R/C Tech Forums - View Single Post - Spur to Pinion ratio for Reedy S-Plus Spec competition motor
Old 07-04-2019, 06:59 AM
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Originally Posted by JBMotorsports29 View Post
What is the best spur to pinion gear ratio to get the best top speed out of a Reedy 17.5 S-Plus Spec competition Motor? I race on road touring and I'm looking to get max speed out of that motor since I'm currently running a heavier chassis than the competition.
This question has been asked so many times before and there is no magic answer, period. If you are racing, you must use Final Drive Ratio (FDR) to obtain optimum settings and there are multiple other variables to consider. Are you running indoors or out, on carpet or asphalt, with rubber or foam tires, what chassis are you running, what motor timing are you using, what ESC boost (or perhaps blinky mode), etc....?

When I run a 4wd sedan indoors on a carpet track with Sorex 28R rubber tires I like to start with an FDR around 3.8 and after a few runs adjust up/down from there. The 17.5 class has used blinky ESC settings for some time now so there is no software boost/turbo on the speedo, but you can still play with motor timing. I am not familiar with that Reedy motor but it sounds like it might have fixed timing which means one less thing to fiddle with.

This should leave you with only spur and pinion to change to obtain a favourable FDR. I prefer 64 pitch gearing indoors as the adjustments are finer and I can dial in my car better. 48 pitch still works though so don't worry.

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