lol thanks for the link, but I dont even know half of that info to properly fill out that chart.

I think since I plan to run 1/8 buggy tires a good bit of the time (being 4inches +) I will try a 12 tooth pinion to start with. Then if its geared plenty low with smaller tires i will jump up to a 14/15 later once I get a few runs in.

even with a 12 tooth on 3s think I will still be above 30 with stock tires? road rage 2.2's?

Differential Ratio: 3.25
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 47
Pinion Tooth Count: 14
Total Voltage: 11.1
Motor KV: 3500
Tire Diameter (inches): 3.5
Tire Ballooning (inches): 0.3
Motor Current Draw: 0
Motor coil Ω: 0
Spur/Pinion Ratio: 3.36 : 1
Total Ratio: 10.91071 : 1
Tire Circumference (inches): 12.88 inches (327.17 mm)
Total Motor Speed: 38850 RPM
Vehicle Speed: 43.43 mph (69.77 km/h)
Estimated Adjusted Speed: 41 mph (66 km/h) - 6% loss
Effective KV Value: 3500
KT constant: 0.39 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...


The first couple fields you can use the presets, crt.5 diffs, center diff direct drive for tranny, stock is a 47t spur

14t pinion on stock tires will give you about 40-41MPH depending on ballooning of the tires it may be more

Sweet, thanks for the help! 40-41 on a 14 tooth? Damn those stock tires are pretty short too (cant be more than 3 inches?)

I just looked at the field for circumference and you put in 12.88. I converted that and it comes out to be 4.1 inches. Stock tires are pretty tiny right? More like 2.8- 3 inches tall? I tried checking tower but they only have the width for the stockers.

I would like 40mph to be the top speed (45 is fine as long as im not getting serious heat). Maybe I should swing for the 12 tooth pinion so im safe for the bigger tires?

stock tires are about 3.5" tall and I put in a ballooning radius of 0.3" so that does equal 4.1". However at those speeds the ballooning may be greater than 0.3" which will increase your speed even more. IMO I'm not sure that your going to be able to gear a 3500kv motor down enough runnin 3s to run any bigger of a tire than stock. A 12-13t will prolly net you 40MPH with the ballooning you'll have at that speed. To figure in bigger tires your pinion is going to have to be crazy small unless those bigger tires don't balloon as much. I know that my slash tires don't balloon as much but geared for about 38MPH they still balloon about 0.25" on the radius. IMHO to run 3s I'd pick a little slower of a motor. Personally I think I'll be staying with 2s on my crt.5, my Medusa motor runs plenty cool, much cooler than my vxl did in my rustler, that thing got HOT!

wow stock tires are much taller than i would have guessed! I guess going from a 3.5 tall tire to a 4.0 - 4.5 will not be too drastic of an increase. The 1/8 tires do not balloon that much as the sidewall is so thin so that should help.