UPDATE: Excel tool updated after removing a copy-paste formula error. Thanks to Mark Barone!

Tired of blowing up your motor or screwing up gears in your RC vehicle ? Well it's better to start good and do the things the right way!.

You need to understand the Physics involved here. This excel workbook will help you choose what pinion gear & spur combinations you need with a particular battery voltage & transmission gear ratio of your RC vehicle to achieve a desired speed (mph).

Now you won't have to burn your money before you know if it really works! How cool is that ?

RC Cars & RC Trucks

This workbook has been tested on RC On-Road cars and Off-Road RC Trucks & Truggies like stampeed, rustler, Traxxas Slash 2wd, Traxxas Slash 4x4 and Traxxas Summit.

It works perfectly well for any other RC vehicle as well. Principles are the same!

Pinion Gear & Spur Selector

First you need to

• Specify your Motor Kv
• Specify Transmission Gear Ratio
• Specify Tire outer Diameter

Now you can select the best suited combination in two ways

Starting from Battery voltage perspective

1. Select battery voltage from the Auto Filter
2. Select desired speed in MPH or KMH range. e.g. Auto-Filter -> "greater than" -> 50 mph

Starting from Desired Speed perspective

1. Select desired speed in MPH or KMH range. e.g. Auto-Filter -> "greater than" -> 50 mph
2. Select battery voltage as desired. May be you already have that pack?

Now you'll see a list of all combinations which are recommended by Traxxas in their Owner's Manual. You can choose any option you think you would like to use. Perhaps you already have some parts for those combinations or you can easily find them in your local Hobby store.

Some of the combinations are only for LiPo and others are good for NiMh and LiPo both. It just means that certain combinations are not recommended having a NiMh in your battery compartment due to low current rate.

Electric Motor / ESC Safety Zone vs Pinion & Spur Gear combination

Please follow below precautions while you chose a combination for a particular Kv motor.

• Pay attention to "Work Efficiency" that it should never be below 90% or your motor will almost all the time run at peak RPM
• Pay attention to "Work Ratio" that
  • It should not be too high or it will heat up your setup causing a possible burn out
  • It should not be lower than -1 or your motor will exclusively run on Peak RPM wearing it the most

Download Pinion & Spur Gear Selection Excel workbook

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