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Discussion Starter #1 (Edited)
My general observations with shims vs Coop45 machined sheave. Hopefully this will help others understand the effects these mods have on their machines before making their decision on what mod is best for them. Results may vary based on numerous variables. Belt and sheave condition greatly influences the final numbers.

Stock
2.45:1

-1mm shim
2.65 to 2.70:1
Aprox 8-10% reduction in initial ratio, around 2.5 mph top speed loss

-1.5mm shim
2.75 to 2.8:1
Aprox 12-14% ratio reduction, around 4 mph top speed loss

-Coop45 sheave, no shim
2.9:1
Aprox 18.5% ratio reduction, equivalent to 2mm of shims but no top speed loss

-Coop45 sheave, with 0.5mm shim
3:1
Aprox 22.5% ratio reduction, equivalent to 2.5mm worth of shims but with only 1.25 mph top speed loss.



Anyone else feel free to post your own results
 

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Good summary, thanks for taking the time to post up the info. I had similar results, and definitely like the Mod 3 with .5mm shim.
 

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Discussion Starter #6 (Edited)
Good summary, thanks for taking the time to post up the info. I had similar results, and definitely like the Mod 3 with .5mm shim.
Thanks for the positive feedback.
How did you manage a ratio of 3.19:1?
 

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Thanks for the positive feedback.
How did you manage a ratio of 3.19:1?
Lol, its supposed to say 3.10, I hadn't even checked that typo haha :grin2:
 

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Discussion Starter #8
Anyone else have any experiences or data to share?
 

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Yeah, meant to post on this but got busy and forgot.

Coop45 Mod 3, machined primary with .7mm shim and a purple spring on the secondary. I get roughly 3.1:1 ratio. Love the low end torque and really love the increased engine braking. I do not care if I'm missing a slight bit of top end speed, from the added .7mm shim, as no where I ride that matters.
 

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Discussion Starter #10 (Edited)
Yeah, meant to post on this but got busy and forgot.

Coop45 Mod 3, machined primary with .7mm shim and a purple spring on the secondary. I get roughly 3.1:1 ratio. Love the low end torque and really love the increased engine braking. I do not care if I'm missing a slight bit of top end speed, from the added .7mm shim, as no where I ride that matters.
Agreed. All great benefits to this awesome clutch set up! Thanks for posting.

With 0.5 mm shim I'm actually about 3.05:1
I felt the extra 0.05:1 ratio wasn't worth the mention in my original post
 

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I really appreciate this thread, so thank you! I'm getting ready to send my sheave to coop. I have 1.5mm of shim and a gold spring. And While this was great at first with my heavy 28x10 Blackwater evos, I'm now looking for more grunt down low.
 

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Has anyone tried the coop mod , shim and slugs. I’ve heard the slug mods add noticeable performance gains.
 

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Discussion Starter #13
I really appreciate this thread, so thank you! I'm getting ready to send my sheave to coop. I have 1.5mm of shim and a gold spring. And While this was great at first with my heavy 28x10 Blackwater evos, I'm now looking for more grunt down low.
Thanks. Your more then welcome to post your results here once everything is said and done.
 

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I myself also have the Coop45 with the .5 shim and it’s somewhere around 3.1 to 1. Haven’t had the chance to play in the mud with yet ?. Does anyone run the white Epi spring?
 

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woodsman307- No I'am running a set up close to yours and I'm using the purple spring and happy with it's performance. But I'm running the stock 25" wheels.
 

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I myself also have the Coop45 with the .5 shim and it’s somewhere around 3.1 to 1. Haven’t had the chance to play in the mud with yet ?. Does anyone run the white Epi spring?
I run a higher pulley ratio with 26.5" tall tires and the purple spring works great.
To know if the white spring will benefit you, you will have to try it for your riding style in you local trail conditions.
I found the purple spring is best for me as there needs to be the ability to have something slip in the drive line between the primary pulley and the wheel to prevent something from breaking out on the trail, like an axle. Every now and then I hear a faint chirp from the belt, like when landing a jump with too much throttle. One time I broke a rear axle doing this and it was a long way back to the truck, and if you haven't tried to load a grizz into the back of a truck with only one axle pulling, it is a '_itch'.
Generally those riding mud bogs with bigger/stronger axles than stock use the heavier than purple spring(s).
 

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Ok sounds good. I have 29.5x10-12 terms on mine. So with that being said my main riding is mud.
 

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Discussion Starter #18
Ok sounds good. I have 29.5x10-12 terms on mine. So with that being said my main riding is mud.
Sounds like you got her clutch just right for your requirements.
 

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I myself also have the Coop45 with the .5 shim and it’s somewhere around 3.1 to 1. Haven’t had the chance to play in the mud with yet ?. Does anyone run the white Epi spring?
I run a higher pulley ratio with 26.5" tall tires and the purple spring works great.
To know if the white spring will benefit you, you will have to try it for your riding style in you local trail conditions.
I found the purple spring is best for me as there needs to be the ability to have something slip in the drive line between the primary pulley and the wheel to prevent something from breaking out on the trail, like an axle. Every now and then I hear a faint chirp from the belt, like when landing a jump with too much throttle. One time I broke a rear axle doing this and it was a long way back to the truck, and if you haven't tried to load a grizz into the back of a truck with only one axle pulling, it is a '_itch'.
Generally those riding mud bogs with bigger/stronger axles than stock use the heavier than purple spring(s).
why fight it into the bed of the truck? Just sling a rope from stake bed hole to stake bed hole and let the winch do the work. Why risk injury? I'm thinking about mounting a permanent ring at front/center just in case it's ever needed.
 

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I would have but I didn't bring an extra rope! :)
 
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