London Fixed-gear and Single-speed

I´ve had an idea that I´m going to try tonight, I´ve got good quality cnc sprocket and chainring but i´m having problems getting even chain tension through the full rotation of the cranks. If you look closely at the crank/chainring, you can see that the c/ring isn´t sitting dead centre and there are gaps that vary in size between where the c/ring rests against each of the five arms of the crank.. . .anyway, I reckon that a bit of shimming from a ally can should do the job.

I´ve seen a few threads about this, different ideas have been thrown about but I´ve never seen anyone mention shimming, has anyone tried it?

Never needed to. Do your chainring bolts match the chainring? That is, are they from the same manufacturer?

Yes, both from sugino. There´s always going to be a bit of slack/play (call it what you want) as neither the chainring to the crank, nor the bolts to the crank are a press fit, so I´m not surprised it ain´t perfect. Personally it annoys me a bit, and I reckon I can make it better, we´ll see!

maybe a bent bb?

Have you tried

http://sheldonbrown.com/fixed-conversion.html#tension

Mine's the same. Annoys the shit out of me. Should probably just buy a better one, but when I start thinking like that a whole new bike starts to build itself in my brain.

So go with the flow...

I've just tried the link (it works).
Pretty good advice for centering your chainwheel, to even up the tension through the full revolution of your cranks