# What is the drag level of the various motor systems?



## Francis Cebedo (Aug 1, 1996)

I did some quick research but could not find the answer. What is the amount of drag that the various motor systems introduce to the drivetrain when the motor is off?

Surely, some euro scientists would have measured by now.

As far as I know,

Shimano - almost none since clutch disengages motor
Yamaha - none since clutch too?
Bosch - a lot since draggy and tiny chainring
Brose - quite a bit.
Fazua - none since on a one way gear?

I don't know, is it 2 watts or 20 watts. It seems to be noticeable not only when the motor is turned off but when assist shuts off at 20mph. Very hard to pedal at 21 or 22mph.


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## Francis Cebedo (Aug 1, 1996)

craigsj said:


> I think this is a good question. I'd also suspect that a good, published test would cause these problems to get fixed pretty quick!
> 
> I'd say the answer is that power loss is going to be a percentage of total power for the draggy systems. Bosch, for example, has to step up the rider cadence to match the small ring. If the motor is driven by the crank, then losses increase with speed. Won't be fixed amount, much worse than that.


Yup, hopefully we can find the data soon.

It's basically like having a frozen bottom bracket on some of these systems. I bet we couldn't turn that spindle by hand if there was not crank attached.


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## hikerdave (Mar 8, 2006)

fc said:


> I did some quick research but could not find the answer. What is the amount of drag that the various motor systems introduce to the drivetrain when the motor is off?
> 
> Surely, some euro scientists would have measured by now.
> 
> ...


On my Yamaha PW-SE the motor spins when power is off. It feels like there's a lot of inertia in the system - once it gets going the drag feel like the difference between a sticky downhill tire and your average knobby tire.

Another motor attribute I'd like to know is how quickly the freewheel engages; Yamaha PW-SE is sloppy with 18 points of engagement leading to a lot of pedal strikes because the combination of that and the hub makes pedal engagement over rocks unpredictable. Yamaha PW-X improves that to 24. I'd like a bike motor to have a sprag or roller clutch more than I care about motor disengagement at speed.


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## Francis Cebedo (Aug 1, 1996)

Worth noting that the cost of a low-drag, motor system is a clutch that kicks you. The Shimano goes on/off, on/off and it's part of the riding experience. It's not the motor that's doing that but the clutch.

It didn't really bother me too much but on Boost mode, it sucks. It's noticeable and it causes you to lose traction ad key moments. They should not have programmed it that way.

Now that I'm riding the Levo 2.0, you can see how much of a smoother system it is. It just goes on and off and you can't even tell. But there is drag, a bit of it.


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## akaktm (Sep 15, 2008)

The new Brose on the specialized has no more drag on coasting than the E8000 Shimano from what I can tell. In fact, on coasting, it seems to have no drag.


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## Francis Cebedo (Aug 1, 1996)

akaktm said:


> The new Brose on the specialized has no more drag on coasting than the E8000 Shimano from what I can tell. In fact, on coasting, it seems to have no drag.


On the bike stand, turning the pedals 1mph, it feels like a half-frozen bottom bracket. Really feels significant to me.


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## levity (Oct 31, 2011)

fc said:


> ... Now that I'm riding the Levo 2.0, you can see how much of a smoother system it is. It just goes on and off and you can't even tell. But there is drag, a bit of it.


Curious as to how you feel drag with the Levo's Brose motor. Do you have a way of measuring it? With the chain off the front ring the cranks don't spin quite as freely as a regular bike with good bearings, but I can spin them with one finger almost effortlessly and they continue spinning for 2-3 revolutions. The tiny amount of "drag" just doesn't seem significant.

In addition, the Brose motor uses a sprag clutch which is fast engaging and disengaging and offers low resistance when disengaged. The cranks spin freely backwards. Onyx hubs, known for instant engagement and little drag, also use a sprag type clutch.


