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-   -   2.2 tires and pinion swap (http://www.rcuniverse.com/forum/redcat-racing-support-427/11411725-2-2-tires-pinion-swap.html)

Johnathond22 02-15-2013 10:35 PM

2.2 tires and pinion swap
 
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Has anyone changed their tires on Volcano EPX pro with a little bit bigger tire and had to swap pinion to correct gear ratio? I ran the math and replacing my 21t pinion with 17t will return my truck to near stock ratio with my new tires. If I go down to 15t will the extra torque help or hurt? I don't want to burn up the motor but also don't want to destroy the drive train. I just cut these 2.2 slingers to fit on 2.8 rim and noticed an instant loss of power.

Johnathond22 02-20-2013 06:59 AM

RE: 2.2 tires and pinion swap
 
This is the calculation of the gear tire swap to 4.5 slingers and 17t replacement....

<div>Differential Ratio: 2.23:1</div><div>Transmission Ratio: 1:8.9</div><div>Other Ratio: 1</div><div>Spur Tooth Count: 64</div><div>Pinion Tooth Count: 17</div><div>Total Voltage: 7.40</div><div>Motor KV: 3300</div><div>Tire Diameter (inches): 4.5</div><div>Tire Ballooning (inches): 0</div><div>Motor Current Draw: 30</div><div>Motor Coil Resistance: 0</div><div>Spur/Pinion Ratio: 3.76 : 1</div><div>Total Ratio: 8.39529 : 1</div><div>Tire Circumference (inches): 14.14 inches (359.08 mm)</div><div>Rollout: 1.68:1</div><div>Total Motor Speed: 24420 RPM</div><div>Vehicle Speed: 38.94 mph (62.55 km/h)</div><div>Effective KV Value: 3300</div><div>KT constant: 0.41 oz-in/A</div><div>Motor Torque: 0.06 ft-lbs</div><div>Final Torque: 0.54 ft-lbs</div>Final Power: 222 watts (0.3 HP)

Johnathond22 02-20-2013 07:01 AM

RE: 2.2 tires and pinion swap
 
This would be calculation of 15t, less speed but more torque, not sure if this would cause motor issues. Does gearing too low put strain on motor and esc or only reduce speed and add stress to drive train...

<div>Differential Ratio: 2.23:1</div><div>Transmission Ratio: 1:8.9</div><div>Other Ratio: 1</div><div>Spur Tooth Count: 64</div><div>Pinion Tooth Count: 15</div><div>Total Voltage: 7.40</div><div>Motor KV: 3300</div><div>Tire Diameter (inches): 4.5</div><div>Tire Ballooning (inches): 0</div><div>Motor Current Draw: 30</div><div>Motor Coil Resistance: 0</div><div>Spur/Pinion Ratio: 4.27 : 1</div><div>Total Ratio: 9.51467 : 1</div><div>Tire Circumference (inches): 14.14 inches (359.08 mm)</div><div>Rollout: 1.49:1</div><div>Total Motor Speed: 24420 RPM</div><div>Vehicle Speed: 34.36 mph (55.19 km/h)</div><div>Effective KV Value: 3300</div><div>KT constant: 0.41 oz-in/A</div><div>Motor Torque: 0.06 ft-lbs</div><div>Final Torque: 0.61 ft-lbs</div>Final Power: 222 watts (0.3 HP)

nitrosportsandrunner 02-20-2013 08:31 AM

RE: 2.2 tires and pinion swap
 
gearing too low will cause the motor to run at near max RPMs too often.

But given the size of your tires going down to a 17t shouldnt be an issue.

those tires look awsome on the volcano!

Johnathond22 02-20-2013 09:27 AM

RE: 2.2 tires and pinion swap
 
Thanks for info and as for the tires, I really like them as well. They really do perform well for the Volcano. The rubber is quite a bit softer so traction is great.

Did you ever get to bash test the skid? I never heard back from Nate, I assume it went well. I actually made two more for Volcano owners here locally and will start a Stampede bumper tomorrow night. It will be interesting as there are alot more bends. I am also making the bigger dogbones. I had to order a bunch of hex pins to use as the ends. Does your Tornado run the same dogbone as volcano (89.5mm/90mm)? I'll send you a set when done.

Eshore 02-20-2013 02:20 PM

RE: 2.2 tires and pinion swap
 
Nice looking truck!

Johnathond22 02-20-2013 02:48 PM

RE: 2.2 tires and pinion swap
 
Thanks, I have been having fun with the different mods that can be done with these RC trucks and its interesting to attempt to build my own parts and accesories. I actually built the bumper and skid you see from Aluminum and will be attempting to make dogbones and A-arms next. Definatley a cool hobby.

nitrosportsandrunner 02-20-2013 03:10 PM

RE: 2.2 tires and pinion swap
 

Quote:

ORIGINAL: Johnathond22

Thanks for info and as for the tires, I really like them as well. They really do perform well for the Volcano. The rubber is quite a bit softer so traction is great.

Did you ever get to bash test the skid? I never heard back from Nate, I assume it went well. I actually made two more for Volcano owners here locally and will start a Stampede bumper tomorrow night. It will be interesting as there are alot more bends. I am also making the bigger dogbones. I had to order a bunch of hex pins to use as the ends. Does your Tornado run the same dogbone as volcano (89.5mm/90mm)? I'll send you a set when done.
it uses 87mm....tho 87.5mm would probly be better (as I find there is more play than needed)
but the thickness and the ends are the same as on the volcano.
Naturally the lightning and tornado dont break driveshafts as often as the volcano, due to the smaller tires.

with the crawler tires you put on yours, some upgrade dogbones will help alot.


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