Hi guys, I see comments about the "drag" that Bosch Performance Line motors produce compared to some competing hardware out there and I wanted to clarify with my understanding and invite you to share:
My understanding is that the only drag produced on Bosch Performance Line motors is the reduction gear in the bottom bracket. It won't slow you down from coasting faster but does produce a bit of friction while pedaling because the chainring has to spin 2.5x for each crank revolution. I think some people hear "drag" and think the bike won't coast just as efficiently or be able to pedal above 20 mph and that is not the case at all, even if the motor is turned off. My experience has been that the motor doesn't pedal quite as efficiently because of the 2.5x conversion and in my experience the resistance is minimal. The benefits however are mechanical advantage for efficiency of motor operation, improved chain retention, and possibly improved ground clearance. Does this sound accurate to you?
Again, I am spelling this out and inviting conversation because I think there is confusion and misinformation around why electric bikes can feel difficult to pedal beyond 20 mph (or 28 mph if it's a Class 3 speed pedelec) and my experience is that the combination of wind resistance and a feeling of "slowdown" as the motor fades out can create the illusion of "drag" but the only real drag happening is when you turn the crank arms and it converts each pedal stroke into a 2.5x chainring spin. Again, this is unique to the Bosch Performance Line motors but is not present on their new 2018 Active Line product. That motor tends to be more gentle and allows you to pedal backwards and actually move the chain (though there is some friction when doing so).
Competitors like Brose advertise that their motor has a built-in freewheel so that you can pedal faster than the motor or without the motor and nothing inside will be turned. That's a neat feature and is made possible by the full size chainring design. I'm not saying one is better than the other, just that the "drag" some people refer to might be exaggerated. I frequently surpass 20 mph while pedaling on flats and have even reached 40+ mph when coasting down hills on Bosch Performance Line motor powered electric bikes. What you do get from this company is durability according to the shops I visit who carry multiple brands, a universal and backwards compatible battery design (at least with the Powerpack models), and a great warranty with a dedicated service partner in the US.
Yes, I'm a bit of a Bosch fanboy because they were one of the first high-quality ebike brands to enter the USA, but I have also owned Brose powered electric bikes, hub motors, and other friction drive systems. Nobody paid me to write this guide, I simply wanted to share my experience and invite input
The photo below shows a unique design where the smaller chainring on a Bosch Performance Line motor is next to a full sized chainring on a tandem electric bike. I think it demonstrates the unique sizing differences and shows how the smaller chainring has to spin faster in order to move the chain the same distance as the full sized chainring, the internal gearing that makes this possible is what produces a bit of friction but your still have a big mechanical advantage against this friction because of the length of your crank arms (usually 170 mm in length). Many times the Bosch chainring is obscured by an alloy protector or plastic cover, so this photo lets you see a bit closer:
My understanding is that the only drag produced on Bosch Performance Line motors is the reduction gear in the bottom bracket. It won't slow you down from coasting faster but does produce a bit of friction while pedaling because the chainring has to spin 2.5x for each crank revolution. I think some people hear "drag" and think the bike won't coast just as efficiently or be able to pedal above 20 mph and that is not the case at all, even if the motor is turned off. My experience has been that the motor doesn't pedal quite as efficiently because of the 2.5x conversion and in my experience the resistance is minimal. The benefits however are mechanical advantage for efficiency of motor operation, improved chain retention, and possibly improved ground clearance. Does this sound accurate to you?
Again, I am spelling this out and inviting conversation because I think there is confusion and misinformation around why electric bikes can feel difficult to pedal beyond 20 mph (or 28 mph if it's a Class 3 speed pedelec) and my experience is that the combination of wind resistance and a feeling of "slowdown" as the motor fades out can create the illusion of "drag" but the only real drag happening is when you turn the crank arms and it converts each pedal stroke into a 2.5x chainring spin. Again, this is unique to the Bosch Performance Line motors but is not present on their new 2018 Active Line product. That motor tends to be more gentle and allows you to pedal backwards and actually move the chain (though there is some friction when doing so).
Competitors like Brose advertise that their motor has a built-in freewheel so that you can pedal faster than the motor or without the motor and nothing inside will be turned. That's a neat feature and is made possible by the full size chainring design. I'm not saying one is better than the other, just that the "drag" some people refer to might be exaggerated. I frequently surpass 20 mph while pedaling on flats and have even reached 40+ mph when coasting down hills on Bosch Performance Line motor powered electric bikes. What you do get from this company is durability according to the shops I visit who carry multiple brands, a universal and backwards compatible battery design (at least with the Powerpack models), and a great warranty with a dedicated service partner in the US.
Yes, I'm a bit of a Bosch fanboy because they were one of the first high-quality ebike brands to enter the USA, but I have also owned Brose powered electric bikes, hub motors, and other friction drive systems. Nobody paid me to write this guide, I simply wanted to share my experience and invite input
The photo below shows a unique design where the smaller chainring on a Bosch Performance Line motor is next to a full sized chainring on a tandem electric bike. I think it demonstrates the unique sizing differences and shows how the smaller chainring has to spin faster in order to move the chain the same distance as the full sized chainring, the internal gearing that makes this possible is what produces a bit of friction but your still have a big mechanical advantage against this friction because of the length of your crank arms (usually 170 mm in length). Many times the Bosch chainring is obscured by an alloy protector or plastic cover, so this photo lets you see a bit closer:
