Do Bosch motors add resistance at the class 1/3 support limit?

[AvalancheRun]

I was talking with an owner of a class 1 (US) Brose motor with Enviolo IGH and they said it was fairly easy to pedal up to 25 mph on flat ground.

Our Performance Line (75 nm) motors will shoot up to 20 mph very quickly, but even with a slight decline it is near impossible to hit 20.5-21 mph for more than a few seconds. The effort level required is sky high.

On a significant downhill we’ve gotten them up to 28 mph. Speed is accurate too as we have tested with GPS.

Do the Bosch motors impose some sort of artificial resistance?

 

[fooferdoggie]

its not the motor its the bike. the tires are a big cause but also the weight. the motor totally cuts out at 19.5mph but often the tire size is off and it cuts out sooner.

 

[Jeremy McCreary]

Our Performance Line (75 nm) motors will shoot up to 20 mph very quickly, but even with a slight decline it is near impossible to hit 20.5-21 mph for more than a few seconds. The effort level required is sky high.

On a significant downhill we’ve gotten them up to 28 mph. Speed is accurate too as we have tested with GPS.

Sounds suspicious to me. Know nothing about Bosch motors, but assuming hard, flat ground and no headwind, hard to imagine that total (air+tire) resistance at 20 mph would require "sky high" pedal effort to overcome — even with the motor off.

True, I can definitely feel the sudden resistance* when I inadvertently turn my motor off at speed. But the effort needed to overcome it is nowhere near "sky high". This is on a 65-pound hub-drive with 2.3" hybrid tires and almost upright seating, no lycra involved.

No feeling that bike's adding its own resistance when I exceed max assisted speed.

* Addendum: Meant to say that when I turn my motor off at speed, I suddenly feel ALL of the natural (air+slope+rolling) resistance at that speed — not just the part the motor was leaving to me to overcome.

Can't be sure without careful testing, but my turned-off hub motor doesn't seem to be contributing to that perceived bump in reistance in a significant way.

 

[mschwett]

it’s probably the relative increase in effort that’s so shocking. with big tires and an upright position and all that it takes maybe 300 watts to go 19mph. depending on the settings the motor might be supplying 200-250 of that, and the rider only 50-100.

same bike, it now takes 375w to go 21mph. sure, most people can pedal that hard briefly, but that’s probably 4x as hard as someone with an e-bike was pedaling at 19mph with the motor on. it feels like hitting a wall for many people, especially with a slight headwind or an abrupt power cut at the limiter. my commuter is a bit like this. i can go 25 on my acoustic road bike on flat ground with no wind for a bit, or 20 essentially forever. on my hub drive commuter eBike it feels nearly impossible to sustain 21mph!

 

[fooferdoggie]

Sounds suspicious to me. Know nothing about Bosch motors, but assuming hard, flat ground and no headwind, hard to imagine that total (air+tire) resistance at 20 mph would require "sky high" pedal effort to overcome — even with the motor off.

True, I can definitely feel the sudden resistance when I inadvertently turn my motor off at speed. But the effort needed to overcome it is nowhere near "sky high". This is on a 65-pound hub-drive bike with 2.3" hybrid tires and almost upright seating. No lycra involved. No feeling that bike's adding its own resistance when I exceed max assisted speed.

depends on your speed once you hit 20mph thigs start getting way harder. hit takes about 200 watts to get a normal road bike to 20mph and maintain it. my trek going up a 2% grade with no power took 250 watts. the gearing may not be ideal either or your in the wrong gear. or too upright so many things effect speed.

 

[fooferdoggie]

it’s probably the relative increase in effort that’s so shocking. with big tires and an upright position and all that it takes maybe 300 watts to go 19mph. depending on the settings the motor might be supplying 200-250 of that, and the rider only 50-100.

same bike, it now takes 375w to go 21mph. sure, most people can pedal that hard briefly, but that’s probably 4x as hard as someone with an e-bike was pedaling at 19mph with the motor on. it feels like hitting a wall for many people, especially with a slight headwind or an abrupt power cut at the limiter. my commuter is a bit like this. i can go 25 on my acoustic road bike on flat ground with no wind for a bit, or 20 essentially forever. on my hub drive commuter eBike it feels nearly impossible to sustain 21mph!

yep its such a change. Plus I have found the more zippy the bike feels the easier it is to put more effort into it. my older bosch power bulls with 1.5" tires is far zipper then my trek with 2.3" tires even though the trek has over 30nm more torque. even with new better tires on the trek its still not quite as zippy and I still tend to burn 50 more calories on the bulls but it does not feel like it.

