Conversion - Installing M500/M600 Motors in Bosch Gen 2/3 Frame

Tomblarom

Active member
Feb 3, 2021
119
185
Germany
Hi everyone, after a few days of active development I can finally ditch the Bosch Performance Line motor and fit a Bafang M560. I have designed matching 3D printed parts that fit the "standard rounding" that Bosch frame manufacturers used until 2017/2018. The steel and 3D printed parts adapt from Bosch to Bafang so that the supplied Bafang cover (MD G521.B) and the Bafang bashguard (BG G521.B) can also be easily mounted with the original screws. I will also be designing 3D printed parts for the "A version" (MD G521.A cover and BG G521.A bashguard). The motor has been positioned in CAD so that both versions can be fitted with the appropriate adaptations.

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The kit has been designed so that it can remain fitted if the motor needs to be removed for maintenance. It is bolted on with M6 shoulder bolts and 4 additional M3*8mm Torx bolts, which are identical to the Bafang bolts supplied for the cover (marked red in the picture below). The M4 screws for mounting the bashguard have the same hexagon socket as the shoulder screws.
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I also reused two of the three Bosch screws (marked in yellow). All in all, you only need the following tools for assembly: Torx 10 (3D print connector, cover), Torx 20 (Bosch screws) and 4mm square (bashguard and shoulder screws). I may replace the Bosch screws with Torx 10 and threads in the plates to optimise further.
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Yes, I use 3D printing (PETG) to attach an ebike motor. However, the important components are bolted to the frame using shoulder bolts and 3mm V2A steel plates. In the longer term, the plastic parts are to be replaced by parts made of carbon/fibreglass-reinforced material. Injection moulding would be ideal, but there has to be enough interest first... 😂 T-slot nuts are integrated into the 3D print as threads on the opposite side. To do this, you pause the print, insert the nuts and then simply continue printing:
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The kit has a very minimalist design, which means that the plates can always remain the same and only the connectors need to be adapted to the frame contour. Example of this Trek Powerfly FS 7 from 2016 (exactly this model). Here the hole spacing fits, but the contour has been adapted by the manufacturer, which means that the standard round fairing would not fit easily:
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The contours therefore differ in some cases, which means that the hole spacing may fit, but the contour may not. If you want to try it, I have a few plates left:
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The offset to the centre of the bottom bracket of the original Bosch motor mount is approximately 16.87mm towards the centre of the frame:
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Last edited:

Jeromep

Member
Mar 17, 2022
31
7
Florida
who would want to swap a bosch motor with a bafang? is this common or is it an inability for consumers to buy bosch motors themselves?
 

Tomblarom

Active member
Feb 3, 2021
119
185
Germany
who would want to swap a bosch motor with a bafang? is this common or is it an inability for consumers to buy bosch motors themselves?
Sometimes you can get old Bosch frames for cheap on marketplaces. Or your Bosch motor is dead and the frame is still ok and the geometry is just right for you. Bosch is not providing any replacement parts or new motors directly to consumers. Bafang is easygoing in this regard.

Most people that contact me, know that their frame is Bosch and want Bafang. It's rather a decision and active interest to make the switch, rather than an "inability" to distinguish a Bosch frame from Bafang ;)

And waiting for a carbon frame from china, having to deal with customs and the chinese mentality isn't for everyone. Some just want to ride, not wait 😁
 

G-Sport

Active member
Oct 7, 2022
291
227
Yorkshire
This is super interesting, thanks for sharing. So the BB gets a little higher and the chainstay gets a bit shorter and seat-tube steeper? win win win!
3D print services for aluminium are pretty cheap now if you want to look at doing the adaptor that way.
 

Sgarth42

Member
Oct 13, 2021
72
49
York
I'm fully behind the idea of adaptor systems. BOSCH do not support the maintenance/repair of the motor systems by the end user, nor do they allow end user access to the firmware to allow easy upgrades for alternative displays, battery packs etc. It's a closed system. So when my Bosch Gen 4 gives up ( hopefully not for a long time ) I would like to think I can install an alternative. My 1st Bosch motor had to be replaced after just 50mls from new which didn't fill me with confidence for its longevity
 

Tomblarom

Active member
Feb 3, 2021
119
185
Germany
So when my Bosch Gen 4 gives up ( hopefully not for a long time ) I would like to think I can install an alternative.
Unfortunately, I can't supprt Gen 4. It's way to small for M500/M600/M510/M560 motors. M820 could fit, but it's an downgrade, since only reason to take Bafang is the power and accessibility of replacement parts. M820 is way to new... Can only imagine how many issues it has, currently. It took Bafang over a year to fully optimize M510, to a state where it's usable. M560 is currently very bad and has an overshoot to the moon. And the thumb throttle is aweful.. 😑 So bad accelleration.
 

Sgarth42

Member
Oct 13, 2021
72
49
York
I'm hoping my bosch motor will last a good while longer yet as it's less than 12 months old. Hopefully by the time it dies there will.be viable alternatives ( assuming aftermarket components don't become available for bosch motors in the meantime).
 

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