So I just completed my first fixie conversion and I have a major problem. My chain keeps slipping on the rear cog and it seems as though it doesn't sync with each tooth. My chain line seems spot on and the tension seems fine. I am running a 40t and 14t cog and this brings about a total noob question, but does it matter what chain ring/cog size you run? Do they need to be a certain ratio so the chain is in sync with the amount of teeth? I don't know if any of this makes sense, but I really want my chain slip issue resolved bc I am super excited about this bike. Thanks a lot for the help.

I'm running the same ratio and it works fine. Some chains can very though, for example I just purchased a sram chain and it doesn't line up with my cog.

Are you sure your cog and lock ring are tight?

That's something I definitely need to check. I basically hand tightened those , since I don't have a tool to tighten the lock ring.

Money says that's your problem then. They should be greased and tightened using a wrench. Take it your local bike shop.

My money is on you have a 3/32 chainring and chain and a 1/8 cog. Just a guess.

Ditto.

^ check both.

please get your cog and lockring properly tightened.

i've ridden mixed 3/32 and 1/8 for years, and never had a problem. it's the cog and lockring for sure. you can't hand tighten that ****. if you want to get it tighter, either google rotafix or find the tallest hill near you and stomp up it with all your might. that will get it pretty tight. DO NOT fool around on it with the cog and lockring loose. you will strip your hub after a while.

+1 and to add to the above post its recommended to give considerable torque to both the cog and lockring. and then ride your bike for a short while and re-torque to insure everything is secure and tight. get the correct tools or LBS.

cool, I will definitely go get it tightened today. Thanks a lot for the help.

also make sure there isn't a tight link in your chain as that could be causing a skipping sensation

It could be that as well, bc I took some links out and did a scheisty job putting it back together and one link seemed a bit stuck. I will pick up a new chain as well.

If one link seems stuck, you can usually fix it without replacing the chain. Here's a good explanation on how to loosen up the link: https://bicycletutor.com/stiff-chain-link/

+1

^^^

-1

You can't use a 3/32 chain on either a 1/8 chainring or cog. Period, end of discussion.

A loose cog wouldn't cause a supposed sync problem, if anything it would allow the cog to mesh properly.

It was definitely the chain size issue. I picked up a 1/8 chain and it works like a champ! Thanks to everyone for the help.