Please help which chainring?

[rhb]

I need help finding a new 30 tooth chainring (front sprocket) for a 2023 Rambo Nomad Bafang BBSHD? I can't figure out which one will fit? Rambo is sold out.

 

[Rich W.]

Find the specs for the bike. You’re looking for the BCD - bolt circle diameter. So if its a four bolt chain ring and the specs say its a 30T104BCD just about any 4 bolt 104mm bolt circle diameter chain will fit. So you need that spec.

 

[rhb]

thanks

 

[rhb]

I did not know that, I will check

 

[rhb]

Ok!
So I took off the chainring and measured it tonight. Best I can tell, it is 112mm BCD.
4 bolt. Round. It is 36 tooth. I want 30 tooth although it may be too small to fit the adaptor that Rambo has that bolts to the BBSHD motor.
I literally can't find one ANYWHERE!!! Rambo says that are sold out.
Ideas??? for aftermarket?

 

[Admin]

Ok!
So I took off the chainring and measured it tonight. Best I can tell, it is 112mm BCD.
4 bolt. Round. It is 36 tooth. I want 30 tooth although it may be too small to fit the adaptor that Rambo has that bolts to the BBSHD motor.
I literally can't find one ANYWHERE!!! Rambo says that are sold out.
Ideas??? for aftermarket?

Great job finding the measurements for your stock part. I believe that Lekkie makes custom chainrings that fit the Bafang mid drive motors. I think they are Australian... so if you're in North America, check out Luna Cycles. I believe that they make custom chainrings that work as well. If you do step down to a smaller chainring, keep in mind that your chain length will probably need to change too. Hope this helps

 

[Rich W.]

you might get away with it with a 6 tooth change. I can tell you from experience that 8 is too much.

 

[rhb]

thanks guys...
why is 8 too much? are you talking about chain length?

 

[Rich W.]

thanks guys...
why is 8 too much? are you talking about chain length?

Yes, I went from 36 to 44 and could no longer use my 42t rear cog because the chain was too short. 8 teeth results in a big change in circumference. So I imagine going the other way it would be too long causing the problems inherent with that situation. But you can certainly experiment - wont hurt anything.

 

[rhb]

Thanks guys. I spoke with Rambo bike who helped me greatly...I think.

 

[DasTero5.0]

Yes, I went from 36 to 44 and could no longer use my 42t rear cog because the chain was too short. 8 teeth results in a big change in circumference. So I imagine going the other way it would be too long causing the problems inherent with that situation. But you can certainly experiment - wont hurt anything.

Rich, How many extra chain links do you think you will need to correct this?

 

[PedalUma]

I have never heard of 112 BCD, it must be the 110 standard. New ring = new chain. Go for a 10mm offset chainring. That will bring in the chain line so you can hit the low gears without cross chaining. This bike came in with the offset flipped the wrong way. I fixed that and gave it the thru frame treatment.

 

[rhb]

BBSHD. I ordered a Luna mighty mini 30 tooth. Still not here yet. I'll let you know.
The 36 chainring on it now with the 42 on the rear cassette will pull me at 225 and a cart with 150lbs of sand bags up a steep small off-road hill with no pedaling at all. But It still has too fast a top end in the woods!