Are there standardized dimensions for mid-drive motors?

katonda

Regular
Hello,

I've been thinking about having a custom frame built and was wondering if there are already industry standards in place for mid-drive motors so I can build a frame that will outlast its motor and can be upgraded as motor technology improves (and laws change). Specifically, I'm thinking about big ebike brands like bafang and bosch with motors that look a little like:

525325

525326

525327

525328

525329

525330

I guess my question, are they interchangeable between brands or do I need to have a frame built with a specific brand or even engine model in mind?
 

raleighnut

Legendary Member
Location
On 3 Wheels
The ones you have pictured need a dedicated frame whereas you can get mid mount motors to fit a standard frame/BB,

61qvC2lqyZL._AC_SX466_.jpg
 

CXRAndy

Guru
Location
Lincs
Most of those require special bottom bracket mounts. Each manufacturer is different.

Bafang and TSDZ2 use conventional 68/73 mm threaded brackets.
 
OP
K

katonda

Regular
Thanks for the quick replies @raleighnut and @CXRAndy.

The ones you have pictured need a dedicated frame whereas you can get mid mount motors to fit a standard frame/BB,
I realize that the motors I showed require a customized frame to support this style of mid-drive motor. My question is more along the lines of, once you have a dedicated frame for this type of motor, how easy is it to exchange the motor. I'm a little worried about the stability of the attachable E-bike conversion kits on rough terrain. Does anyone have experience with these conversion kits on MTBs or gravel bikes? do they hold up to bumps, knocks, water and grime?

Most of those require special bottom bracket mounts. Each manufacturer is different.

Bafang and TSDZ2 use conventional 68/73 mm threaded brackets.
From what I can tell, you can't buy Bosch motors for DIY projects separately, which means I will need to go for a chinese brand. I will check their lineups and perhaps contact them directly to see if they expect to retain the general dimensions of the mid-drive motors. That way I can interchange the same shape motor every five or so years without needing a new specific frame every time a motor is upgraded or the laws are changed to allow for better motors without requiring plates and a licence.
 

simon.r

Person
Location
Nottingham
Does anyone have experience with these conversion kits on MTBs or gravel bikes? do they hold up to bumps, knocks, water and grime?
I’ve got a Bafang conversion on my cargo bike. I’ve only ridden it a hundred miles or so, but it seems very robust in terms of the mounting. I obviously don’t take the bike on ‘proper’ off-road rides, but it‘s certainly capable of gravel tracks - canal towpaths and the like. I think ground clearance would be an issue on rougher trails.
 

raleighnut

Legendary Member
Location
On 3 Wheels
Thanks for the quick replies @raleighnut and @CXRAndy.



I realize that the motors I showed require a customized frame to support this style of mid-drive motor. My question is more along the lines of, once you have a dedicated frame for this type of motor, how easy is it to exchange the motor. I'm a little worried about the stability of the attachable E-bike conversion kits on rough terrain. Does anyone have experience with these conversion kits on MTBs or gravel bikes? do they hold up to bumps, knocks, water and grime?



From what I can tell, you can't buy Bosch motors for DIY projects separately, which means I will need to go for a chinese brand. I will check their lineups and perhaps contact them directly to see if they expect to retain the general dimensions of the mid-drive motors. That way I can interchange the same shape motor every five or so years without needing a new specific frame every time a motor is upgraded or the laws are changed to allow for better motors without requiring plates and a licence.
Once the pedal shaft is through the BB shell I can't see it going anywhere although ground clearance might be an issue.
 

CXRAndy

Guru
Location
Lincs
The motor doesn't hang much below the chain ring. If you want an off road, Id go for the Bafang motors. They're known to be built very well.

Just so you know Bafang BBSHD is a pedal assist. That means it doesn't matter what effort you press on the pedals, you will be given a certain wattage depending on the level you've chosen

TSDZ2 is torque sensing system. It gives a proportion of power depending on how hard you press on the pedals, set by assist level
 

keithmac

Veteran
As said you'll be tied to one manufacturer (until they change form factor!).

I have a TSDZ2 and it is a good bit of kit.

If you want to got for Shimano/ Bosch/ Yamaha you'd be better off buying a complete bike.

Bosch don't even supply parts for home repair iirc let alone motors. Never seen a STEPS for sale either?.
 

samsbike

Veteran
Sorry to derail the thread slightly but what would be the recommendation for converting a Boardman mtb to an e-mtb, specifically for off road use
 
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