RCU Forums - View Single Post - Brushless car vs. boat motors - make me smart!
Old 05-08-2021, 04:54 PM
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You should select the KV rating for the type of driving you're doing, that's after you've chosen the size of motor you need based on the vehicle you're driving. 1/10 scale motors are 36mm diameter cans, 1/8 scale are 40mm, 1/5 scale I believe are in the mid to upper 50mm range; I believe 57mm?

So, if you're going to race a 1/10 2wd short course truck then you're looking at a 36x50 or 36x60mm can. These are pretty standard so anything on the market intended for 1/10 scale vehicles will be those dimensions. If you were running a 4wd 1/10 then it would be a "short course" motor which is the same diameter at 36mm but they're around 65-70mm long.

Honestly, you don't need to get that technical about it unless you're trying to custom build a specific vehicle for another purpose; like a dedicated speed run machine or something else extreme. Based on the vehicle you intend to use you would search for a brushless system that is intended for a vehicle that size. Also, sensored systems are much preferred in racing versus unsensored motors. In organized racing the club may have certain requirements regarding the type of motor system they will allow you to run. Check for any of those rules at your track. If it's just buddies having fun then I guess anything goes.

Back to KV ratings, it also depends on the vehicle and track conditions. For most 2wd racing I would suggest no higher than 3500KV. You generally see low 2000s up to low 3000s on the tracks running 2S LiPo batteries. 4wd SC motors can start in the mid 2000s and run up to 4000 or so KV, again on 2S. Going above 4000s in racing environments is not advisable and again, tracks may have rules in place too. The 5000+KV systems you see available are best suited for open spaces and bashing. You wouldn't fare well on a track with such a high RPM motor unless your track has long stretches and big sweeping turns.