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I have a Bullit cargo bike. It has a Shimano 39t chainring and a Alfine 8 rear hub. I was going to go for a Rohloff to get more gears, but the price is just getting stupid. I looked at the Alfine 11 but its lowest gear is reported to be the same as the Alphine 8 and I need lower gears to get me up hills. So I have now turned my attention toward buying a smaller chainring that will fit the 68mm HollowTech ii. But I have been thrown by the discussions about chain sizes. If I purchase a chainring with say an SLX 40,28T or Delore 38T,24T would this mean than my normal 1/8th chain would get stuck. fall off etc. And can you use a Deraillia shifter on a front chainring while keeping the rear hub? I am trying to keep my top speed but also obtain lower gears for the hills. I have used the Bullit to carry camping gear and my dog for many trips but now want to tackle some real mountains.

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    When you add a crank with 2 chainrings, you are going to need some way of accommodating the difference in chain length when you shift from one chainring to the other. You will need a chain tensioner (like this: amazon.com/Shimano-Alfine-Chain-Tensioners/dp/B003UW64N2) You should check if your bike has a way of installing one of those. Maybe if you read the Amazon reviews for that item, you can learn more about your situation. – Nik Mar 14 '15 at 18:01
  • Thank you for this. Have been reading the reviews and understand why I would need a tensioner. Common sense really. The Bullitt's frame is designed for a cassette and there is a fixing spot for the tensioner. – David May Mar 14 '15 at 22:37
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From what I've read about the Alfine 11 and 8, the lowest ratio is about the same, but the Alfine 11 has a greater highest ratio. So you could use an Alfine 11 and a smaller front chainring. Then your top gear would remain about the same, and your lowest gear would get lower. Try this site for comparing gear ratios, I have found it to be extremely useful: http://www.ritzelrechner.de

This link will take you to a comparison of Alfine 8 + 39T and Alfine 11 + 33T: http://ritzelrechner.de/?GR=SA11&KB=33&RZ=20&UF=2125&TF=90&SL=2.5&UN=KMH&GR2=SNI8&KB2=39&RZ2=18&UF2=2125

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  • Thank you again Nik for adding the comparison site for both hubs. Have been playing with it for some time. Have not decided what to do yet, going to sleep on it. I think it is a choice between buying the 11 with a single chainring, or keeping the 8 and adding two chainrings with the tensioner. – David May Mar 14 '15 at 22:41
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As is the case with 99% of the questions on this site, Sheldon Brown has an answer for us.

http://sheldonbrown.com/org/otb.html

A 63 speed bicycle.

My recollections from previous discussions about this topic is that you need to be careful to not get too low a gear ratio; if you get the front chainring very small you can have problems with stripping the planetary gears in the Alfine hub.

BTW, it is extremely unlikely that you have a 1/8 inch chain. Shimano generally recommends 9spd 3/32 chain for use with Alfine hubs.

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  • Have checked Sheldon's site twice but now thanks to you have found what I need. I especially liked how he converted cassette into a 3-speed hub - and still had a three chain ring in the front. Thank you for you valuable insight. – David May Mar 14 '15 at 22:39

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