Singlespeed & Fixed Gear - Rough drivetrain

A couple of weeks ago I converted an old Centurion Elite RS to fixed gear to try something different over the winter. I've put about 75 mi on it now. Is it just a fixed gear thing to feel some drivetrain "roughness" through the pedals? My road bike is smooth as glass. The bottom bracket, chainring, chain, and cog are new. I overhauled the rear hub and everything looked OK. The chainline is only about 1mm off and it's adjusted to have about 1/2" slack. Thanks.

Worn chainring/cog?

roughness through the pedals? what does that mean?

maybe you need to overhaul your pedals.

Do you mean it's a roughness when you really mash on the pedals? If so, I have the same thing on my old Centurion. Welcome to old frames. They're not that stiff.

A lot of conversions are done with crappy parts. If you are using a $10 chain, for example, nothing in the world is going to make the bike feel good. Same goes for some of the bargain basement cogs floating around out there. And if you simply reused the old chainring that was on the bike, chances are it isn't meshing with the new chain very well -- unless you're using the old chain too, which would be another clue.

Oh, and frame stiffness really doesn't have anything to do with it.

Thanks for your responses. The chain is a new PC58, the cog is a new Rockwerks and the chainring is the old one but is not worn. Maybe I'm expecting too much from an older bike.

Age has nothing to do with it. I've ridden bikes from the 1930s that were perfectly smooth and quiet.

There are only a few things that you need for a smooth drivetrain: good chainline, and good quality cogs, rings, and chains. Nothing else really matters, unless something is seriously non-concentric.

The bottom line is that you're using a low quality cog and a medium quality chain. Those would be the first places I'd look.

Do you mean it's a roughness when you really mash on the pedals? If so, I have the same thing on my old Centurion. Welcome to old frames. They're not that stiff.

something's wrong with your bike—my old centurion is nice and smooth. no roughness. plenty stiff.

Your new cog and chain are fine. They may need a little time to break in, but I doubt that is the main source of your problem. It could be your chainring. I've had similar "roughness" problems with a cheap salsa chainring, which I finally swapped out for a good Sugino Messenger ring, and it totally smoothed out the DT.

Your new cog and chainring are fine. They may need a little time to break in, but I doubt that is the main source of your problem. It could be your chainring. I've had similar "roughness" problems with a cheap salsa chainring, which I finally swapped out for a good Sugino Messenger ring, and it totally smoothed out the DT.

...uh

Drivetrain parts can take some miles before they play well with each other.