re-converting my fixie
 

i have an early 80s trek road bike that I converted to a fixed gear a few years ago. Now I want to convert it back to a geared road bike. I have all of the original components except for the chain rings. The crank is an SR double 130 BCD 5 bolt. It currently has a small track chain ring attached (42 teeth I think).

Question- Am I ok to purchase just an outer chain ring (say 52 teeth) and install with the current setup? Or should I purchase both new inner and outer chain chain rings? Is there anything I should be aware of besides the 130BCD and number of bolts?

Thanks for any help...

You should make sure the 'track' chainring you have isn't 1/8" thick. If it is, the teeth may be too wide for a standard road chain. If it is 3/32" wide, you should be fine with just adding a big ring. There are exceptions of course; older 3/32" chainrings may still be too wide for modern 10 speed chains. Since you say its a conversion, I am assuming it's not a modern 10speed (10 cogs in back) drivetrain.

Besides that, if it is a true track ring that you have, the countersinking may be on the wrong side of the ring. You may want to flip the small ring around so the countersinking is facing the frame rather than facing the crank. Even if you don't, you probably won't run into any trouble.

Last issue that may arise: If you got new shorter chainring bolts when you went to a single ring up front, you may need to either use the old, longer bolts if you still have them, or buy some proper length bolts for a double rather than single ring setup.

And go with a 48!

If you intend to go back to 6s-7s, not much else you need to be aware of. If you do go to a more modern drivetrain, the newer chainrings are ramped and pinned to improve shifting. Sheldon has a good explanation of why this is on his web site .

Thanks for all of the great info. I am thinking about buying a salsa chain ring as a replacement. Why should I go 48? I have a 52 on my cross bike and am comfortable with it. Does anyone else think this is the way to go? One concern I have is that my small ring in pretty big... like a 42. Thanks again!

I just think the older bikes were typically geared a bit high. If you can pull it, more power to you.

almost there...
 

I am having a difficult time measuring the width of the chain ring. Is there an easy way to tell?

I just de-converted this one. I replaced the bottom bracket and crankset, but decided to keep the single chainring for a while to see how I like it.
http://inlinethumb34.webshots.com/27...600x600Q85.jpg
http://inlinethumb47.webshots.com/42...600x600Q85.jpg

If the teeth on the chainring are 3mm wide, then it's only to be used with a 1/8" single-speed chain. If they're 2mm wide, then you can use a 3/32" multi-speed chain.

If it's a track chainring, then 3/32 chain won't go on all the way over the teeth. The rollers won't bottom out between the teeth.