Featured Torque curves - Shimano, Bosch, Brose, Yamaha

100 Cols

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#1
This is not Shimano related post, but couldn't find a better place for posting, so here we go.

I found power curves of few motors from the electricbikereview.com and did some "reverse engineering" to visualize also the torque curves (something I've not seen before). I was interested in torque, because when climbing, torque is usually more relevant than max power and also because I was frustrated of reading manufacturer torque claims without any reference to corresponding crank rpm.

Some of you might be interested in this, too:

torque-reverse-engineered-png.1352


The original power chart looks like this:
powers-jpg.1356


Flame on.
 

Rob Hancill

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#2
Interesting. I wonder how accurate that source data is though?
 

ccrdave

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#3
is that specialised brose or another brand? in my experience the brose motor in other brands performs very different from the specialised tune
 

Kernow

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#4
Interesting but I don’t understand the high torque at low rpm ,on the top graph , my shimano feels dead below 60 rpm as it should I think
the power diagram describes how the motors I’ve tried felt to my legs , but they all feel so different depending on which setting is used , and surely the curve for the trail or middle adaptive modes is going to be way different to the full boost setting , ?
I think that unless you have spent a little time working on your cadence it’s all a lot more difficult to understand ,
 

100 Cols

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#5
Source data was probably "leaked" from Bosch without any reference to the measurement method, so accuracy is pretty much unknown. However, it seems that calculated torque (out of those power curves) actually corresponds pretty well to the claimed torque figures (with the exception of Brose):

- Bosch Performance Line: 63 Nm claimed, vs. 63.5 Nm @35 rpm calculated
- Bosch CX: 75 Nm claimed, vs. 74.6 Nm @45 rpm calculated
- Shimano E8000: 70 Nm claimed, vs. 69.5 Nm @35 rpm calculated
- Brose: 90 Nm claimed, vs. 74.2 Nm @20 rpm calculated
- Yamaha: 70 Nm claimed, vs. 70.1Nm @25 rpm calculated

I should have said in the previous post that the torque charts above are "polynomially smoothed"
 

Rob Hancill

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#6
I bet that Brose was the old 1.2 motor as the source info was posted in July 17 (and likely tested much earlier than that). That would have been before the Brose 1.3 motor was released.
 

100 Cols

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#7
Interesting but I don’t understand the high torque at low rpm ,on the top graph , my shimano feels dead below 60 rpm as it should I think
AFAIK, that's how electric motors generally behave, their torque goes down when they approach their max angular speed. Also, power and torque are directly related, if you know power and angular velocity (rpm), you can calculate the torque. And vice versa.

surely the curve for the trail or middle adaptive modes is going to be way different to the full boost setting , ?
Yes, of course.

I think that unless you have spent a little time working on your cadence it’s all a lot more difficult to understand ,
I'm afraid I don't understand this. I have spent _years_ working on my cadence.
 

Kernow

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#8
I'm afraid I don't understand this. I have spent _years_ working on my cadence.
Sorry I didn’t make that comment very clear What I mean is unless a rider knows ie has counted / checked cadence somehow it’s harder to get a feel of what the graph means , if you know your cadence averages say 80 rpm it’s easier to read the info and see where each motor will work best for a person
It’s a good interesting thread
 

Gary

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#9
I have spent _years_ working on my cadence.
What do you mean by "working" on it?
It takes very little time to train your body to reach higher peak max cadences. and not very long at all to raise your sustainable (comfortable) high end cadence.
Mine are both well above average from nothing more than boredom and having a Garmin Cadence sensor fitted to my roadbike
 

100 Cols

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#10
What do you mean by "working" on it?
It takes very little time to train your body to reach higher peak max cadences. and not very long at all to raise your sustainable (comfortable) high end cadence.
Wow! I'm amazed that you think you know my body or how long it took me to re-learn to pedal at high cadences. That's quite a big headed claim there.

With working on it, I mean that after two strokes I've had (2007, 2014), I've had to re-learn walking, coordination, keeping balance and finally cycling and then higher cadences. It took more than "very little time", actually it has taken years, no matter what you claim.

Mine are both well above average from nothing more than boredom and having a Garmin Cadence sensor fitted to my roadbike
Cool. You're the man.
 

Gary

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#11
Sorry man. I misunderstood what you were saying completely :oops:

all I meant was improving rpm is much more to do with practice and honing a smooth pedalling action than "working" harder.
 

Kernow

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#13
Never had cadence reading on a mtb before , off road up and down humps and bumps combined with the ebikes power assistance make it harder to stay in a good range , it’s much easier to suddenly get too fast or slow down when your not working too hard An above average cadence really works against you with the motors limit
 

Kernow

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#14
since owning my Emtb one thing I've struggled to work out is exactly how cadence effects asistance with my Shimano motor betwen the various modes. Although I will say since the update I did a couple of days ago it all feels markedly more intuitive and far more useful than it was stock.
It takes a while to get the hang of it for sure , and that initial puppy dog reaction to go everywhere in boost doesn’t help . I found using trail and riding up short but steep climbs is a good way to get used to it .
 

Japuserid

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#15
What a brilliant bit of work and looking at the torque graph especially I really think it's not far from the mark at all. I had the CX for 2 years, undoubtedly the strongest of the bunch, Been riding the E8000 for a couple of months, was initially a little disappointing compared to the CX but only a little and now beginning to love it's more subtle nature. Limited experience of the Yamaha but swapped with a mate for an hour, strong at the bottom but run's out of puff a bit too early and the Levo I tried with the old Brose 1.2 was just, sorry to say very weak. The original source material was dated July 2017 so would be very interested to see how the newer 1.3 Brose compares? Very much improved by all accounts, but as the graph show's it would need to be.
 

kcarbon

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#16
From experience with Dyno's & riding & racing motor bikes. the only chart we need to look at is the Torque curve, as with MC's that is all I really feel, the power I can't really feel that it mostly shows up in higher speed ( I can feel the speed!! but the torque is what you feel being thrust forward )
all over I am very happy with the bike I have, it does everything I ask, and if I want more,.... I just peddle harder.
cheers , interesting thread
 
May 14, 2018
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#17
Great analysis. I've ridden all but the Shimano and couldn't "feel" the differences as well as some have articulated; guess I'm too stoic. However, this explains why my SDURO signs off the way it does.
 



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