The idea of a single speed bike is that it is supposed to be simple, uncluttered and open up a whole new world of freedom when cycling. None of those pesky gears to make it easier to go up hills or so you can go faster going down hill. Vast expanses of bar space for your squeaky horn or coffee cup holder. Freedom!!! and it's simple.....WHOA, not so fast, is it really simple? Maybe because you don't have to set up a deraileur it may seem simple....BUT IT'S NOT!!. The beauty of a geared set-up is the spring loaded arm on the deraileur that tensions the chain, who cares if the chainring is round...the deraileur will suck it up. Also, a standard mountain bike has vertical drop outs, there shouldn't be any question whether the wheel is straight.
In building, riding, tuning and maintaining my Single Speed bike, i have discovered that some of these items add a whole new degree of frustration to a bike that is supposed to be simple. Tolerance on Chainrings, cranksets is HORRIBLE. My chain will go from super tight to super slack in one rotation. This is even on chainrings manufactured specifically for SS use. come on folks, I'm not asking for a concentricity of .0001...but at least try to get it close so that the tension is consistent through a revoloution. Who knew this would be such an issue, before i read a blurb on the Park Tools website that pointed out that chainring manufacturers do their technical drawings with crayons and no rulers, i was struggling to figure out why the heck the chain tension on my bike fluctuated so much. I switched chainrings, rear sprocket, crankset, bottom bracket, chain....what a pain. The other thing with the SS with sliding dropouts is making sure the wheel is straight. Not really a big deal, but a regular bike doesn't have this problem. I had to break out the builder's square to get it close to centered. Hopefully everything stays put. I guess if i want a truly simple bike, i need one of those "like a bikes".