Six Speed MTB

After running a single speed mountain bike in Marin, CA for the past 4 months, I have decided that it may not be for me. It is a very interesting way to ride, but it really leaves me wanting when the terrain gets fairly steep or soft, and when the downhill gets up to real speeds. I figure that I could use a little bit of range from center to make things a little more fun while keeping my drive train solid for winter riding.

While practicing for the Sea Otter Downhill race in 2006, I got to talking to a pro rider that was running a four or six speed setup. I realized that I really had to be a little more creative when thinking about what is possible when setting up a bike for specific targets. That minimal gearing setup has stuck in the back of my mind untill now. It may be perfect for what I need.

Why 1X6 instead of 1X9

Like most things drivetrain, it comes down to chain line. When I am helping a new rider learn to shift properly, one key rule that I give them is to keep their chain as straight as possible. A straight chain is one of the most efficient drive systems available for a bicycle. A straight chain is one of the factors that make a single speed bike feel quite like it does.

For this reason, a 27-speed mountain bike really only has about 12 or 15 correct gear choices. Other choices may be possible, but result in such a horrible chain line as to be inefficent or destructive. A 1X9 is really just a 5 speed with 4 additional gears that are completely destructive or inefficent to use.

So, we go down to 1X6. A 1X5 is probably better in terms of pure theory, but since I can fit six speeds on my hub, I am going to try it. With either of these setups, the chain is only shifted between 2 or 3 cogs from center, keeping a fairly efficent chain line. This also keeps chain wear down to a minimum.

Derailures

Shimano 105 Rear Derailleur RD-5600-SS