# Alfine 8 chain line



## Jvan_wert (Apr 8, 2007)

I need yall's experiance and advice with my chainline and shifter on my bike. Took it out on a local trail for the first shake down and had a problem with the chain falling off so I did the search thing and found that I may have had the spocket on the hub wrong. So I flipped the sproket but now it is super close to the shift cable bracket. I bent the bracket out just a schoach and it looks kinda okay but I am still a little worried. The bike is an 11' Karate Monkey with an Alfine 8 rear hub, shimano tandom captian crank that has been drilled out and new theads inserted and flipped so that the chain ring is on the right and a Sram PC-1 chain. I have the cable running along the seat stay instaed of the chainstay. Running the cable along the chainstay is not a vable option. Thanks in advance for any advice or suggestions.


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## sealcove (Apr 26, 2004)

Looks about right. Alfine chain line is always a problem for MTBs. Flip the cog so to push the chain line away from the hub; bend the cassette to clear this orientation, especially if you need to route via seat stays. 

Looks like you have a hard tail with horizontal dropouts... should not have problems with losing the chain if you pull the rear wheel back and keep the chain tensioned.


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## Leopold Porkstacker (Apr 21, 2010)

If you are just running a single chainring up front, you could opt for some of those 1.5 - 2mm thick chainring spacers (make sure your chainring bolts are long enough) and just flip the Alfine cog around again.


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## Jvan_wert (Apr 8, 2007)

First time the time the chain started falling off I found that the drive side axle nut was snug but not really tight. The second time was when I had a pinch flat and did not get the chain tight enough. I only worry that I'm getting the chain to tight and that I'm going to cause a lot of wear to the drivetrain. The pictures are after I flipped the sprocket so that it is futher away from the hub centerline


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## pursuiter (May 28, 2008)

There's no substitute for an actual chainline measurement. Do you own a pair of measuring calipers? 

"shimano tandom captian crank " 

I have a few sets of those, what bb did you use? What spindle length?


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## Velobike (Jun 23, 2007)

Is it a chainring designed for a derailleur? If so it is designed to have the chain slip off easily.

Use a chainring designed for a single speed because it will have higher teeth. Surly make some good ones.


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## Jvan_wert (Apr 8, 2007)

Came with the crank it is a tandom captian's crank that has been flipped around. The problem is not with the chain ring, the chain jumps off at the sprocket. I flipped the spocket and installed a new bottom bracket. It put the chain ring super close to the seat stay but now my chain line is much better.


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## pursuiter (May 28, 2008)

Jvan_wert said:


> Came with the crank it is a tandom captian's crank that has been flipped around....


I have a set of those. You are using the inner ring lands, your BB spindle should be ~127mm to have a 47mm chainline on the inner ring lands.


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## Jvan_wert (Apr 8, 2007)

pursuiter said:


> I have a set of those. You are using the inner ring lands, your BB spindle should be ~127mm to have a 47mm chainline on the inner ring lands.


how do you like it? It is definitely a stiff crank. I needed 42 mm to line up with the hub. I'm using a 73X122 BB. Not sure where you found that number or did you measured it out. With some not so fine measuringing and a little rough math I figure I'm around 44-45ish at the crank.


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## pursuiter (May 28, 2008)

I liked the cranks better when there weren't lots of slight used external bb cranks on ebay. He raised his prices too, a few years ago it was ~$40 shipped for the cranks with 38T chainring. Now it's $52 for the crankset and $23 for a UN-52 bb. For $75 I'd rather search ebay for an slightly used external bb crankset. I find it much easier to adjust the chainline on an external 68/73mm external bb, esp if the frame is 68mm. I had one of the heilcoil inserts fail, he fixed it no charge, I paid shipping to him.

OK, I had to look at a few bikes to remember what I had. These measurements are for those cranks on a Shimano UN-54 bb:

118mm = 46.5mm CL on the inside lands, this is ~ perfect for the cog dish outward (actual CL=46.8 for Alfine/Nexus)

122mm = 48.5mm on the inside lands, you're off by ~2mm by my calculations.

To measure CL accurately here's how I do it:
- 1st; measure diameter of seat tube, divide by 2 to get half the diameter of the seat tube
- 2nd; measure from the left side of the seat tube to the middle of the front chain ring
- 3rd; subtract half the diameter of the seat tube from the 2nd measurement.

This technique gives square edges to measure from, I can't estimate the middle of the seat tube very accurately esp when I need better than 1mm accuracy.


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