anyone know the actual ratio numbers when changing from a 8 to 7 tooth driver.
Can't find it anywhere
Can't find it anywhere
Gear ratio going from 8 to 7 tooth drivers
- Thread starter WyoBoy1000
- Start date
What ratio numbers are you looking for?
With 19/50 gearing and 8 tooth drivers you are theoretically geared for 78 mph
With 19/50 gearing and 7 tooth drivers you are theoretically geared for 68 mph
With 20/49 8 tooth is 84 mph
With 20/49 7 tooth is 74 mph
These are just baseline numbers and don't come out 100% because clutching throws a nasty wrench in that equation.
With 19/50 gearing and 8 tooth drivers you are theoretically geared for 78 mph
With 19/50 gearing and 7 tooth drivers you are theoretically geared for 68 mph
With 20/49 8 tooth is 84 mph
With 20/49 7 tooth is 74 mph
These are just baseline numbers and don't come out 100% because clutching throws a nasty wrench in that equation.
its right at 7% reduction
Here is a really cool interactive spread sheet that does all the calculations for you. Just type in your numbers to see the effective changes.
Special thanks to arcticchat members Nick and firecatsrt for posting this!
Special thanks to arcticchat members Nick and firecatsrt for posting this!
here is what I'm looking for
I want to be at the same gear ratio of 2.45-2.5 on a 8 tooth, so if I go with a 7 tooth what would I put in, stock 12 gears ? 2.33= what that equal.
I'm looking for a number as in a calculating number
if I ran 2.45 gearing for a 8 tooth the ratio is 2.45 now if it is a 7% reduction.
2.45x.07=.1715 add that up to get 2.6215
so 7 tooth with 2.45 gears is 2.62
so stock 12 gears 2.33 if I remember right
2.33x.07=.1631 + 2.33 =2.4931
7 tooth with 2.33 =2.4931
Is this 7% number accurate?
I want to be at the same gear ratio of 2.45-2.5 on a 8 tooth, so if I go with a 7 tooth what would I put in, stock 12 gears ? 2.33= what that equal.
I'm looking for a number as in a calculating number
if I ran 2.45 gearing for a 8 tooth the ratio is 2.45 now if it is a 7% reduction.
2.45x.07=.1715 add that up to get 2.6215
so 7 tooth with 2.45 gears is 2.62
so stock 12 gears 2.33 if I remember right
2.33x.07=.1631 + 2.33 =2.4931
7 tooth with 2.33 =2.4931
Is this 7% number accurate?
12.5 % reduction by my simple math going from 8 tooth to 7 tooth 3.0 pitch.
Some of it comes down to available sprocket sizes also.
According to the calculator the closest you could get to a 20/49 8 tooth set up using 7 tooth drivers would be,
22/48 (2.18 ratio) with 7 tooth drivers would be approx 1.26 mph slower at 1 to 1 clutch shift out.
22/47 (2.13 ratio) with 7 tooth drivers would be approx .3 mph faster at 1 to 1 clutch shift out.
I would think that the 22/48 7 tooth would be just about ideal on a mountain sled, if your goal is to stay near the 20/49 8 tooth drive ratio.
According to the calculator the closest you could get to a 20/49 8 tooth set up using 7 tooth drivers would be,
22/48 (2.18 ratio) with 7 tooth drivers would be approx 1.26 mph slower at 1 to 1 clutch shift out.
22/47 (2.13 ratio) with 7 tooth drivers would be approx .3 mph faster at 1 to 1 clutch shift out.
I would think that the 22/48 7 tooth would be just about ideal on a mountain sled, if your goal is to stay near the 20/49 8 tooth drive ratio.
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Some of it comes down to available sprocket sizes also.
According to the calculator the closest you could get to a 20/49 8 tooth set up using 7 tooth drivers would be,
22/48 (2.18 ratio) with 7 tooth drivers would be approx 1.26 mph slower at 1 to 1 clutch shift out.
22/47 (2.13 ratio) with 7 tooth drivers would be approx .3 mph faster at 1 to 1 clutch shift out.
I would think that the 22/48 7 tooth would be just about ideal on a mountain sled, if your goal is to stay near the 20/49 8 tooth drive ratio.
just for learning purposes , if you had 8 tooth @ 2.52 pitch they measure 22.68 cir. 7 tooth 3 inch pitch 21 inch. 22.68-21/22.68 gives 7.4%reduction. Drivers never measure the teeth x pitch and Avids run even smaller. I have the actual Circumference written down at the office and recall them near 20.5 cir. I run 2.4 gearing with my 7 tooths and am right at 1-1 ratio clutch shift on a Doo w/ 3 inch
Your math is right. We find the poo drivers are a little over pitched. I'm sure that Wyoboy is going from 8 tooth 3.0 pitch to 7s.
