Red Mini

Ok, first time here and looking for some guidance.

I just upgraded to a TOP Racing Photon and looking to race it at Castle Hill. I have no idea what spur/pinion gearing to run on it. Looking to run a Johnson 540 motor.

Any ideas would be appreciated.

Odd

One of the most common things that I gear for is motor heat which depends on number of things:

1: Vehicle Weight
2: Battery Voltage
3: Type of Track (Fast/Slow,Long/Short)
4: ESC

I try to gear to go as fast as possible with the best accelleration and top speed for the track while not going over 150F degrees.

truman33

how do i best ask this question? im experimenting with gear ratios and was wondering if there is any difference with spur size when picking a final gear ratio? For example: a 76/26 combo and a 78/27 have just about the same ratio, but is there a difference with one spur being bigger than the other? thanks to any help.

Odd

Absolutely there is.

Smaller ratio = more top speed, less torque, more motor heat

Bigger ratio = less top speed, more torque, less motor heat, but you'll chew up gears frequently.

Small changes in the diameter of the spur and/or pinion can have a huge impact on performance, even if the difference is just 1 or 2 teeth.

Pinions give much greater jumps in performance, while spurs are more for fine-tuning the ratio.

A good target for finding gear ratio is to keep in mind that you want to be able to:

-Hit top speed on the longest straight before the braking zone.
-Have enough torque to comfortably clear the jump with the shortest launch line (like out of a corner, and then immediately into a jump, etc.)
-A solid 5 minute run with motor/esc temps below 150F
-A reliable ratio that won't chew up gears.

At the end of the day though, different driving styles will determine what ratio is best for you. Best advise I can give is to get some pinions and a temp gauge and start experimenting. Once you find a pinion you like, dial in the ratio with spurs.

Dave H

Assuming the same ratio, perhaps use 78/26 and 81/27 for a more exact comparison just for discussion purposes, the difference will typically just be motor position. Which can change vehicle handling some due to the different weight position and balance.

The spur can be used for fine tuning gearing, but is also used to achieve a different range of gearing, due to motor adjustment limits.

Significant change in gear wear typically is only an issue with much smaller pinions. Hard to give an exact number, but perhaps 12-14 teeth and below, the tooth engagement won’t be a smooth and will result in some more wear. Assuming proper gear mesh normally not much of an issue.