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.
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
As is the case with 99% of the questions on this site, Sheldon Brown has an answer for us.
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.