7÷8 = .875 meaning 7 tooths are 87.5% the size of 8s, giving 12.5% reduction.
If he's running 2.45 gearing a 12.5% reduction equals 2.14375. Seems a little steep to me but the math works.
a 12.5% reduction would read as a gear ratio of 2.756.
2.45x0.125=.30625 then you add that number to the 2.45 + .30625 = 2.756
So if 12.5% is correct then
21/49 = 2.333
2.333x.125=0.291625
0.291625+2.333=2.624625
So to change drivers with a stock 12 setup from 8 to 7 tooth it would be like gearing down to 2.62. Way to low
But to go from a 21 up to a 24 (8 tooth) its a 14.29% increase. So going down its a 12.5% decrease, this is a little confusing, lol.
But what is correct 7% 12.5% ???
Obviously since this is a cat it would be going from a 8x3.0 to a 7x3.0 tooth and pitch
which technically 8x3 = 24 7x3=21 percentage decrease from 24 - 21 = 12.5% But I'm not a 100% thats how it works
2.45x0.125=.30625 then you add that number to the 2.45 + .30625 = 2.756
So if 12.5% is correct then
21/49 = 2.333
2.333x.125=0.291625
0.291625+2.333=2.624625
So to change drivers with a stock 12 setup from 8 to 7 tooth it would be like gearing down to 2.62. Way to low
But to go from a 21 up to a 24 (8 tooth) its a 14.29% increase. So going down its a 12.5% decrease, this is a little confusing, lol.
But what is correct 7% 12.5% ???
Obviously since this is a cat it would be going from a 8x3.0 to a 7x3.0 tooth and pitch
which technically 8x3 = 24 7x3=21 percentage decrease from 24 - 21 = 12.5% But I'm not a 100% thats how it works
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It seems like you would have to run 21/47 to get to around the 2.5 ratio I want
21/47=2.238
2.238x(12.5%) .125= 0.279
2.238+.279= 2.52
So I need a belt drive that come in around 2.22 to 2.3
21/47=2.238
2.238x(12.5%) .125= 0.279
2.238+.279= 2.52
So I need a belt drive that come in around 2.22 to 2.3
With 21/47 gearing you will be running a 3:1 belt to ride ratio.
With 21/47 gearing you will be running a 3:1 belt to ride ratio.
If I run 21/47 with 7 tooth it would be about the same ratio as running a 20/50 with a 8 tooth. So it would be geared down slightly from the stock 12 2.33 to 2.52.
The stock 14 gears run a higher overdrive than this would
2.2 to 2.35 seems to be where a lot of the poo guys gear to when running 7 tooth 3.0 drivers. So you understand and calculated correct in my book.
I ordered 2.33 from tki to run on my 13 with a 156x3 with 7 tooth drivers.
I think the gear ratios people are running on these things to save belts are rediculous. I ran 21/42 with 3.0 pitch 8s for years and years on a mountain cat without ever burning belts.
IMO if you gear to low you never load the motor and lose performance
Agreed, plus the design of the clutch weights didn't change. The gear down was cats bandaid for a bad setup and I have yet to see performance gains from any gear down. Longer belt life maybe but they never felt right.
Does anyone know the measurements of a 8 and 7 tooth,
3in pitch.
8 tooth.
3x8=24" circumference. ÷ 3.14 = 7.6" dia.
3x7=21" circumference. ÷ 3.14 = 6.6"dia.
12.5% smaller
8 tooth.
3x8=24" circumference. ÷ 3.14 = 7.6" dia.
3x7=21" circumference. ÷ 3.14 = 6.6"dia.
12.5% smaller
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Is that the actual measurement
I did not measure but, math doesn't lie. Un less my math is wrong, the measurement is close to those numbers.
3in pitch means 3inches between paddles, does that not also mean 3inches on center for the tooth on the driver? If so then....
3×8÷3.1416
=7.6394194041
3×7÷3.1416
=6.6844919786
3in pitch means 3inches between paddles, does that not also mean 3inches on center for the tooth on the driver? If so then....
3×8÷3.1416
=7.6394194041
3×7÷3.1416
=6.6844919786
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