Singlespeed & Fixed Gear - 52t or 40t chainring?

I'm in the process of converting my World Sport to a single speed, and want to utilize as many of the original parts as possible. The stock chainrings are 52T and 40T. Would there be any pros and cons to going with, for example, a 52/20 vs a 40/16? The gearing would be very similar (2.6 vs 2.5 ratio), and aside from aesthetics, is there any functional difference I'm overlooking? I'm new to the SS/FG thing, so I guess I'm looking for personal experience here. The bike will be used for a 5mi commute and longer weekend rides.

If you use the 40/16 setup you'll have less chain but the sprockets will wear out quicker because they are smaller. Otherwise there is no difference, a ratio is a ratio. Of course, if you are leaving all the existing parts in place, one setup may give you a better chainline than the other.

http://sheldonbrown.com/fixed.html#bigsmall

Either a 40 or 52 will probably be fine. But since it's a World Sport, I'm guessing it has non-removable chainrings. If that's the case, go with the 40 because if you use the 52 you'll have to dish your wheel a lot. If you use the 40, the dishing will be minor, and might not require any change.

The chainrings are removable, and I will remove whichever one I don't use. Sounds like the 52 is the way to go, now I just need to decide what size rear cog to use. Thanks for the quick replies.

if you will be removing the chainrings and can fiddle with the rear cassette, and of course if the roads and terrain will allow it, why not use the 52/16 gear ratio?

this will give you better speed on the flats if your area has more of those and will make it less difficult to go down hills (as you wont be spinning like a food processor)

just a thought...

anyway, if your area has many hills then disregard my comment of course and stick to the 52/20 as has already been mentioned it will reduce the wear on your cog and chainring due to the larger number of teeth

Go with what is most comfortable.

on my commuter bike i have 44/17.

Its really nice(:

And i can spin at a pretty good rate so on the way home i take this long hill in LA joy(:

http://sheldonbrown.com/fixed.html#bigsmall

Either a 40 or 52 will probably be fine. But since it's a World Sport, I'm guessing it has non-removable chainrings. If that's the case, go with the 40 because if you use the 52 you'll have to dish your wheel a lot. If you use the 40, the dishing will be minor, and might not require any change.

How is dishing the rear wheel going to help? All that will do is provide a strange alignment in the frame for the rim. The hub will still be in the same position.

I suppose I should've explained that better. If you use the outside position on a double to do a conversion, chances are when you thread on a freewheel the chainline will be way off.

To get a straight chainline, you'll have to mess with the BB/crankset or re-arrange the spacers on the hub. By moving the hub over, the wheel will have to be re-dished so that it's still centered in the frame.

I suppose I should've explained that better. If you use the outside position on a double to do a conversion, chances are when you thread on a freewheel the chainline will be way off.

To get a straight chainline, you'll have to mess with the BB/crankset or re-arrange the spacers on the hub. By moving the hub over, the wheel will have to be re-dished so that it's still centered in the frame.

That does work, but it wouldn't be my first choice in doing unless the chainline is really out of whack.

Easier to swap bottom brackets or in the case it's a looseball with a replaceable spindle, then simply swap out the spindle for a shorter one and use the inner position on the crankset if it is still a tad off.

Was lucky when I originally converted my 930 into a SS, with the wheel it came with I had a good chainline from the get go. Have a fixed setup on it now(The stock rear wheel from my Pista, which I still had) and kept the same chainline.

if you will be removing the chainrings and can fiddle with the rear cassette, and of course if the roads and terrain will allow it, why not use the 52/16 gear ratio?

this will give you better speed on the flats if your area has more of those and will make it less difficult to go down hills (as you wont be spinning like a food processor)

just a thought...

anyway, if your area has many hills then disregard my comment of course and stick to the 52/20 as has already been mentioned it will reduce the wear on your cog and chainring due to the larger number of teeth

less work, more often = more work, less often

think about how this relates to knees.

I did the same exact thing with the same bike. I ran the 40t chainring with a 16t cog and it was ok, its a really low gearing though and you can't really go all that fast. With the stock crankset and bottom bracket you will have a really bad chain line, so be prepared to get a new bottom bracket. I run a 46x16 ratio now and I think its perfect for where I ride, which is very hilly.

I have an '80 world sport conversion with a 45 chainring mounted on the inside of the stock crank. I'm running a 14 tooth cog, which is a nice ratio for me. It's mostly flat here, but the pinellas trail has some steep overpasses which I can usually climb without standing.

One nice thing about a higher ratio is that it will make your legs stronger.

52t might not fit on inside of the spider due to chainstay clearance... Try it out.

I live in a pretty flat area near the beach, but I also don't want to be hard on my knees with too steep of a gearing. I haven't set up a SS bike before so this is new to me. It sounds like the 44/17 is a pretty good compromise and is more commonly used, I might try that to start out with and adjust from there if needed. Thanks for the input everyone.