Rear shock length

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I tried searching but couldn't find anywhere on the site or online (but probably just missed it). Anyone know the stock length (eye-to-eye) of the rear shock? I am looking to buy a shorter shock on a budget and one is on e-bay that says 12.5" but I don't know if that's just stock or will get me the extra ground contact I need (5'4" and stretching to the pavement right now).

Thanks
 

DJDixon

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According to the Works Performance website, the stock shock length on the ST1300 (all years/models) is 12.88", bolt center to center unladen. For the ST1100 (all years/models), the stock shock length is 13.38", bolt center to center unladen.

Of course, the spring needs to be matched to the weight of the bike and rider in addition to the overall length, and the rebound / compression must be matched as well. It isn't as easy as finding a shock the same length, unfortunately... :(
 
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Cvillechopper
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Thanks. The shock I'm looking at is for the ST1300 and lists the length as 12.5. Depending on how precise they were with their measurement, it sounds like it could be a shorter shock and would probably have the 1" drop that other listings say they provide.

According to the Works Performance website, the stock shock length on the ST1300 (all years/models) is 12.88", bolt center to center unladen. For the ST1100 (all years/models), the stock shock length is 13.38", bolt center to center unladen.

Of course, the spring needs to be matched to the weight of the bike and rider in addition to the overall length, and the rebound / compression must be matched as well. It isn't as easy as finding a shock the same length, unfortunately... :(
 

ST Gui

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I'm lousy at geometry but a 1" drop in height sounds excessive for a shock that's only .38" shorter than factory. Of course raising the fork tubes in the triple clamps slightly would lower the front of the bike while also preserving the factory handling.
 

Kevin_56

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I'm lousy at geometry but a 1" drop in height sounds excessive for a shock that's only .38" shorter than factory.
The shock mounting point is between the pivot point and the axle. If the mounting point was exactly in the middle, then a .38" shorter length would change the axle .76". Compound that in the shock is also at an angle and that makes the change at the axle a little
less.
 
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Cvillechopper
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That was kind of my thought except, the bottom of the shock appears to mount slightly forward of the mid-point between axle and pivot. It's also at an angle which I believe increases the impact of a small change to the end movement by about 1 1/2 to 3 times depending on the angle of the shock. Without exact measurements I can't be certain the amount but it's in the ballpark.

The shock mounting point is between the pivot point and the axle. If the mounting point was exactly in the middle, then a .38" shorter length would change the axle .76". Compound that in the shock is also at an angle and that makes the change at the axle a little
less.
 

ST Gui

240Robert
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Cvillechopper said:
Without exact measurements...
This was kind of my thought. Again geometry is a foreign language to me. My only experience with modifying it for height was putting 5 or 6" slugs in my 305's forks thinking in it would raise the front end a bunch. Turn out it was only raised maybe 1.5". And it gave me a hellacious high-speed wobble that tore a patch out of the seat.

The rear shock/swing arm is a different situation of course. I'd like to see some close measurements and the results. Where would the delta be measured? Between the ground and where?
 
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Cvillechopper
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Good point. Cleanest and most exact measurement would be using a solid body panel. Since the goal is to lower the seat height, I'd probably measure from the ground to the center of the front bolt for the side cover.


This was kind of my thought. Again geometry is a foreign language to me. My only experience with modifying it for height was putting 5 or 6" slugs in my 305's forks thinking in it would raise the front end a bunch. Turn out it was only raised maybe 1.5". And it gave me a hellacious high-speed wobble that tore a patch out of the seat.

The rear shock/swing arm is a different situation of course. I'd like to see some close measurements and the results. Where would the delta be measured? Between the ground and where?
 
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What is the difference in unladen length between the st1100 shorter Works shock and the stock shock? I know the Works shorter shock lowers the seat 1 1/4 inches. That should give you a rough idea.
 

ST Gui

240Robert
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The Works application chart shows the stock 1100 shock length eye-to-eye at 13.38" and the 'short shock' replacement for it at 12.75" for a delta of .63".

Without having the exact bike lengths and angles (and the ability to do anything with them LOL) .63" dropping the seat 1.25" feels more correct than .38" dropping the seat 1".

So if Cville has found a shock that measures 12.5" then a delta of Works' 1300 spec of 12.88 is .38". But the rear end geometry may not be the same as the 1100. If it were I'd guess the seat height to drop less than 1". That's at best just a WAG.

Someone here must have already affected a lower seat height on a 1300 by way of a shorter shock. Bueller?
 
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About 3/4 ". That can be a lot. Can you shorten it a little more with lower aspect ratio tires? That and Pee Wee Herman boots and you're set!
 

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I think I just may have to pull the rear shock to measure it. The weather is right for spinning wrenches...
I have a spare stock shock I just measured....center to center of mounting holes is 12 7/8" or 12.875". Pretty close to the 12.88 already referenced.
 
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Cvillechopper
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Thanks. Saves me from having to pull the shock. Probable going to try and get the rest of the measurements necessary to calculate the seat drop realized by x amount of shock length reduction. Mainly just want to see if I can still do it.

I have a spare stock shock I just measured....center to center of mounting holes is 12 7/8" or 12.875". Pretty close to the 12.88 already referenced.
 
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