Sprocket Chainring

What are the differences between sprocket/chainring combinations?

I'm a fixed gear riding courier based in London.

I'm just wondering what the advantages and disadvantages are of having a smaller / larger combination are?

For example: both 36:12 and 48:16 equal 81 gear inches, so what differences are there?

I'm bearing in mind things like wear (obviously the larger is better for that one) but also if it effects anything like tricks (wheelies, fakies), ease of climbing, etc...

Please help me out!

If you're running the same ratio, but with different gears, it just comes down to two main differences in the forces put on the chain/components:

Larger rings/sprockets will generally increase the longevity of your chain and sprockets, and reduce chain tension a bit. The caveat is that you may need a higher BB to compensate for the reduced clearance of the larger chain ring up front.

Obviously, the opposite holds true for smaller ring/sprocket combos.

As far as tricks go, generally I see people with smaller chain rings and smaller ratios doing lots of tricks - I think they take the que from BMX in this regard, since you can more easily torque a small ring up front an pop wheelies. In my experience, it's more responsive - Though, you will have more movement required (fraction of a pedal stroke) when doing track stands and such.

If your main use is for your courier duties I'd go 48:16 on a higher BB frame. You can also run a smaller cog on a flip-flop hub if you ever need to cover some ground faster. If you're doing tricks, consider 36:14 or similar. Really it's a matter of personal opinion though - If you've got the $$, get 2-3 fixies if you're really into them.

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