 

[AvalancheRun]

it’s probably the relative increase in effort that’s so shocking. with big tires and an upright position and all that it takes maybe 300 watts to go 19mph. depending on the settings the motor might be supplying 200-250 of that, and the rider only 50-100.

same bike, it now takes 375w to go 21mph. sure, most people can pedal that hard briefly, but that’s probably 4x as hard as someone with an e-bike was pedaling at 19mph with the motor on. it feels like hitting a wall for many people, especially with a slight headwind or an abrupt power cut at the limiter. my commuter is a bit like this. i can go 25 on my acoustic road bike on flat ground with no wind for a bit, or 20 essentially forever. on my hub drive commuter eBike it feels nearly impossible to sustain 21mph!

I was surprised to hear that the Class 1 Specialized Como owner was able to get to 25 with ease. That bike is around the same weight, and with even wider tires.

Sounds suspicious to me. Know nothing about Bosch motors, but assuming hard, flat ground and no headwind, hard to imagine that total (air+tire) resistance at 20 mph would require "sky high" pedal effort to overcome — even with the motor off.

I'm a pretty experienced cyclist, enough to ride up 12% grades pretty easily on my acoustic, and sustain 25 when I want. Like @mschwett said about his hub drive ebike, 21 mph sustained is just not happening. My legs will sooner fall off!

 

[AvalancheRun]

True, I can definitely feel the sudden resistance when I inadvertently turn my motor off at speed. But the effort needed to overcome it is nowhere near "sky high". This is on a 65-pound hub-drive with 2.3" hybrid tires and almost upright seating, no lycra involved.

Actually, when I cut the pedal assist off going around 15 mph, I can fairly easily get to 20 from there. I started doing that to save power and get a little more of a workout.. Now to test how fast it will go completely off...!

 

[Jeremy McCreary]

depends on your speed once you hit 20mph thigs start getting way harder. hit takes about 200 watts to get a normal road bike to 20mph and maintain it. my trek going up a 2% grade with no power took 250 watts. the gearing may not be ideal either or your in the wrong gear. or too upright so many things effect speed.

Very familiar with power and resistance principles and calculations. But I'm reporting an observation here, not theory: At my preferred cadence, it does NOT take "sky high" effort to keep my hub-drive going 20 mph on hard, flat pavement with no headwind in upright position in street clothing on hybrid tires with the motor off.

Noticeable effort, definitely. Sky high, no. And my cycling strength is so-so at best. My earlier comment assumed that the OP knows how to manage cadence.

So, I wouldn't expect the OP to hit a HUGE resistance wall when the assist cuts out above 20 mph. Big bump in perceived resistance yes, sky high effort to overcome it, no. And that makes me wonder about the bike.

 

[fooferdoggie]

Very familiar with power and resistance principles and calculations. But I'm reporting an observation here, not theory: At my preferred cadence, it does NOT take "sky high" effort to keep my hub-drive going 20 mph on hard, flat pavement with no headwind in upright position in street clothing on hybrid tires with the motor off.

Noticeable effort, definitely. Sky high, no. And my cycling strength is so-so at best. My earlier comment assumed that the OP knows how to manage cadence.

So, I wouldn't expect the OP to hit a HUGE resistance wall when the assist cuts out above 20 mph. Big bump in perceived resistance yes, sky high effort to overcome it, no. And that makes me wonder about the bike.

who knows what he thinks sky high is? Also cadence plays a big part the faster you can peddle the more torque you can apply with less effort. I can measure the torque so I know what is going on.

 

[Jeremy McCreary]

who knows what he thinks sky high is? Also cadence plays a big-art the faster you can peddle the more torque you can apply with less effort.

Agree, it may well come down to the OP's definition of "sky high".

 

[AvalancheRun]

Guys, don't get hung up over that one word. I can much more easily hold 25+ mph, or climb a 12% grade with my acoustic bike than hold even 21 mph, let alone higher on my Bosch class 1.

It requires enormous and unsustainable effort! Clear? I have tried several different gearing ratios / cadences.

 

[Jeremy McCreary]

Guys, don't get hung up over that one word. I can much more easily hold 25+ mph, or climb a 12% grade with my acoustic bike than hold even 21 mph, let alone higher on my Bosch class 1.

It requires enormous and unsustainable effort! Clear? I have tried several different gearing ratios / cadences.

Now that the group has a better understanding of the effort required above 20 mph, maybe we can get back to the original hardware question: Is this normal Bosch behavior or could something be wrong with the bike?

 

[JRA]

Undo the chain and spin the cranks. If there is some resistance felt that is part of the effect you are feeling along with the added system weight over your meat bike.

