Monday, February 7, 2011


Most bike nerds would argee that an internally geared hub is, in theory, the ideal set-up for touring. While discussion of the exact ranges of IGHs vs. traditional derailleur systems would make this post useful it is beyond the scope of this blog, for the moment. Suffice to say, that IGHs generally do not have as much range as derailleur systems and by virtue of their fewer speeds they have larger jumps between gears. The Rohloff hub is the most advanced to date, with 14 speeds it covers more range than any other IGH. You can also skew your hub to the high or low gear range based on your cog and chainring selection. Shimano and Sram are up to 11 speeds but still do not have quite the range of a Rohloff , but they are a fraction of the price. 

Recently, I had a customer who wanted to give his 8 speed Shimano Nexus IGH equipped bicycle more range. He is riding across Canada this year and does not want to lose his high gear to by skewing his hub to the low with alternative cog and chainring combinations as he will need them to cross British Columbia. He began to ask me lots of questions about what was possible with individual parts and at first I was reluctant to entertain him. My initial reaction was that what he wanted to do was unreasonable; he would be far better off purchasing bike with derailleurs, but that was before I knew he already owned the bike. So I suggested he returned with his bike before we took it any further. I looked at his bike and ordered the parts he wanted. This is what his bike looked like to start. On chainring, one cog and an eccentric bottom bracket to tension the chain.

What he wanted to do was add multiple chainrings so he decided on a triple and I brought in a Shimano Alfine chain tensioner, a triple front derailleur and a triple crank. He came up with a Shimano MTB shifter. Everything went together surprisingly smooth. I rotated the bottom bracket to the lowest position to make his center of gravity as low as possible for maximum loaded stability. Everything adjusted and a new chain installed, it worked surprisingly well. The shortfall of this retrofit is the jump between gears remains wider than an 8 speed cassette and there are high and low gears that he will never use because they are too extreme. I am also concerned about the torque that will be generated in the extremely low gears, but he was intent on the conversion so I made it happen. It was a fun job and a cool experiment. I had to use a clamp on housing stop for the front derailleur right about the bottom bracket to make it work and I must say it all turned out pretty clean.


1 comment:

  1. The new continuously variable Nuvinci has a 360% ratio range. That would be comparable to a 10t to 36t cassette with perfectly smooth stepping.