Sunday, August 9, 2009

Gearing Up

I had a little minor surgery in July so I've been away from this blog for a while. I'm recovering nicely and was able to get in a short ride on the Oregon over the weekend. It felt good, but i don't have all my strength back yet. During my hiatus, it occurred to me that this would be a good time to make a change on the back-to-back that I've been thinking about for the last few weeks.

The bike has 3 speed Sachs hubs on both ends. My stoker and I have noticed that we typically spend all our riding time in 3rd gear unless we're climbing. Then we drop down to 2. Neither of us have ever used 1. When the bike is going downhill, we can't keep up with it and are unable to apply power, even in top gear. On flats our speed is limited not by leg power, but by our ability to spin fast enough to keep up with the bike. In short, the bike is geared too low for us. The other problem we've noticed is that in top gear, my stoker is always spinning a little faster than I am. No, I can't see her back there, but at times, I can see her shadow on the side of the road and observe her cadence.

So I decided to run the bike over to Danny, the Cycle Genius, to see if he could up gear the bike for us.

As usual, Danny came up with a solution. He removed the old drive chain rings above the derailleurs and replaced them with larger ones. This isn't as simple as it sounds. The old chain rings were 48 teeth in the front and 46 teeth in the rear. This explains why the stoker spins faster. Both chain rings are now 54 teeth. As a practical matter it may be necessary to fit a floating idler on the front (ala my Oregon)to be sure the chain aligns properly in all gears.

In back it was necessary to raise the rear idler so that the chain would clear the new, larger chain ring. This meant taking the idler off of it's frame mount and moving it up to the rear handlebar stem. The height has to be adjusted carefully since these are flip-it handlebars.
This new configuration should provide better utilization of the gearing rage of the bike. It should also allow for better speed. I can't wait to get the bike back out on the road, but that will be at least a couple of weeks.