rear subframe, if it holds anything its going to be the battery, and some wires all under a custom fender.(But yeah i will need to design it properly)

The way I see it an please correct me if I'm wrong, I should figure out the mono-shock situation before working on subframe and everything else right? Because ultimately the suspension will decide the resting height of the bike right?

Thanks again
 

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My suggestion would be to get hold of a Hayabusa and copy the shock mounts\ rear set up exactly. Playing with frame modifications ain't no joke! You could kill yourself.
 

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irst I want a mono-shock because (however little) it will save weight.
will it though? I mean when all is said and done and the proper reinforcements made how much weight are you actually saving? Its probably better to look at it as an experiment to see if there is an actual weight savings rather than operate under the assumption

I figured about the swing arm, however this bike has a shaft drive system.
That being said do you think I should look for a new swing arm or, strategically redistribute the stress and re-enforce it?
The original design get's it's strength from being a square. by removing the shocks you have removed the two sides of the square. You are unlikely to find a cheap alternative to the shaft drive side, so swapping out the swingarm is not really an option. the problem is the weak side, the non drive side. Now that you have removed the shock it no longer has the resistance to twisting forces and the supporting frame-rail where the shock attached to keep it at bay.
 

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Discussion Starter #6
will it though? I mean when all is said and done and the proper reinforcements made how much weight are you actually saving? Its probably better to look at it as an experiment to see if there is an actual weight savings rather than operate under the assumption

The original design get's it's strength from being a square. by removing the shocks you have removed the two sides of the square. You are unlikely to find a cheap alternative to the shaft drive side, so swapping out the swingarm is not really an option. the problem is the weak side, the non drive side. Now that you have removed the shock it no longer has the resistance to twisting forces and the supporting frame-rail where the shock attached to keep it at bay.
Yes I see what you mean about the weight, It would be wiser to approach it as an experiment.

Yes I do see you the square structural strength you pointed out as well. What if i used the two mounts on each side of the wheel for a brace like structure to simultaneously spreading the stress of the suspension over the whole swingarm as well as strengthening the swingarm....
Something along these lines----
View attachment 9227

or this...
View attachment 9228

Do you think this would stabilize the swing you spoke of?
 

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By the time you brace the existing swingarm and weld on mounting points for a monoshock you will have more weight than just getting a pair of twin shocks.

And where are you going to put all the other stuff that's going to be displaced by the monoshock?
 

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Discussion Starter #8
By the time you brace the existing swingarm and weld on mounting points for a monoshock you will have more weight than just getting a pair of twin shocks.

And where are you going to put all the other stuff that's going to be displaced by the monoshock?
You do have a point hillsy, I want to try to argue that it could depend on what kind of metal I use of the supports but I honestly dont know, either way I really want to see that bike ride on a monoshock suspension.

I know for sure that it weighs much much less than stock already, because as I said previously in the thread the previous owner chopped the rear seat off. I have removed the stock 30lbs muffler, and the air resonance chamber. The new seat i'm making is lighter than the original and/or the one the bike came with, and I'm planning to make a wiring harness from scratch consisting of only the bare necessities.

Most of the things that were where the monoshock is going has either been removed or will be relocated inside the rear fender im going to custom make.

But anyways back to the matter at hand....

The question remains with the braces below, will the bike be stable and not wiggle side to side...??????
mono shock brace.png
mono shock support 2.jpg

If not, what must I DO HELP ME!
 

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The question remains with the braces below, will the bike be stable and not wiggle side to side...??????
No idea - it's kinda like asking how long is a piece of string. The bracing looks OK, but you'll only know for sure once you ride it.

Those pics are of a cantilever set-up. Most monoshock rear ends use a rising rate set-up (Hayabusa included). The location of the shock and the suspension rates are different.

You're in "suck it and see" territory. No one can tell you over the internet if it's going to work or not.

