I recently purchased a Fantom Cross Uno to use as a winter commuter/around town beater. It came with a freewheel which is fun for tooling around and hopping curbs but the novelty is wearing off and I'm gonna set it up as a fixed gear soon. I'm thinking about getting this one https://www.amazon.com/Avenir-Fixed-G...r+cog+15+tooth The last cog I had was the 17 tooth version and I used it for two years through every season. I estimate that it had well over 2000 miles on it before the old bike got stolen, and that includes grinding on lots of salt and sand. The last time I examined it there were obvious signs of wear but not nearly as bad as I expected for the amount of abuse it got.

What makes something like a Dura Ace, All City, or Surly cog more than twice the price of the one I linked? Do they honestly hold up that much better or is it about branding? Weight is not a concern for me. If it's worth the extra money for the extended lifespan I'm all for spending a bit more but I just don't have the first hand experience with more expensive cogs to justify the difference.

Ooh, this is going to be good.

I have a feeling the answer revolves around material used, manufacturing tolerances and surface finish, but with BFSSFG you never know what you'll get (cat .gifs).

I've had both dirt cheap and good quality cogs.

I've heard expensive cogs make less noise. From high school physics I can guess that less noise is a result of less friction and slack in machining which would theoretically mean you have less energy lost in the drivetrain. Probably 0 possibility of measuring a performance change let alone feeling one when you're riding.

As far as holding up to wear goes, if your avenir lasted 2 years a fancy cog like the EAI gold medal ($89.00) would have to last over 25 years to have paid for itself in cheap cogs.

Bottom line: If money's burning a hole in your pocket and you've got nothing else to do, buy a fancy cog. If not, you'll probably be perfectly happy with another cheaper one.

They pretty much hit the nail on the head. I wouldn't go super cheapo unless I had to. Something like the EAI gold is unreasonable, but a $20 formula or $10 miche cog is where I would draw the line.

The main difference between a dirt cheap cog, and anything else is the dirt cheap cogs are stamped out of sheet metal rather than forged. A forged cog is stronger, has a better tooth profile and rounder. A really nice forged cog is round and has a better tooth profile than an average forged cog. If you need anything 16 or under get a Dura Ace cog, over that I am not the guy to ask.

EAI Deluxe

This. ^^^

The threads on the cheap stamped cogs can also be sketchy and can damage the hub threads in the case of a poor fit. I've never bothered with the fancy-pants EAI Deluxe or Phil cogs; those black oxide treated Dura-Ace cogs work fine and give a better bang for your buck.

So in the end, pretty much if you need something 16t or under, go with DA.

Need something above that, go with EAI deluxe or the Soma cogs work perfectly well also.

Tooth profile plays a part as well. I'm a fan of Surly's style of deep, square teeth. They can be more forgiving of less-than-perfect chainline.

+1 my surly has not worn a bit while I've had to replace my chain a few times as it stretch to the point of ruining chainring