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I'm not in a super rush as I waiting for a package from AE to replace my incorrectly machined CV. I have my sidewinder 3 4600 kv combo here for my re-re worlds and I'm wondering where I should start pinion wise. The spur is the kit one and I'm running a 5200mah 50c 7.4 2c liPo.

I'm thinking a 20t pinion. I have a few so I can go up and down but it will be a 2-3 tooth jump either way. I have time to get another pinion if someone out here has a magic number. It will be just for bashing around but I'd like to run on the cooler side. If a spur/pinion would be the better option I'm open to that as well.

"When in doubt, throttle out. It may not help the situation but it will end the suspense"

I love this line..... It will be exciting either way whatever the outcome.


It may not be much help but there is no magic number, mainly trial and error. Do to the variables you can get it roughly in the ballpark and go from there.

For what it's worth I ran a 20t pinion and 84t spur gear giving a final drive ratio of 9.45 with a 6.5t motor (5340kv, 390w) Runs were limited to 5 minutes.

Best option to start would be to calculate the FDR based on the motor recommendation (81 ÷ "X" x 2.25). If there is no recommendation I would try maybe a 22t pinion with the 81t spur and go from there. Run for a few minutes at a time checking temperatures, keep going up a tooth untill the motor gets reasonably warm but not so hot that you can't comfortably hold it for 5 seconds.

Looks like a 4600kv motor is somewhere in the 8.5 - 10.5 range. In the worlds car manual, the recommended starting gearing for those motors would be in the 19-21 range with an 81 spur. I guess try it there and watch your temps.

Wow, the castle CM36 4600 motors recommend a low gear ratio according to their gearing chart, 14.137 to 18.85 FDR.

Taking the B4 gearing as a baseline;
87 ÷ 12 × 2.6 = 18.85
87 ÷ 16 × 2.6 = 14.137

I ran a 4600 for a very short time in my RC10, I believe I was 20/81 or 84. It was ridiculously ballistic and quickly moved the motor into my 4wd and was much happier. This was almost 10 years ago now

I'm running a 21/81 and it flies. I liked it so much I went up to a 5700 and it's just stupid fast. I've got a 7700 in my B44 now

Didn't get my package and didn't work too much on on car this weekend. Something about the sun being out for the first time in a week.

I have the electrics done and mounted, just have to get bored tonight and set all the trims and such. I have the 19t on it now but have some smaller ones ready to go in case it gets too toasty.

I learned that about throttle back when I was a kid on 3 wheelers and it holds true now driving racecars. Though it's a good idea to lift when things start spinning.

AE is sneaky. I gave them my home shipping address for the replacement CV. I expected it to come to the house but nope, it just showed up at work today. Guess they looked up my email since I used my work one to make contact and got the shipping from there.

Little weird but whatever, it took them less time to get the replacement part to me than it took to ship the kit from Cali via donkey.