wesmamyke

So actually having some experience with a Bafang mid drive kit the Q-factor issue was worse than I thought. I built a kit for someone else, an older one with square taper cranks. Works great, even with the terrible chainline. Also very little noise, quieter than a new off the shelf bike with Bosch stuff for sure.

I've seen the heavilly dished after market Luna sprockets that overhang the motor housing, or I guess the gear housing? Those seem to solve the chainline issue pretty well.

But that Q-factor, totally unrideable by me anyway, my knees are just not up for that. Is there any kit that has just normal-ish width cranks? Even mountain triple width is fine, nothing crazy narrow. The unevenness though is the real problem, again anything solving the issue?

Obviously the built in Bosch unit pretty much handles it, but the price is just way out there for even the most basic complete bike. I also have a really good bike here to convert if I could figure out the couple issues I have.

Thanks for any input you might have.

Nightdiver

There are cranks that are meant to even out the Q-factor, such as the Lekkie crank arms, but if I understand them correctly, they actually make the Q-factor wider! There are crank arms for the TSDZ2 that are meant to even out the Q-factor and make it narrower by about 20mm. Not sure if these work on the Bafangs or not though. I'm sure the square taper is the same, but not sure if there is any interference with the motor housing.

wesmamyke

I experimented with crank arms we had lying around when I was installing the Bafang. One of the original cranks off the bike actually would have evened out and widened the Q-factor, but they wanted the kit installed as it came to keep the matching black cranks.

2old

Lekkie cranks on my BBS02-equipped hardtail resolve the difference in distance from the arms to the chainstays, and the "Q" factor doesn't bother me. The Revel Propulsion kit doesn't have the problem (AIR from testing it).

wesmamyke

I'm leaning towards a Tongsheng unit at the moment. Although I still can't find any actual measurements taken by anyone for Q-factor. There is vague information, but it's in reference to the Q-factor as a whole, not each side.

Anyone know the actual spindle lengths on Bafang, and Tongsheng drives? And maybe any offset they have? I can probably figure it out from there. Thanks.

Leisesturm

The Tongsheng and Bafang mid-drives are all there is. And the Q-factor is about the same for both. I'm leaning towards the Tongsheng unit myself. I plan to get the modified right hand crank that evens (but cannot eliminate) the wider Q-factor. I suspect that like a lot of ergonomic issues (crank length, saddle tilt) the theory is different from the practice or what you notice on a short ride. On an e-bike the knees should not be subjected to as much stress unless one spends all their time riding without the assist on (why?). There is a seller of both the Bafang and Tongsheng systems (David Hall) who appears to have gone above and beyond where most re-sellers of these kits go. He is the person you want to ask about dimensions and offsets etc. but my advice is not to worry about it. Seriously. It is a non-issue. Mainly because it is what it is. If you want a mid-drive, the wide q-factor is the price of admission, and thousands upon thousands of riders pay up and don't seem any worse for wear. I'll risk it.
Edit: note the crank options

wesmamyke

So the Tongsheng TSDZ2 appears to have a 150mm spindle for anyone else looking for the information.

Offset to the drive side obviously, not sure of the exact amount yet. Seems to be 10mm or so.