What motor has the least over speed resistance?

[A22]

I've been riding a couple of bikes with the Bosch CX motor and once I get over 32km they feel like hitting a wall. I've briefly ridden the Giant (Trance & Reign 2023 models), Shimano EP6 and 8 (not EP801) motors and don't recall as much resistance over the speed assistance limit but then I didn't get much chance to push those motors.

So I'll be buying a emtb in a month (all saving going to plan) and would like to know which system has the least resistance once over the regulated assisted speed limit, any insight would be appreciated.

I already appreciate a big part of the resistance is tyre choice.

 

[RebornRider]

Just make sure the power is off, lift the back wheel off the ground, and run the pedal with your hand. That is the resistance you'll have from the crank shaft seals and the clutch. Unless the design is pure rubbish, you are not spinning the motor when the assistance drops to zero..

Actually, resistance at 32 kph will be higher than hand pedaling because crank shaft seal and clutch resistance go up with high rpm.

That wall you're hitting is the difference between your legs putting in maybe 300 Watts when the motor is assisting at 31 kph, and 700 Watts when the assistance goes away at 33 kph.

FWIW, it is very easy to run the pedals of my Specialized Turbo Levo when the bike is on the stand. I think it takes more power to overcome the flywheel effect of the rear tire than to push through crank resistance.

 

[A22]

I think your point about going from 300W to 700W leg input makes complete sense especially when combined with the fatter grippy tyres on the Trek Rail I’ve been riding. Wind + Tyre resistance at 32kph I think would be more than the motor resistance.

I won’t get so hung up on this as a bike choice now thanks.

 

[RoJo]

I think your point about going from 300W to 700W leg input makes complete sense especially when combined with the fatter grippy tyres on the Trek Rail I’ve been riding. Wind + Tyre resistance at 32kph I think would be more than the motor resistance.

I won’t get so hung up on this as a bike choice now thanks.

I agree that testing with motor off is the only way, because a more powerful motor with a more abrupt cut off is going to feel like more resistance after the limiter but this may not be the case, it was just helping you more before the cutoff.

I think resistance is low on all major motor brands, my friend did timed loops eBike motor off Vs manual and the times are remarkably similar when you consider the weight difference, meaning resistance is not a big player.

Personally I would prioritise motor efficiency (which can allow you to run smaller lighter battery), reliability, serviceability and weight, and I think Bosch is the clear winner here.