Tips: Get It Right, Get It Tight (But Not Too Tight)
This post is intended for home mechanics. If you don't know what a horizontal dropout is, this post will be of no interest to you. If you're interested in learning, I may prepare a layman's explanation of the ins and outs of simpler drivertrains in the future. For now, Sheldon Brown's article, which requires some very active reading, will suffice.
We are lucky that most of us don't have to bother with chain tension: in all but a few cases, geared (i.e. multi-speed) and even some single-speed bikes use a derailleur, which doubles as a chain tensioner. For anyone making his or her first foray into building or maintaining bikes without derailleurs, however, wrestling with horizontal dropouts can be a considerable ordeal.
If you've got a bolt-on wheel (rather than a quick-release), Will Meister at 63xc offers a simple explanation of how to get the job done. With this method, bolt-on wheels allow you to fine tune the chain tension; quick-release wheels, while making the job immensely easier and eliminating the need for tools, do not offer that kind of precision.
Once the chain is decently tight, you may spin the cranks to discover that there are sometimes considerable variations in chain tension at different points of the rotation; Sheldon Brown has something to say about that. I have never really been able to get this method to work, but with only three years of experience under my belt, I'm not in a position to question the efficacy of Sheldon Brown's recommendations.
