Top Speed of Belt Drive Chinese 4 Strokes

Mike St

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DT did you know that GPS speed can be off on the high side by 4-5mph?
Don't believe you're getting 32mph with this setup. With 9t drive sprocket
and 36T rear sprocket, and 5:1 gear box, your max speed at 6800 rpm is: 26.2 mph.
6800 divided by 5x4 x 6.78 x 60 all divided by 5280= 26.2
With a 10T drive sprocket, it would go to about 29mph.
 

DieselTech

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DT did you know that GPS speed can be off on the high side by 4-5mph?
Don't believe you're getting 32mph with this setup. With 9t drive sprocket
and 36T rear sprocket, and 5:1 gear box, your max speed at 6800 rpm is: 26.2 mph.
6800 divided by 5x4 x 6.78 x 60 all divided by 5280= 26.2
With a 10T drive sprocket, it would go to about 29mph.
Yeah I figure it might be off some, I used my phone GPS & typically its can be off 1-3mph in either direction. With my friends side by side riding next to me, top speed on my bike by his speedo was 31mph. Its definitely low geared, & can climb trees. I personally need to get the 80tooth & 90tooth pulleys & do some testing, I think the 90tooth might be perfect.
 

Karl Snarl

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Yeah I figure it might be off some, I used my phone GPS & typically its can be off 1-3mph in either direction. With my friends side by side riding next to me, top speed on my bike by his speedo was 31mph. Its definitely low geared, & can climb trees. I personally need to get the 80tooth & 90tooth pulleys & do some testing, I think the 90tooth might be perfect.
Also depends on your gps system. Some of them are quite accurate, if you are willing to spend more than a few bucks.
 

DieselTech

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Also depends on your gps system. Some of them are quite accurate, if you are willing to spend more than a few bucks.
I think I'm going to order another grubee engine & tranny, & a shift from them as well. I decided to shift kit my micargi rover, since it is so low geared. Might not be as reliable, with shift kit but idk, cause I've never had 1 or been around them.
 

Mike St

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Fabulous. Buy the 4:1 belt drive, and if you use 10T drive sprocket and
a 41T wheel sprocket you hit a sweet spot at 32mph. And the belt
drive will have bearings!!!
 

Sidewinder Jerry

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DT did you know that GPS speed can be off on the high side by 4-5mph?
Don't believe you're getting 32mph with this setup. With 9t drive sprocket
and 36T rear sprocket, and 5:1 gear box, your max speed at 6800 rpm is: 26.2 mph.
6800 divided by 5x4 x 6.78 x 60 all divided by 5280= 26.2
With a 10T drive sprocket, it would go to about 29mph.
Assuming 26" tires are being used.

Sidewinder Jerry's mph speed formula

(RPM x Wheel Diameter x π)÷(1056 × Total Reduction)=MPH

(6,800×26×π)÷(1,056×(5×(36÷9)))=26.2989385016

(6,800×26×π)÷(1,056×(5×(36÷10)))=29.2210427796
 

Cannonball3

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To be a bit more accurate use the tires circumference. Its easy to do with the roll method of making a mark on the tire and floor rolling one revolution making a second mark and measuring the distance. Tires of the same size will vary.
 
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