Calculate gear ratios and theoretical speeds for your RC crawler
Compare two different gear configurations side-by-side
Many thanks to Travis Miller(https://www.facebook.com/TravyM) who originally created this sheet. I've put a lot of time into updating it and I hope it works for everyone.
I also want to thank Mehmet Tuzel(https://www.facebook.com/tuzelm) for all his help in double checking my work and many suggestions on axles and transmissions to add to the list.
Some transmissions do not require a spur and have one built in. In these cases, there will be a description of the built in spur after the transmission name. You'll need to select this spur from the spur list to get correct calculations.
For AR44 based axles, the OD1 = 27/8 gearing and OD2 = 24/8 gearing available from Boom Racing and Team Ottsix Racing.
The numbers in () after the axle names represent the portal gear sizes. They are lots of options for Capra/AR45P axles and a couple for Vanquish portals.
You can manually override the Pinion, Spur, and Tire Size values. There are too many options to maintain a complete list.
Please let me know of any other axles and transmissions that can be added. I know there are more, but I couldn't find info on some.
Overdrive % numbers may not match what you are expecting as many suppliers/manufacturers do not calculate this value correctly. This sheet uses the Percent Difference Formula.
If your overdrive % is a negative number, your rear axle will be faster than the front. This is usually not the desired setup.
If you are running a straight axle in the front and a portal axle in the rear, you may choose to mount your transmission with OD to the rear. To enable this, just check the reverse box under the transmission drop-down.
If you have any questions, issues, or suggestions, please contact me at jeff@ydrRC.com