Brose are known for their relative lack of resistance in the final drive due to the use of an internal belt rather than gears that mesh which cause more friction. However it is interesting in that the Enviolo hub paired with it on your friends bike is known to have some internal resistance as most IGH do. Maybe there is some Bosch magic going on that over the regulated limit of 20mph does some sort of back feed but I don't have experience with that, just a guess? Que the Bosch faithful......

 

[wildtrak]

Same with the walk assistance. As soon as I turn it off, it is getting really hard to push the fully loaded bike with the trailer up a hill.
Almost feels like it sticks to the planet, don't know if there is some magic force in the Bosch motor doing that.
But I don't have that "motor resistance" on the touring bike when riding on a smooth road with a well lubed chain and rock hard skinny tires. Going in Tour mode, I hardly notice it when the motor cuts off at 20Mph, especially when there is just a little tail wind.

 

[Stefan Mikes]

it’s probably the relative increase in effort that’s so shocking. with big tires and an upright position and all that it takes maybe 300 watts to go 19mph. depending on the settings the motor might be supplying 200-250 of that, and the rider only 50-100.

same bike, it now takes 375w to go 21mph. sure, most people can pedal that hard briefly, but that’s probably 4x as hard as someone with an e-bike was pedaling at 19mph with the motor on. it feels like hitting a wall for many people, especially with a slight headwind or an abrupt power cut at the limiter. my commuter is a bit like this. i can go 25 on my acoustic road bike on flat ground with no wind for a bit, or 20 essentially forever. on my hub drive commuter eBike it feels nearly impossible to sustain 21mph!

That is the only proper explanation. The rider of a powerful e-bike is assisted with the power of a pro cyclist and suddenly that power is cut off. It is called the 'hitting the wall effect'. That effect is far less pronounced on lightweight e-bikes such as Vado SL, or even less pronounced on a Creo SL. As the Euro e-bikes cut off at 15.5 mph, getting past the speed limiter only results in the sensation of suddenly stiffened thighs but there is no 'hitting the wall' for the Specialized SL e-bikes. With a heavy, wide tyre e-bike going past the speed limiter makes the impression the motor offering additional resistance, which is not the fact. Also, going from high to low assistance level on a heavy e-bike gives the sensation of being "pulled backwards".

No, the current Bosch (and other mid-drive) motors do not create any additional resistance.

 

[pmcdonald]

Bosch claim the new SX has 50% less resistance than the CX, so these motors are clearly adding some drag to the equation. Shimano made a similar claim with the EP8 vs the E8000.

I can feel more pedal resistance on my EP8 than my Yamaha, even taking into account the more aggressive tyre setup on that bike.

I don't think you're imagining it. Yes, there's a brick wall effect beyond the limiter. But from the manufacturers own marketing there's drag at play as well. What the penalty in watts is I have no idea

 

[fooferdoggie]

Bosch claim the new SX has 50% less resistance than the CX, so these motors are clearly adding some drag to the equation. Shimano made a similar claim with the EP8 vs the E8000.

I can feel more pedal resistance on my EP8 than my Yamaha, even taking into account the more aggressive tyre setup on that bike.

I don't think you're imagining it. Yes, there's a brick wall effect beyond the limiter. But from the manufacturers own marketing there's drag at play as well. What the penalty in watts is I have no idea

here is the second Gen motor.

 

[wildtrak]

Bosch claim the new SX has 50% less resistance than the CX, so these motors are clearly adding some drag to the equation. Shimano made a similar claim with the EP8 vs the E8000.

Anything that moves has some resistance of some kind. Bearings just lower the resistance pretty well, but still have some resistance. And when they are rusty, they add some more resistance.

There are people claiming they can feel the drag of a hub dynamo.
Sure, if you can only pedal 20 Watts, you will feel a 4 Watts drag.

Like my ebike buddy. We are riding the exact same titanium bikes with the Bosch. He is pedaling 40 Watts average what I call "pedaling air". So on a flat road, he is not moving at all until he puts it in Tour. While I am pulling a 130 pounds trailer, I still keep it off and have to slow myself down to not lose him.
So yes, he will definitely notice when the motor is off. But I don't think it is the motor's fault. He just has weak legs.

 

[AvalancheRun]

Did some more tests. I can get the bike from 0-20 mph unpowered *relatively* easily and sustain 20. 21-22 is still impossible.

When trying to get past 20/21 I peak around 600 watts. Probably not a huge number compared to real cyclists, but it still seems weird that my cut off is exactly at the class 1 limit. Granted I need to hop back on my acoustic bike which I've neglected for months. The difference in the workout is incredible!