Yuba Mundo new IGH install having chain issue

I am trying to wrap up my new IGH wheelset installation on my BBSHD Mundo but I can't for the life of me figure out what is wrong with the chainline. Hoping I'm missing something noobish.

I'm wondering if the sprocket that came with the kit is sized for a different chain or something. It's an 18t sprocket that appears standard and is shown in the SA site as compatible with a 1/8 chain.

Attached some pics to see if anyone has any ideas.

Build features -

Yuba Mundo - original 7-speed
BBSHD
SA RX-RK5 IGH
Shimano Alfine ct-s500 chain tensioner
Origin 8 DAT-PRO 65MM rims
Tektro Dorado 203mm
Maxxis Hookworms

bhinkle50 said:

I'm wondering if the sprocket that came with the kit is sized for a different chain or something. It's an 18t sprocket that appears standard and is shown in the SA site as compatible with a 1/8 chain.

Click to expand...

Well, bicycle chain is 1/2" chain.


If the centers of your sprocket are actually 1/2", then it could be that the sprocket teeth are thicker at their bases so the chain can't go down fully onto it, so that the centers of the chain links aren't riding at the center of the tooth gap, preventing it from seating fully all the way around the wrap. If that's the case, changing to BMX chain should be wide enough to do that, assuming you are using multispeed chain now. I think this is the most likely problem.


If they are not 1/2", you'd have to either replace it with a standard 1/2" tooth sprocket, or change all the other sprockets on the bike to match the non-1/2" sprocket, along with the chain. I think it's unlikely that this is the problem.



There's another member that posted basically the same problem but we couldn't get a final response from him:
https://endless-sphere.com/forums/viewtopic.php?f=7&t=87899

Thank you for the response. I agree that it's most likely a width issue. For some reason I thought I had a 1/8 chain, but I clearly do not. I'll be picking up one (two) today and see if this fixes it and report back.

Picked up a couple 1/8 chains and spliced them together and it fixed my seating issue. Now the tensioner I bought (ALFINE CT-S500) appears to be creating some excess drag so I'm going to track down a roller wheel type to get this set up dialed in.

Since those will be noisier/etc, why not just shorten the chain and use just the top roller on the other one, and whatever position adjustment it has (or reinvent it a tad to give it some if it doesn't have any) to take up the slack?

If all the gearshifting is in the IGH, you don't need extra chain and a two-wheel tensioner to take up the slack in it.

I use the CT-S500 chain tensioner. Definitely one of the best available, with a strong spring and long action. Ideal to instantly take the chain slack with long travel suspension action. It is designed to match a 16t or 20t rear sprocket though, if you have a smaller or larger one this may be the reason why you have a problem with it. Another possible reason is alignment, since it does need to be tuned with shims and a complete set of shim washers is not supplied with it.

Amberwolf is right, that you don't need a long action tensioner if you have no rear suspension. Its extra weight and robust construction are pointless when you don't need it. This tensioner does weight more than derailers.

The Mundo has a large double kickstand and you need to keep the chainline lower to clear it. The SA hub came with a 1/8 18 tooth sprocket, so I had to get a new 1/8th chain to make it work. The Alfine tensioner isn't rated to work with the 1/8 chain as the guides are rubbing. I could remove the guides and just use the open sprockets, but I'm getting the Surly Singleator that has a wheel with guides that can be flipped to support a 1/8th chain. I can ride it now, but it's not as smooth as I'd like.

I'll get some pics posted up when I get the setup sorted fully.