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My current project is an Optima Mid that's going to be setup as a mid-motor RWD. It has the ball diff gear innards of a Turbo Optima Mid SE, I'll be upgrading the balls to ceramic and will polish the diff plates to smooth (wet-sanding with 1500-grit).

The stock spur gear & slipper on this car has been upgraded to a 48-pitch fine-tooth Robinson Racing gear. I received in this parts lot a series of RR gears, from 75T to 93T I believe, and one pinion gear to match that's a 14T. I believe the previous owner had it setup with the JG Racing truck conversion.

I also received a bunch of stickers showing all the various pinion/spur gear ratios but I'm not sure which spur gear I should start with; a smaller or bigger one? I'm installing a 12T brushless motor & ESC combo from Toro.

http://www.ebay.ca/itm/SKYRC-toro-leopard-12T-2p-Brushless-Motor-3300kv-60A-V2-ESC-RC-car-truck-buggy-/290825206167?pt=US_Character_Radio_Control_Toys&hash=item43b6887997

That all being said, I'm intending to run it as a RWD-only and would like some suggestions for a starting point for a final gear ratio...what combo of pinion & spur should I start with?

Thanks to all the crickets for answering...how about some Optima Mid enthusiasts?

EDIT: Looks like I have a starting point, anyway...the very last post in this topic on Oople suggests an 18T pinion & 81T spur gear. Thanks crickets!

http://www.oople.com/forums/showthread.php?t=4888

I would start with an 18T pinion & 81T spur gear...

Todd

p.s. it actually is what my optima mid is at but I have no real idea

what is the internal ratio? The 18/81 is a good start if the internal ratio is around 2:1 or so. Really, with a brushed motor you are gearing for run time and motor temps, so you will have to adjust from there.

according to a twister motor sheet, the optima mid is a 2.64:1.

whoops...the 12t thing confused me, I thought you were running brushed. 12t isn't a 'common' brushless wind.


so you are concerned with motor temps. with that internal ratio, the 81/18 is probably fine, but you may find you will be going up a bit on the pinion. Better to work your way up to motor temps than to smoke it being overgeared.

jwscab wrote:what is the internal ratio? The 18/81 is a good start if the internal ratio is around 2:1 or so. Really, with a brushed motor you are gearing for run time and motor temps, so you will have to adjust from there.

What scr8p said. He must have some Kyoshos stashed somewhere...

Thanks gents, I'll see what spur gears I have, I have a good selection to choose from...48p pinion gears, not so much.

Coelacanth wrote:What scr8p said. He must have some Kyoshos stashed somewhere...

you know its true

Todd