# Bafang BBSHD chain lines, chain life and gearing?



## highroad 2 (Jan 24, 2017)

I would like to mid drive my Giant Yukon fat tire bike with a BBSHD for sand dune riding.
FWIW online I have learned that it is hard to get good chain lines (CL) with a BBSHD.
The Yukons current CL is 16 mm outboard of the bottom bracket (BB) shell.
The BBSHD is 34 mm from where it would make contact with the BB shell to where the chain ring bolts on (assuming the chainstay will allow the BBSHD to slide all the way in).
The Luna Eclipse 42T has a 25 mm inboard offset, which brings the CL to 9 mm outboard of the BB shell. ( 34-25=9 mm)
If i used a Luna Mini 30t which has a 8 mm inboard offset, which brings the chain line to 26 mm outboard of the BB shell. (34-8=26)

The stock CL is 16, the 42t moves this inboard to 9 and the 30t moves it outboard to 26.
if I use the 42t then the CL is not ideal for the smaller chain rings on the cassette and if I use the 30t then the CL is not ideal for the larger inboard chain rings on the cassette.

Questions
1 I have read online where BBSHD users rave about using the luna mini 30t versus the 42t because it makes the motor much more responsive accelerating and climbing with only a few mph loss in top speed.

2 A Luna 36t has the same 8 mm offset as the 30t so exactly the same CL but a more in between gearing?

3 I have a hard time making SramNX 1 x 12 chain last on my Haibike. What chain should I use with the more powerful BBSHD?

4 Am I over thinking this project?

Thanks
Highroad 2


----------



## fos'l (May 27, 2009)

My conversion(s) were BBS02, but the same applies. 
1) If your BB is 73mm, you won't be able to use the "jam" nut to secure the motor; some have used Locktite successfully to keep the nut from loosening, but I needed to go to a bike(s) with 68mm.
2) The engine has enough power that 11-17-28 gearing - 8 speed spacing - was adequate with the Lekkie 42t or Luna 30t rings. I spaced the rings to the outside end of the cassette.
3) Lekkie cranks will resolve the discrepancy in distance between the crank arms and the chainstays.


----------



## portnuefpeddler (Jun 14, 2016)

As a Rohloff hub user, on my Surly Wednesday/BBSHD combo, any chain issues are largely in the past! A perfect chain line, no matter what gear I'm in, and a bigger and tougher chain. Riding in deep snow just now, I just put the bike in the shop and noticed the rear wheel was totally packed with snow, kinda wet heavy snow. I take it for granted now, but I think a derailleur system would have been challenged by that snow today. The BBSHD is working great also in these conditions, and has been for 3 years now. The extra power it has is much appreciated, as is the throttle, when getting started, especially when you put a foot down and the snow is knee deep.


----------



## Cody01 (Jul 23, 2014)

I had an alignment issue after my BBSHD install contacted Luna. Even though I was leaning toward the 36T mini at first since I do tight twisty hills they suggested the Eclipse so I went with that. I don't have a lot of miles yet but things seem to be going well. I have two ebikes and think that carrying a spare chain on each is the most advisable thing to do.


----------



## portnuefpeddler (Jun 14, 2016)




----------



## dundundata (May 15, 2009)

I have a Luna 48t and another 44t chainring on the way from China. They are both offset like the original ring to come in towards the bike.


----------

