SuzukiSavage.com - Improved S40 suspension?

barry68v10

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Improved S40 suspension?
04/12/08 at 05:58:00

After exploring a few different options, I've begun pondering an alternate solution and I want some feedback.

I've considered moving the lower shock mount back and down to co-locate it with the rear axle. This would allow a MUCH LONGER shock, and I think you could gain a bunch of extra suspension travel and "dial-in" capability. Anybody thought of or tried this?

Good idea, dumb idea? Thoughts?

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bill67 Serious Thumper Offline old tired Posts: 8517 genoa city wisconsin Gender:	Re: Improved S40 suspension? Reply #1 - 04/12/08 at 06:19:10 I don't think that would give any longer travel.Wouldn't putting a long shock do the same thing .You would be raising the seat height either way.
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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10665 Oklahoma Gender:	Re: Improved S40 suspension? Reply #2 - 04/12/08 at 06:42:34 My sporty have the lower rear shock mounts co-located with the belt/chain adjusters at the very end of the swingarm, just behind the rear axle. It does allow a longer shock (12" at present) and still has a lowered look. For a stock look a 14" shock is required.
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verslagen1 YaBB Moderator ModSquad Offline Where there's a will, I want to be in it. Posts: 28886 L.A. California Gender:	Re: Improved S40 suspension? Reply #3 - 04/12/08 at 08:00:00 yep, the geometry would give it longer travel. moving it back will make the shock seem stiffer. but laying it down will take some of that away. It will take some working out to get it right.
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bill67 Serious Thumper Offline old tired Posts: 8517 genoa city wisconsin Gender:	Re: Improved S40 suspension? Reply #4 - 04/12/08 at 09:04:04 The shock would have a longer travel but the swing arm wouldn't.The straighter up the shock is would be stiffer the way I see it. The flatter it is the would be a leverage,which would make it go up and down easier.I think i see it the opposite that you do.
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Demin Serious Thumper Offline We need more chlorine in the gene pool Posts: 2435 Warren,Ohio Gender:	Re: Improved S40 suspension? Reply #5 - 04/12/08 at 09:08:42 The swingarm swings in an arc.The shock needs to be inline with that arc.
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bill67 Serious Thumper Offline old tired Posts: 8517 genoa city wisconsin Gender:	Re: Improved S40 suspension? Reply #6 - 04/12/08 at 09:32:40 Yes the swing arm swings in an arc,put the shock doesn't have to be inline with the arc.
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Onederer

Ex Member

Re: Improved S40 suspension?
Reply #7 - 04/12/08 at 10:35:00

You'll run outa travel when the tire hits the fender. To get more travel, the bike will have to set higher. Modern link type suspensions have a shock with relativley short travel, but the linkage allows the actual travel to be more than the shock. The progressive 412's seem to be the way to go. Air shocks would be great, but I don't know if they'd clear the strut on the right side. I think the lowering kits for most crusiers just move the lower part of the shock back, like you'r wanting to do, unless someone spends the $$ for shorter shocks. Bottom line, to get more travel from your rear suspension, you'll have to raise the bike. If you wana go 60mph over speed bumps, then just get a DR650. From the kitchen of goodness, the ceramic throne will follow.

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verslagen1 YaBB Moderator ModSquad Offline Where there's a will, I want to be in it. Posts: 28886 L.A. California Gender:	Re: Improved S40 suspension? Reply #8 - 04/12/08 at 12:15:44 For illustration: The greater the angle of the shock to the rear axle travel, the less it will travel. The further out along the swing arm, the less force the shock will see.
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bill67 Serious Thumper Offline old tired Posts: 8517 genoa city wisconsin Gender:	Re: Improved S40 suspension? Reply #9 - 04/12/08 at 12:53:14 You would have to use a longer shock if you did that you would have the same travel,In order to get more travel you have to raise the bike.
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verslagen1

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Re: Improved S40 suspension?
Reply #10 - 04/12/08 at 16:06:21

Engineering 101: Balance of forces.

Let's assume the swingarm is horizontal...
For a certain belt length, the axle is 19.5" from the swingarm pivot.
For the axle hold the rear up, X pounds must be supported by the axle.
We have a spring and a shock absorber to keep the fender off of the tire.
The shock mount on the swingarm is 15.25" from the swingarm pivot.
And a force Y is needed to keep the bike up.
How do you figure out X and Y? By balancing the forces about the swingarm pivot.

19.5 times X is equal to 15.25 times Y
So Y is 1.28 times X

Follow?

Now for the fun part, the above calculated the forces assuming the force on the axle pushed straight up and the shock pushed straight down. Well guess what? the shock pushes at an angle. Der wat dus dat meen? Only some of the force on the shock/spring is applied to the axle. Take a rough measurement of the shock to horizontal, plug that into your calculator and push the sin button. The sin of 51° is .78
1/.78 is 1.28

What a coincidence, that the same ratio of the shock to axle force. 1.28 times 1.28 is the force required by the shock to keep the tire off of the fender. 1.64 For every pound on the wheel, 1.64# is on the shock/spring.

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bill67 Serious Thumper Offline old tired Posts: 8517 genoa city wisconsin Gender:	Re: Improved S40 suspension? Reply #11 - 04/12/08 at 17:10:35 Let us know how it rides when you get that done,verslagen
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steely

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Re: Improved S40 suspension?
Reply #12 - 04/12/08 at 18:13:16

Verslagen is correct. It would require a stouter spring because the increased leverage of the swing arm against the shock would apply more force. I ran into that problem when I lowered the GS. In lowering the rear mounting point, I changed the angle of the shock. Even with a shock designed for a fully dressed Goldwing, I was bottoming out. I had to go back to the original shocks until I could get the new fender (that sat higher) mounted.

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Demin Serious Thumper Offline We need more chlorine in the gene pool Posts: 2435 Warren,Ohio Gender:	Re: Improved S40 suspension? Reply #13 - 04/12/08 at 18:17:51 steely.He just doesn't get it.I gave up.
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steely Senior Member Offline Posts: 325 Tulsa, Oklahoma Gender:	Re: Improved S40 suspension? Reply #14 - 04/12/08 at 18:22:43 Every once in a while I figure that dead horse just will get up...
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