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## hikerdave (Mar 8, 2006)

levity said:


> Curious as to how you feel drag with the Levo's Brose motor. Do you have a way of measuring it? With the chain off the front ring the cranks don't spin quite as freely as a regular bike with good bearings, but I can spin them with one finger almost effortlessly and they continue spinning for 2-3 revolutions. The tiny amount of "drag" just doesn't seem significant.
> 
> In addition, the Brose motor uses a sprag clutch which is fast engaging and disengaging and offers low resistance when disengaged. The cranks spin freely backwards. Onyx hubs, known for instant engagement and little drag, also use a sprag type clutch.


That sprag clutch must be nice. On my Yamaha PW-SE the combination of motor and freewheel ratchets makes the engagement angle pretty unpredictable which means more pedal strikes; I miss my old Hadley hub with 72 POE.


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## Bigwheel (Jan 12, 2004)

On my POS TSDZ2 kit steel hardtail bike I can pedal all day long on flat ground and not notice any drag at the cranks. But encounter any type of grade and it feels like the brakes coming on incrementally so I attribute most of the drag problem to the fact I am on a 45lb bike. 

Any type of gear reduction system, unless it is clutched out of the equation, will exhibit some drag, that is why the Pinion type gear boxes and IGH systems are not more favorable along with complexity, reliability and weight considerations. 

My DD hub bikes which are notorious for drag due to the magnets interacting with the stator at all times both running Statorade do not exhibit the drag coefficient that they do without it plus it also helps them run cooler. I did a 5 mile hill climb to a hot springs in the Olympics once and left the battery at the car cause I was riding with a friend that had a push bike and never really noticed it was there. But put the battery weight on and it will exhibit the same type of elevation induced weight drag as my mid drive.


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## Francis Cebedo (Aug 1, 1996)

levity said:


> Curious as to how you feel drag with the Levo's Brose motor. Do you have a way of measuring it? With the chain off the front ring the cranks don't spin quite as freely as a regular bike with good bearings, but I can spin them with one finger almost effortlessly and they continue spinning for 2-3 revolutions. The tiny amount of "drag" just doesn't seem significant.
> 
> In addition, the Brose motor uses a sprag clutch which is fast engaging and disengaging and offers low resistance when disengaged. The cranks spin freely backwards. Onyx hubs, known for instant engagement and little drag, also use a sprag type clutch.


I can measure tomorrow. I can pull it from the crank arm hole with a fish scale.


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## richj8990 (Apr 4, 2017)

If it matters to anyone a (Bafang) hub drive really, really has a lot of drag. I know this because my pedal assist broke and I've been having to throttle for the last week. I pedal w/o electric power down slight grades and boy is it harder when it gets level. I've ridden several 45-50 lb normal bikes in the past, and this is way, way worse than those. I'd say with no electric power it's almost impossible to do more than a 5% grade w/o the granny gear.


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## Francis Cebedo (Aug 1, 1996)

Ok I've got some numbers. I have to videotape it to better illustrate. So there's no numbers out there that are more scientific huh.


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## akaktm (Sep 15, 2008)

Administrator, depends on whethe we are speaking about pedaling or coasting. There is no rear wheel drag on coasting. Complete free wheel. Once broken in pedaling resistance is only slightly more than a standard bike. It’s there but minimal.


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## Francis Cebedo (Aug 1, 1996)

Administrator? 

Pedaling of course... with the motor off


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## .WestCoastHucker. (Jan 14, 2004)

i have a Brose class 3. i don't notice a lot of drag when the motor is off, but when it's on, i do find it harder to push faster than pedal assist allows...


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## 33red (Jan 5, 2016)

.WestCoastHucker. said:


> i have a Brose class 3. i don't notice a lot of drag when the motor is off, but when it's on, i do find it harder to push faster than pedal assist allows...


