Araz
.020 Over
- Joined
- Jun 7, 2021
- Messages
- 22
- Ride
- Rocket III Touring
This is a long read. Stems from the fact that i found tach installation somewhat tricky and decided to do math instead. I've done this because I didn't need tach as such, I needed to know optimal speed for each each gear range
Equation is simple > MPH = (Engine RPM * Radius) / (Final Gear Ratio * 168)
Triumph manual states following gear ratios:
1st 2.929
2nd 1.947
3rd 1.435
4th 1.16
5th 0.964
Primary Drive 1.034
Secondary Drive 1.043
Final Drive 2.846
Radius in the equation stands for the Tire Radius (not just wheel). Using tire size calculator, factory 180/70 R16 (rear) has a tire diameter of 25.9 inches, i.e the radius of 12.95 inches
Final Gear Ratio is the product of gear you are driving at and all the gears on the path to tire. So if you are travelling at 5th gear, Final Gear Ratio would be 5th * Primary * Secondary * Final = 0.964 * 1.034 * 1.043 * 2.846
There was a post earlier in the thread with a chart of RPM vs Speed (corrected mph values) at presumably the fifth gear (attachment 1). I used this chart as a QC to calculations, so i could then calculate speeds for other gears as well
To my surprise when i calculated speed for rpms used in said chart (att 1) the difference started creeping up to 5mph at 90mph and onwards (attachment 2 > speed on the chart vs calculated (as per manual) speed). I wasn't sure what started causing this diff since there shouldn't be uncertainties in tire radius and gear ratios..Nevertheless, I was decisive to match the calculated values, so I used 5th gear ratio, tire radius and rpm as known parameters, and solved for the product of primary, secondary and final drive ratios..resultant calculation was spot on (second rightmost column) with the numbers shown in the chart in att 1.
Finally, using the knowledge of identified true ratios, i have calculated the speed for all the remaining gears..
I you'd derestricted Touring with Power Tripps tune, your engine max RPM should increase from 4500 to 6000 rpm. Also, if you believe torque and hp lines from his chart (attachment 4) it probably would makes sense to change gears roughly at 5000 rpm(for best acceleration)..As per the chart in att 3, if you think that 5000 rpm is ok, gear changes should happen as following:
1st gear - 40mph
2nd gear - 60 mph
3rd gear - 80 mph
4th gear - 100 mph
Happy to hear any feedback and make adjustments where necessary
Equation is simple > MPH = (Engine RPM * Radius) / (Final Gear Ratio * 168)
Triumph manual states following gear ratios:
1st 2.929
2nd 1.947
3rd 1.435
4th 1.16
5th 0.964
Primary Drive 1.034
Secondary Drive 1.043
Final Drive 2.846
Radius in the equation stands for the Tire Radius (not just wheel). Using tire size calculator, factory 180/70 R16 (rear) has a tire diameter of 25.9 inches, i.e the radius of 12.95 inches
Final Gear Ratio is the product of gear you are driving at and all the gears on the path to tire. So if you are travelling at 5th gear, Final Gear Ratio would be 5th * Primary * Secondary * Final = 0.964 * 1.034 * 1.043 * 2.846
There was a post earlier in the thread with a chart of RPM vs Speed (corrected mph values) at presumably the fifth gear (attachment 1). I used this chart as a QC to calculations, so i could then calculate speeds for other gears as well
To my surprise when i calculated speed for rpms used in said chart (att 1) the difference started creeping up to 5mph at 90mph and onwards (attachment 2 > speed on the chart vs calculated (as per manual) speed). I wasn't sure what started causing this diff since there shouldn't be uncertainties in tire radius and gear ratios..Nevertheless, I was decisive to match the calculated values, so I used 5th gear ratio, tire radius and rpm as known parameters, and solved for the product of primary, secondary and final drive ratios..resultant calculation was spot on (second rightmost column) with the numbers shown in the chart in att 1.
Finally, using the knowledge of identified true ratios, i have calculated the speed for all the remaining gears..
I you'd derestricted Touring with Power Tripps tune, your engine max RPM should increase from 4500 to 6000 rpm. Also, if you believe torque and hp lines from his chart (attachment 4) it probably would makes sense to change gears roughly at 5000 rpm(for best acceleration)..As per the chart in att 3, if you think that 5000 rpm is ok, gear changes should happen as following:
1st gear - 40mph
2nd gear - 60 mph
3rd gear - 80 mph
4th gear - 100 mph
Happy to hear any feedback and make adjustments where necessary