[RC-Monster Mike]

Zenoah makes gas motors - not electric. Many/most 1/5 conversions that make use of the clutch may use 10mm shafts to be compatible, but that is an adaptation rather than an established standard imo. Where do you get a 10mm bore pinion or a selection of them? I know I chose 8mm for my pinions based on a couple reasons - 1st, I prefer Neu motors and the 22 series is a nice choice for 1/5 scale - these motors happen to be available with an 8mm shaft(not 10mm). Secondly, a 10mm shaft would inherently limit the the tooth count on the low side, which forces a higher rollout - works on a gas powered Zenoah, but in sensorless brushless, to much rollout leads to cogging at startup along with excessive heat - 8mm allows plenty of shaft strength and magnet adherence, while also allowing reasonably small tooth counts to be used for greater reduction. These to reasons along make 8mm shafts make sense in my eyes. Again, it is also easier to make a sleave for smaller bore pinions than it is to bore out each pinions used, so it makes sense from this standpoint as well.