Apologies for adding to this thread if it is past it's sell by date, but I have only just returned from enjoying a two month "holiday" from posting and so was unable to contribute earlier.
So here goes; From my experience as a cycle courier in Central London, on and off for 10 years, I would add this as my tuppence worth:
Go fixed. Do not, I repeat, DO NOT ride a single speed!. Apologies to whoever recommended doing so above, but single speed bikes for the road are the single biggest waste of money and the most utterly redundant invention you could ever hope to find. Instead, send your money to me and in return I will give you the following brilliant piece of advice:
Ride your geared road bike. And DON'T CHANGE GEAR. There. Saved you buying a new bike for no reason
and looking like a poser. Because there is only one thing worse than
being a poser....and that is
looking like a poser! Trust me, I have posed with the best of them, I know.
Fixed information, in my, as always, humble opinion, hope it helps:
1. Crank lengths. Don't ride anything longer than 165. Otherwise you run the risk of foot strike on the road when you are cornering tightly, and a very nasty spill as a result. Looks funny on youtube, but hurts like F*ck! You also end up kicking your front wheel every time you turn your handlebars further than 45%, unless you have feet the size of a hobbit. Again can be dangerous/ cause for ridicule.
2. Don't run even gears. (i.e 48X16, 48X18 etc.). You will go through rear tyres like a hXXker goes through panties, especially if you are skidding too. (Much like the aforementioned hXXker)
3. Don't let yourself be dragged into any piXXing contest about big gear ratios. To start with err on the small side, and put another larger gear (2 teeth bigger) on the flip side of your hub, to play about with as you get used to riding fixed. I would recommend maybe 48X19 (c.68 inches) to start, unless you have legs like a chicken, and a 17 or 15 on the flip for when you are feeling butch.
4. Only ride a front brake. Seriously. ONLY. NEVER a rear brake. It can take very little effort to lock up the rear wheel on a fixed gear, if you do this and don't know how to control what happens....well just make sure someone is on hand to film it, so I can watch it on youtube and say I told you so.
5. Remember this phrase: Buy cheap buy twice! If you think you are getting a bargain purchasing some pre tensile steel "courier" bike from the interweb for 200 bucks, let me assure you that when you snap the bottom bracket/ cranks/ chain etc etc, you will end up chucking the whole thing away. Most of these cheap pre builds do not use standard thread sizing for bb's/ headsets etc. and are impossible to buy spares for as a result. You are much better off either buying a cheap second hand road frame and building your own fixed gear with a freestyle rear hub, or getting a decent frame from surly, on one, independent fabs etc. etc. or even a good old fuji.
6. Ride spd MTB cleats, or if you want to go old school, toe clips. NOT standard one sided Keo's, shimano Road etc. The only way to ride with Keo's is if your track stands are so immaculate, that you never have to unclip. But the downside is you look like a twXt!
7. Use a comfortable saddle. Padded. Make sure it supports your sit bones and that you aren't balancing your entire body weight through your perineum. You stand out of the saddle less on a fixed gear so therefore run the risk of injuring your best buddies if you don't monitor the situation. Beware the numb cXck! Seriously. Especially if you ride any cobbles.
Ok hope that helps....fixed gear cycling is great training, seriously, it improves your bike handling skills, is less hassle with cleaning and maintaining and generally just great fun. I hope you enjoy it.
But please don't ever call it a "fixie". Not even on your own.
And I didn't even mention Alberto....not once....wow!