NOTE: This article is now maintained at http://bedno.com/fixie


For the unfamiliar, "fixie" means fixed gear bicycle. Fixies are SINGLE SPEED bikes, which means no gear shifts at all nor attending cables and mechanisms. But fixies take it a step further and don't even have the "freewheel" mechanism which provides "coasting" in other common bikes. That basic fact that the pedals always turn with the wheel (no coasting) IS the primary difference of fixie versus single speed.
These simplifications provides both lowest weight and minimum maintenance.
My fixie (and others I've known) is so light that I routinely carrying it up to my fourth floor apartment, and I never have to think about shifting or flaky derailleurs.
Intros:
http://en.wikipedia.org/wiki/Fixed_gear
http://en.wikipedia.org/wiki/Single-speed_bicycle
http://www.thechainlink.org/group/fixedgearriders

For me in particular a fixie was a natural step for several more reasons. Coming from many years of urban inline skating I felt physically ready and intimately familiar with direct thrust to ground drive. Further it matches my love of minimalism, and not needing shifters is a perk of living in flatland (glacially scoured Illinois). Also now I have two bikes which is very important as a spare for friends. Finally but very important, fixies have a unique degree of artistic performance potential.

After several weeks of research on the specific subject, and of course years of growing familiarity on the nature of bikes, I was recently exposed to some fixie riders from whom I most clearly perceived some benefits. The purchase followed a quick thread on FaceBook where I finally hammered out the specs with knowing friends.
Gear ratio in particular took some work to find. Eventually I found common front "ring" tooth counts ranged 38,44,48,52; rear ranged 14-20. The math is actually pretty straightforward and forgiving. Going from my own current bike and some feedback, ratios in the 2.6-3.1 range seemed good, capable of both high speeds, and strong headwinds. Lower ratio means easier to pedal but harder for speed. No gears at all would be 1:1.
Primary criteria: gear ratio, handlebar style, brakes, weight, wheels, fenders.
Regular commuters require fenders, true minimalists mount only one or no brakes. Some users may have much higher or lower gear ratios, and use pedal clips and shaped handlebars.
I chose simplest handlebars, front brakes minimum, ratio less than 3, whatever wheels come, lightest affordable, no fenders.

My closest good bike store happened to have a super simple new KHS seemingly targeted to my type, having a rear hub ready for mounting an optional fixed gear. The price was quite reasonable, and shows the brand's awareness of its market.
This KHS is fairly light (about 23 pounds), straight handlebars, extremely smooth front and rear brakes with small grips, no fenders, flat dark green. Mine is medium in a range from S to XL.
Wheels measure 24" inside double walled rims, 28" outside tire 1" wide, over 110psi, labeled Weinmann SP17.

Specs say the stock gears are 44 front and 16 rear with freewheel (ratio 2.75). I had them flip the rear and add a 17 fixed (ratio 2.59).
I also bought a Kryptonite lock and had them install some new bracket they pitched which is exceptionally logical, compact and firm. The shop also put on a bottle holder free.
A day later after some riding I had them install a kickstand.
Two days later I also had them swap out the "gnarly" stock pedals (which could never be ridden barefoot), AND install a more comfortable seat. But ultimately so much shock transfers directly to rider that even the best seat is not dreamy.

http://www.khsbicycles.com/06_urban_soul_09.htm

First impression: This is a VERY different experience from common bikes having a coaster mechanism. It's intensely striking me as an instrument, as opposed to just a vehicle. Much like the skating experience, the immediacy of control is simply fantastic, but with a better range of speeds at far less energy. As a skater I must admit, the greater convenience due to bike infrastructure soundly trumps. Compared to either bikes or skates however, it has new learned physical skills.

Second week impressions: I continue deeply loving this bike. Have shed the bottle holder (was catching my pants), replaced the big plastic cheap stock mounted reflectors with reflective tapes, and added tiny head and taillights.
Also got THREE FLATS in two days. Literally. First was pinch flat from hitting too high a curb at too fast a speed with tire pressure not high. Patched those but felt another. Patched that (possibly not well enough), went flat again soon. Replaced tube (unknown quality), was flat the next day. Took the wheel back and had them install a "stop flat" liner and new tube and check all.
That answers my question about how much abuse they can take. The answer is some. 700C tires are reasonably durable, but for best results treat the bike just a little tenderly, get a liner, watch the pressure, and carry a spare tube.
The gear ratio (44:17 = 2.59) is perfect. I can comfortably range from fastest (can't pedal faster than 25mph) to near stationary without feet ever leaving pedals. An impression I intensely try to convey, is that it's a peculiarly unique feel, very confusing on first try. The extension-of-self quality has few equals. I have yet to work on going backwards.
No photo yet, but by nature there's not much to see. Now thinking about names. Regardless of its crossbar design, I need this one to be female. Strong, sturdy, to be taken seriously, and female. Potential name: KHS + Fixie + Kickstand + Komedy + female = Kixie.

Third month:
I continue deeply loving this bike.
Some weeks back I shed the kickstand, "primarily out of respect for fixie tradition" but also because it was the most obvious expendable weight. The inconvenience quickly became none, as I simply changed habits.
I also shed the bottle holder and pump mount, since both have other carry options as needed.
I did ADD a great BIKEPUTER. Tiny, full featured and with wireless transducer, under $20 at Target. Even includes backlight, temperature, and fat/cal info. Also added, after some days searching, good head/tail lights. Powerful, yet nearly unnoticeable when idle.
Eventually got a rear flat. Kudos to Performance I happened to be by, who replaced tube plus all work while I waited for about $15! Next day, I had Uptown install a rear liner. Should've done when I had front put in, but real culprit was low pressure as usual. I need a good upright pump. I now carry a spare tube and basic tools under seat.
Technical tid-bit, the crank plate bolts need regular tightening. Failure could be catastrophic. Should probably have been designed with locking nuts or reverse thread. But serious cyclists do routine pre-flight checks.

Recently, I finally shed the back brake. Again partly out of fixie tradition, but also because it was ultimately irreconcilably incongruous. I have consciously traded some small degree of safety, for aesthetic purity. This has taken some careful learning about quick stopping procedures and weight shifting. I also replaced the big plastic reflectors with "LightWeights" on spokes. This is probably as light as she's ever gonna get.

Sometimes I wish the handlebar was higher, but sometimes I wish it was dropped; sometimes I wish the gear was bigger for speed, but sometimes smaller for wind; sometimes I wish it was lighter, but sometimes I'm glad it's steel. Bottom line, it's a near perfect solution for my mix of needs.

Given the nixing of kickstand, she's earned a permanent name (and humorous followup): Knixie ("both K's are silent")

Photo at top is Knixie on beautiful rack outside Walgreens on Ridge, before most recent mods. This is a great joke, because no bike design is more similar than fixies to the ungeared Velocipede on which the rack is modeled.

One year later (purchased on July 25th 2009) photo below, resting on the water fountain on the lakefront path at Fullerton: