Chainline and offset chainwheel query - Tongsheng TSDZ2B

[Pasley69]

I tried a Tongsheng TSDZ2B setup on my hardtail mountain bike.

All works OK except for one problem: the straight chain line runs to between the second and third smallest rear cogs. I am using no spacers and the motor is mounted as far to the left as it will go. This leads to severe cross-chaining and chain drop - I can only use five or six of the smallest cogs.
My bike is ten speed, the rear dropout spacing is 135mm and the provided chainwheel is 42 teeth.
I could use a narrow/wide chainwheel but I would expect this only to add maybe two more gears.
I was also thinking of an offset chainwheel - maybe 5mm with the same tooth count. I could get a greater offset if I go for a smaller diameter, perhaps 10mm offset with 32 teeth; but then it may not clear the motor housing.

Does anyone have knowledge of what is the smallest offset chainwheel one can put on one of these motors. Hopefully that plus a decent chain guide will be enough to get me the full set of cogs in use.

 

[Annieolnie]

Hi, what is the size of your bottom bracket? Is there some reason you are not using spacers on the midrive?

 

[Unicorn]

...All works OK except for one problem: the straight chain line...

Using an IGH or a single speed is the only way to have a continuous, straight chain line with a mid-drive. You can easily adjust the chain line by shimming the motor in the bottom bracket, but it's only suitable for a single gear. Combining a mid-drive with an IGH produces the best possible ebikes.

Stay safe.

 

[Annieolnie]

Using an IGH or a single speed is the only way to have a continuous, straight chain line with a mid-drive. You can easily adjust the chain line by shimming the motor in the bottom bracket, but it's only suitable for a single gear. Combining a mid-drive with an IGH produces the best possible ebikes.

View attachment 19184

Stay safe.

I have a BBs02 on an older Kona Mtb. My front sprocket is aligned with the middle of my rear cassette and all eight speeds work perfectly. It is simply not, "only suitable for a single gear".

 

[Unicorn]

I have a BBs02 on an older Kona Mtb. My front sprocket is aligned with the middle of my rear cassette and all eight speeds work perfectly. It is simply not, "only suitable for a single gear".

You're right; I should have said, "Only suitable for an IGH or single gear" if you want to use those gears fully and with minimal wear. I said, "Using an IGH or a single speed is the only way to have a continuous straight chain line with a mid-drive," which is true. Chain flex on a mid-drive with an open gear cluster destroys drivetrains. It CAN be done, but it's not optimal. Like using a chainsaw motor on a bicycle, it CAN be done, but...

Stay safe.

 

[Pasley69]

Hi, what is the size of your bottom bracket? Is there some reason you are not using spacers on the midrive?

Bottom Bracket is the common British 68mm width.

I am not using spacers on the right hand (chainwheel) side since any spacer is going to push the chainwheel even further out and make it even harder to reach the large (inner) cogs.

 

[Unicorn]

Bottom Bracket is the common British 68mm width.

I am not using spacers on the right hand (chainwheel) side since any spacer is going to push the chainwheel even further out and make it even harder to reach the large (inner) cogs.

Look at a Likkie Bling ring. https://lekkie.tech/product/bling-ring-bafang-chainring-01-02-46t/ They bring the chain line closer to the motor.

Stay safe.

 

[major masingil]

I installed a mid drive kit too. The tricks to the best chainline are to align the narrow wide sproket as close to the chainstay as you can and derailleur tuning. Those will allow you to use the most of your rear gears. The number of gears which will work normally is based off how far apart your chainstays are, how wide your bottom bracket is, and how close to natural you can get your motor's front sprocket. My bike has wide chainstays and 73mm bottom bracket. I needed 3 shims to push the motor out enough to clear the chainstay. I basically use 3rd gear through 8th. The chain gets louder the closer to the spokes it goes. It works but the chainline is not the same as it was before the motor. Gears 3-9 get me anywhere I need to go just fine. The other trick is realigning the derailleur. It's an art.

 

[Annieolnie]

I understand your situation better now. There is a 32 tooth adapter ring for Tongsheng. This is from Amazon in Canada. Do you think that would help?