Pondering on motor power ...

[danfoto]

This is in the context of an old git riding crank-engined ebikes on the roads for everyday transport. 1500 miles a year in all weather except ice, can't be doing with Magic Hats, etc etc ...

So, the last ebike had a 70N/m Yamaha motor and 8-speed Nexus hub. Brilliant bike, but it also had a crossbar and in due course that posed problems due to medical issues. Current bike of identical type but different make has a 65N/m Shimano motor and Enviolo hub, and compared to the previous bike this one couldn't pull the skin off a rice pudding - which has got me wondering. Is just an 8% or so reduction in torque going to be really noticeable in normal use? Or is the very significant difference between these two bikes more likely to be down to that 8% or so plus perhaps losses from the Enviolo hub?

Best example I can give to illustrate the point is a mile-long hill nearby which on the previous bike I consistently did at never less than 12mph on power level 4 of 5. On the present bike the best I can manage is 9mph pedalling like a mad thing on full power in a relatively low gear, and by the time I get to the top I'm knackered! And I definitely haven't lost any strength or endurance.

Anybody care to share their thoughts?

 

[soundwave]

i went from a bosch performance motor with 63nm to a cx motor with 75nm and did not think id feel the difference but you can and the cx has way more kick when you start to peddle.

 

[danfoto]

i went from a bosch performance motor with 63nm to a cx motor with 75nm and did not think id feel the difference but you can and the cx has way more kick when you start to peddle.

Yes, but that's a 20% increase and I'd expect to notice such a significant difference.

 

[soundwave]

thing is when manufactures say what nm the motor is there not done in the same way but the Yamaha motor is very good for power and not so much with shimano.

so unless you ride them both to feel the difference you cant really tell bar reading revies of each orf the motors.

 

[danfoto]

Any idea how a 2023-spec Bosch rated 75Nm is likely to compare to the 2019/20-model 70Nm Yamaha PW series

 

[flecc]

The Enviolo hub gear can't compare with the Nexus 8 for efficiency and I'd say that is a major factor. Add the power difference between the two motors and combined there's the over 25% difference in experienced climb performance, leading to your exhaustion.

Swapping out the Enviolo for a Nexus 8 would help, but I fear you'd still be unhappy with the Shimano motor performance after the excellent Yamaha.
.

 

[matthewslack]

Hard to know the cause without more numbers, which might not be available easily.

I'd expect the enviolo to be more lossy than a hub gear, but not hugely. Add lets say 5% to the 8% lower torque and that's 13% or so less help, which would be noticeable. If the percentage assistance each motor is giving was also lower for the Shimano then the total difference might well be as big as you describe.

But without the numbers no way to know for sure.

 

[soundwave]

well the new gen 4 smart motors are now 85nm so you will feel that.

Performance Line CX: the sportiest Bosch motor for eMTBs

The best eMountainbike experiences: a powerful drive with unique dynamics and the best possible traction on trails thanks to the 85-Nm Performance Line CX.

www.bosch-ebike.com

 

[sjpt]

There's probably a bigger difference than 8% in the ways different manufactures measure and publish the torque.

 

[Michael Price]

Is there a web site that shows the torque

preferably based on independent measurement but I think that is asking too much!

 

[Sturmey]

I dont have direct experience of Shimano but sometimes bike with torque sensors don't reach full power if the sensor is not properly calibrated (or the rider has weak legs.)

W013 – Initialization of torque sensor not completed successfully
Restrictions: Power assist may be lower than usual.
Remedy: With foot off the pedal, press battery power button and turn on power again. If no improvement, contact place of purchase.

Just ride

It’s time to just ride. Shimano will help you get there.

www.shimano-steps.com

 

[AntonyC]

Add to all the above that you're probably experiencing two quite different "250W" power curves under conditions (cadence, sensor response) where they don't give maximum torque. And thankfully there are different ways to qualify as 250W, or they might all feel like your Shimano. Have a play with https://ebikes.ca/tools/simulator.html

 

[georgehenry]

When I bought my Haibike Yamaha hard tail in 2015 the owner of the business steered me towards the Bosch powered Haibike hard tail, by saying that the Yamaha motor was new to Haibike that year and little was known about it in comparison to the Bosch motor.

In fairness to him, his shop had run a free well run try out day in The Surrey Hills that had allowed me to ride the two systems back to back against each other on hilly single tracks with roots and stones and mud, and I simply preferred the Yamaha motor.

I got a hundred pounds off for attending the test day if I bought a bike afterwards. The Haibike Yamaha hard tail bike in 2015 retailed at £1,850, so I bought mine for £1,750.

This seemed a good price to me. I owned a generic Chinese cadence controlled geared rear hub motor bike, an Oxygen Emate, that I loved and had paid £1,399 for in 2011 using a ride to work scheme. A £350 difference for the more sophisticated torque controlled crank drive bike seemed pretty good. It had the important minimum of components I needed for off road, hydraulic brakes and an adjustable air shock fork. If I had been swayed to buy the Bosch powered hard tail Haibike it would have cost me just over £2,500 from memory, so it was a good job I preferred the Yamaha.

The Emate had in a strange way enabled the purchase after I was knocked of it by an Audi and received a personal injury claim pay out.

Incidentally in 2015 the bosch motor was stated to have 55nm of torque and the Yamaha 60nm of torque, so on paper the Yamaha was both cheaper and more powerful. Although riding the bikes to see how they feel is a much better test than poring over the specifications.

Without really knowing why I instinctively preferred the full size chain ring of the Yamaha in comparison to the small drive cog of the Bosch at that time. It allowed you the possibility of a twin chain ring system, though I never have, and the ability to buy any chain ring you fancied of the right BCD. Though I did not know it when I bought the bike it also meant that there was no drag from the Yamaha motor when ridden without assistance, when the small cog Bosch motor of that time added quite a bit of drag. I appreciate that a lot now as I often ride the bike with no assistance.

The Yamaha motor reminded me of a Yamaha DT175mx motorbike I owned, producing a lovely bulge of power right from the beginning. They called it zero cadence, but it felt like instant oomph. Some criticized it for the power petering out too soon, but after riding dirt bikes I thought the power was just where you most needed it off road. Some said people who like to spin at higher cadences preferred the Bosch. That's why test riding different systems is important.

Not everything in the garden was rosy. The raw power of the Yamaha without the interrupt technology when gear changing of the Bosch could mean wearing out drive train components very quickly if you were careless.

However I quickly developed my riding style to mitigate the power when changing gear.

Oh and The Yamaha motor has turned out to be infinitely tougher and more reliable than The Bosch. though both have the infuriating defeat technology that has meant I have not bought a replacement.

What does all this waffle mean. Chop in your weedy shimano and get another Yamaha powered bike, or at least test ride a few before buying your next bike. Life is too short to be riding an unsuitable bike!

 

[Bonzo Banana]

I guess two other variables are the gearing itself and its ratio plus for how long peak torque is maintained, could be 5 seconds, 50 seconds or 50 minutes. Without stating how long peak torque is maintained its hard to compare. Maybe allowed rider cadence is also a factor, if you ride beyond the motor's allowed cadence and the motor switches off that could negatively impact power. Mid-drives lose some amount of power through the drivetrain probably around 2Nm give or take a bit.

If a mid-drive motor has 65Nm peak torque at the crank that is about 63Nm allowing for losses in the drivetrain if the gearing is 1:1 i.e. 32T at the front and 32T at the rear but lets say you had 48T at the front and 32T in the ear you are down to 42Nm max torque.