My Yamaha 2017 kind of feels that way. I am still kind of new and learning but my general impression is Yamaha and Shimano 8000 are really user friendly in the sense that it is a gentle support if we do not pay attention to the noise it feels natural. When the max assist is selected the animal becomes a bit wild and it seems to be the same for the 4 major motor manufacturer. They like to brag about over 250% assist because some want that, a bit of a motor bike less restricted. Sometimes i forget to start my assist so the drag is not bad but occasionally i feel it is slowing me. With 4 sensors it is working well but there is still some place for improvement to eliminate some jerking.
In 2 years the noise will be eliminated so new bikes will be needed.
In an other 2 years no more jerking so new bikes will be needed.
Here we are stuck, they are new so there are none used available except for 499$ crap. A bit like 4 years ago no used fat was available.


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## portnuefpeddler (Jun 14, 2016)

My Bafang BBSO2 has very little drag, so little I rode two blocks today (flat, paved) before I realized I had left the battery in my crane. I have a storage compartment just for the ebike in my 30 ton rig, it's super handy for using as a dingy. My BBSHD fatbike, in general has a lot of drag, I don't forget the battery, ever, not yet anyway, with that beast.


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## levity (Oct 31, 2011)

fc said:


> Ok I've got some numbers. I have to videotape it to better illustrate...


So what did you find out, fc?

I made a crude measurement on my '19 Levo. With the chain off the cranks spin forward 2-3 revolutions with a light flip the pedal. I put some small weights on the pedal and found that it took about 100-110g to cause it to drop. The crank arms are 165mm, so that corresponds to roughly 1/8 ft. lb. (<0.2Nm) of force if my math is correct. Not much compared to what even I can push, and way less than other sources of drag like the tires.

Also much less than the Levo motor output, of course. Did your motor have similar, or more, "drag"? Enough to be significant if pedaling with the motor? off?


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## hikerdave (Mar 8, 2006)

levity said:


> So what did you find out, fc?
> 
> I made a crude measurement on my '19 Levo. With the chain off the cranks spin forward 2-3 revolutions with a light flip the pedal. I put some small weights on the pedal and found that it took about 100-110g to cause it to drop. The crank arms are 165mm, so that corresponds to roughly 1/8 ft. lb. (<0.2Nm) of force if my math is correct. Not much compared to what even I can push, and way less than other sources of drag like the tires.
> 
> Also much less than the Levo motor output, of course. Did your motor have similar, or more, "drag"? Enough to be significant if pedaling with the motor? off?


I test rode a Levo Expert today and something seemed a little off; it was the power. Much less resistance without the motor than my Yamaha PW-SE bike. I also like the instant engagement of the motor; it must use a roller or sprag clutch. You're lucky to own one.

I didn't really notice the extra torque of the motor; probably because it's a 29er and I have a smaller chainring on my bike. But wow; even on parking lot ride with a short excursion into a rocky catch basin and back out this bike blows me away; I want one ?.


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## 33red (Jan 5, 2016)

hikerdave said:


> I test rode a Levo Expert today and something seemed a little off; it was the power. Much less resistance without the motor than my Yamaha PW-SE bike. I also like the instant engagement of the motor; it must use a roller or sprag clutch. You're lucky to own one.
> 
> I didn't really notice the extra torque of the motor; probably because it's a 29er and I have a smaller chainring on my bike. But wow; even on parking lot ride with a short excursion into a rocky catch basin and back out this bike blows me away; I want one .


I have a 29x2.3 21 pounds with tiny rims (non Ebike)and i am wondering if the Levo with 29x2.6 is feeling like a player or a bit like a fat with those wider rims and heavier tires? I must be lucky my HT Haibike 2017 with Motor Yamaha PW-System, 250W has instant engagement. It is tough finding any small or med Levo in a shop around here maybe i will be able to try one but probably only the 5 min parking lot. I think the numbers do not mean much. With 4 assist levels i feel more power would just mean less range. A guy on a Giant also Yamaha says riding with buddies he gets 10% more range than Shimano 8000.
Giant owners feedback seems very positive with the lower price maybe i will get one full suspension but again it is pretty much sold out.


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