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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 02-17-07, 01:42 PM   #1
Sigurdd50
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Pros/Cons: Chainring sizes? 52? 36? 42? etc

I'm schlepping a single speed back up together with a frame that has been hanging in the rafters...

I want to use what is available in my heaps of stuff... but I'm coming up short of a chainring in the 40-44T size for the size of the crank BCD i have. (the low 40's seem to be the most common combos)

I DO have a 52T chainring as well as a 36T chainring in that size... plus a few cogs that I could work up if I use a cassette type rear wheel

Question: Is it all just gear ratios and mathematics, or are any pros/cons to using a large chainring/cog (say 52T/21T combo) or small chainring (36T/15T combo)

or does someone have a 40-44T chainring (5 bolt, 65MM BCD that they'd like to float to me *grins*?)

thanks for the input

Mark

Last edited by Sigurdd50; 02-17-07 at 02:03 PM.
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Old 02-17-07, 02:04 PM   #2
euphoria
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here's one bit of science: the 52x21 will make you look like a badass
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Old 02-17-07, 02:18 PM   #3
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it just works in ratios, chainring size is a relitive to cog size.
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Old 02-17-07, 03:05 PM   #4
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Issues, in descending order of importance:

1. A 52 might not clear your chainstay at a 42mm chainline, which is pretty much game over. 42 clears for almost any frame, since road double standard is 41mm for the inner. In between, you pretty much just have to try it and see what happens, I have a 48 that clears by like nanotubes, YMMV.

2. 42 lets you use 14t-16t cogs and get reasonable ratios, which are the common track sizes so they're easy to find. This used to be a much bigger issue when dura-ace was the cheapest good cog but they didn't come in over 16t. Now you can get rebadged surlys (rockwerks or something like that) for $20 and they come all the way up to I think 20t. For 52 most people would want a 19t or so, but if you want bigger than a 20 the options are still rather few, plus they cost a little more.

3. 42 is such a common road size you can get rings really cheap

4. All other things being fairly equal, more chain wrap/contact is better than less, so a bigger overall drivetrain can be good.
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Old 02-17-07, 03:38 PM   #5
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bigger drivetrains wear slower.

also, you said singlespeed, but if you're considering fixed and like to skid, don't forget about skid patches.
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Old 02-17-07, 04:55 PM   #6
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Right, I missed the part where this is for SS and not FG. Screw-on SS freewheels don't come lower than 16t (somebody makes a 15t. not sure how well it works), so you might want to go a little bigger than 42t depending on the gearing you want. Plenty of people run 42x16 and like it, though. When you get over 18t a lot of freewheel manufacturers only make even sizes, another concern.

When you say 65mm BCD, are you sure that's what you have? I think you probably have a 110, which measures 65mm center to center for adjoining holes. These chainrings are everywhere, you can get rocket rings in any size for like $15, though after running one for a while I think the salsa or others for around $30 are well worth the upgrade.
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