As already advised, it's best to copy the donor bikes' set-up, but it probably wont be possible to copy a rising rate set-up with your swingarm, so you'd be best off finding a cantilever shock (CBR600??).
 

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You just might be able to adapt a Honda Sabre swing arm to that frame. That way you'll get all the links you'll need to install a mono shock. I have a Sabre that I did a few mods on. The shitty air shock was swapped out for a CBR 600 mono shock. Here's the video where I modified and mounted the shock. Fast forward to 10:45 to get the part about the shock.

As I say, this swing arm "might" work on your frame.
 

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Discussion Starter #11
You just might be able to adapt a Honda Sabre swing arm to that frame. That way you'll get all the links you'll need to install a mono shock. I have a Sabre that I did a few mods on. The shitty air shock was swapped out for a CBR 600 mono shock. Here's the video where I modified and mounted the shock. Fast forward to 10:45 to get the part about the shock.


As I say, this swing arm "might" work on your frame.
Are those your videos?
Im subscribed to your channel on youtube I watched the whole build of your bike great work dude lol, I cant believe I never noticed your swing arm was a shaft drive!

I will look into it immediately!
Do you possibly have the measurement of the length, of the part, of the swing arm that goes in between the frame???
 

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I have a 84 Shadow 500 here at the shop that I can measure, and I'll measure my Sabre later today and post the specs here for you.

UPDATE: After looking at the Shadow I have here, no way will the Sabre swing arm go on there. The drive shaft attaches in a different way and the swing arm just won't fit.
 

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Discussion Starter #15 (Edited)
I had a feeling it wouldn't line up or fit :/ but thats ok I think I might order a spare (84 shadow) swingarm and weld the brace Im designing right onto this swingarm and test it to see how it plays out.

Im going to design the brace, model is on solid works run some simulations and get a second opinion from you guys.

I keep this post updated, thank you everyone for your help.
 

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How I would do it. If i HAD to have a monoshock. Look at the xr70 monoshock swing arm. Make a piece that attaches to the stock twin shock mounts that mimics that setup. You will need a front brace going down to the pivot area. Possibly some tabs there, and the whole thing could be unbolted.
 

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Discussion Starter #18
Alright I disappeared because classes started up again and I have been a bit busy anyways....
I mocked up a rough idea of the swingarm brace I had in mind, I made this with the goal of evenly distributing the stress of the suspension through out the swing arm.

This drawing is 2D but the idea is that the farthest reaching bar of the brace loops around the wheel to the other side of the swingarm, while the vertical supports absorb the stress and disperse evenly over the swingarm.

Brace 5 bolted.jpg
the swingarm could be tabbed to bolt the brace in place (for easy removal in the future)

or

Brace 5 welded .jpg
It could be welded along on to the swingarm.

Can anyone comment critique it and give suggestions?
The more I looked at it, the more I felt like the shock should be mounted more horizontally (not completely horizontal), since the weight will be coming from mostly the front (the engine mostly) as apposed to from above.

Maybe I should angle the shock to the loop bar around the wheel so I can channel the stress straight through the shock to the brace?

I'm not sure though....
 

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No, that's pretty much exactly right. I can't find it right now, but try to find pictures of the early BMW R90S AMA superbike race bike. They basically did exactly the design you drew. You really don't need that many braces, typically you see one or two tubes from the diagonal down to the pivot where the shock mounts, and another one on each side from the diagonal to the leg of the swingarm, at 90 degrees.
 

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On your rear shock bolt mount position, it needs to be far higher for correct and safe suspension geometry. The rear shock bolt can't go "under centre" at full squat, if that makes any sense to you.

You should plan on two alternative shock mounting points on the frame or the swingarm to enable chancing the ride height. The front shock bolt mount needs to be very strong and braced. I doubt the Shadow frame is very strong there at all.

The swingarm would have to be bolted into a stable jig if you wanted to weld stuff on.

The brace you have drawn need to be braced transversely with strength, not just in the direction of suspension stresses.

Danger, is my business.
 
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