speedmd wrote:Motor torque certainly loads the motor bearings. What else transfers the drive force the motor generates? It is only connected to the frame through the bearings.
I suppose there is some truth to this, in that the forwards motor thrust on the bike from the motor is coupled through via the bearings. But thrust forces are just a fraction of the downwards load forces from mass vehicle mass, and much less even than the load forces from a pedal chain, as a pedal chain tension is like 5-10 times higher than the vehicle thrust it produces. So ultimately it's fair to say as Chalo did that motor torque doesn't in any noticeably way increase the loads that the bearing sees.
Anyways the reason that I'm piping in here is because we run into this misperception at our shop all the time, with people thinking that they notice extra drag in their hub motor and assuming that this must be the result of a shot ball bearing. But even if you DO have a shot ball bearing, the extra resistance that it causes doesn't even remotely register when compared to the cogging drag, tire rolling resistance, or anything else impeding the movement of the vehicle, and to think that you could actually see a difference in your measured power consumption with a new vs. damaged ball bearing even with precision instrumentation is extremely unlikely.
That said, we've seen lots of worn out ball bearings in need of replacement, and water/corrosion damage is one of the prime reasons for that, (poor hub machining tolerances resulting in too tight / too loose a fit is another). Most hub motors now have decent rubber shaft seals on them to keep the bearings protected from the elements, but not all of them. If other materials like Ceramic would intrinsically hold up better with environmental exposure, then that could have some merit and justify the extra price.
So to repeat what others on this thread have stated, there can be valid reasons for changing your motor ball bearings, but reducing wheel drag / increasing motor efficiency is not one of them.
Previously competed in the Suntrip race on a back to back tandem solar powered row/cycle trike
. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.
Now back in Vancouver learning to be a dad with my Big Dummy Frame (yes This One
, thanks ES!) with GMAC 10T rear hub motor, Phaserunner controller, and 52V 19Ah EM3EV pack
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