Does anybody know the ratio of the primary drive in the Blaster? If not, does anybody have one apart that could count the teeth on each gear for me? I'd like it for some calculations. I'm thinking it must be in the range of 2.5:1 or so??
Primary drive ratio?
- Thread starter doc_speeder
- Start date
Blaster 89
1st 34/11 (3.091)
2nd 31/14 (2.214)
3rd 25/15 (1.667)
4th 20/16 (1.250)
5th 19/18 (1.056)
6th 19/21 (0.905)
1st 34/11 (3.091)
2nd 31/14 (2.214)
3rd 25/15 (1.667)
4th 20/16 (1.250)
5th 19/18 (1.056)
6th 19/21 (0.905)
Stock final drive ratio (sprockets) is 3.08.
Check out this nifty chart on Renthal's site:
Renthal - We Build Championships
Check out this nifty chart on Renthal's site:
Renthal - We Build Championships
Not sure where that comes from, 40 divided by 13 is 3.08
and 3.08 divided by .905 (yz otis' sixth gear) is 3.40
Maybe there are different trans ratios for diff years
and 3.08 divided by .905 (yz otis' sixth gear) is 3.40
Maybe there are different trans ratios for diff years
Thanks dude. That's the number I was looking for. The other ratios you other guys put up were the final drive and trans ratios. Thanks for coming out though ...hehe
I bet thats the ratio between the crank output and trans input gears - primary reduction.....
For those of you stumped, I was looking for the reduction from the crank to the trans input shaft. I'm calculating theoretical top speeds with different final drives and tire sizes at 8500 RPM
So then, with stock gears and 20" tires, the calculation goes like this.
1) 20"x 3.14 = 62.8" circumference / 12" = 5.23 ft per tire revolution
2) 8500 rpm / 3.227 / .905 / 3.08 x 60 mins x 5.23 ft / 5280 ft/mile = 56.16 mph. Not too impressive but it is a way to figure out what gearing/tire size you need for your target mph. Not a big deal for me, as I'm usually in 3rd-5th gear max on the trails. But interesting anyway.
Circumferences for various tire sizes (assuming published size is close to actual size, not always a safe assumption)
18" - 56.52"
20" - 62.8"
22" - 69.08"
Gear ratios for various combinations:
13/40 = 3.08
13/39 = 3.00
14/38 = 2.71
etc, etc, etc
So a 22" tire with 14/38 gearing, assuming enough motor to pull 8500 rpm would have a theoretical top speed of about 70.1 mph. Pretty good improvement over stock.
Yes, I'm bored...
So then, with stock gears and 20" tires, the calculation goes like this.
1) 20"x 3.14 = 62.8" circumference / 12" = 5.23 ft per tire revolution
2) 8500 rpm / 3.227 / .905 / 3.08 x 60 mins x 5.23 ft / 5280 ft/mile = 56.16 mph. Not too impressive but it is a way to figure out what gearing/tire size you need for your target mph. Not a big deal for me, as I'm usually in 3rd-5th gear max on the trails. But interesting anyway.
Circumferences for various tire sizes (assuming published size is close to actual size, not always a safe assumption)
18" - 56.52"
20" - 62.8"
22" - 69.08"
Gear ratios for various combinations:
13/40 = 3.08
13/39 = 3.00
14/38 = 2.71
etc, etc, etc
So a 22" tire with 14/38 gearing, assuming enough motor to pull 8500 rpm would have a theoretical top speed of about 70.1 mph. Pretty good improvement over stock.
Yes, I'm bored...
Dont forget about the rider weight.
70.1 mph with a 100 lb rider but how fast with a 300 lb rider. LOL
Thanks, this helps clear up a big issue for me. Rep points, simple math, but good info.
Then also gotta take into effect frictional forces and aerodynamics. (j/k)
Then also gotta take into effect frictional forces and aerodynamics. (j/k)
Lol, even though it is simple math... aparently I can't do it.
I plugged in for 22" tires and 14/40 gears. Ended up with 5. something after plugging my numbers into line 2.
Yes, those will affect top speed, but not the calculation for theoretical top speed. 8500 rpm will give you the speed you calculate regardless of friction or aero forces. The factor will be that you may not have the motor to reach that 8500 rpm due to the friction and aero.
Similar threads
