Chain slip

Check your chain line.

I believe I have been but please elaborate in case I'm missing something obvious.

I believe I have been but please elaborate in case I'm missing something obvious.

Take a look at the FAQ, up in the upper right corner of the page. There's a discussion of this and a link to info on how to check it. Good stuff.

My guesses would be a loose chain, a chain with a nearly broken or a stiff link, chainline (viewed from the back wheel the cogs front and back should be as close inline as possible), worn chain and/or cogs, bent or missing teeth, or a failing freewheel. Best results are using SS specific cogs and chainrings with no shifting ramps or "half teeth" (I don't know the correct terminology) to aid shifting, although I have used them with success if the chainline is perfect. Singlespeeding puts a lot of stress on the drivetrain, minor flaws will rear their ugly heads sooner than geared bikes. If you're riding a converted bike with a chain tensioner like a surly singulator the spring tension may be too low.

Some chains don't like ss free wheels...

Your chain size should match the cog size.

The chain that fills the cog should perfectly fit, less gap is better.

maybe it's the hub?

its elves.... definitely elves....


or your chain line isn't correct like everyone else said....

either one... both...

I agree with matching your chain to your chainrings/cog. I had this same issue when I built up my One9. I put on a bmx style singlespeed chain thinking they it was stronger than the skinny 9 speed chains. Kept dropping the chain when I would attack the hills. My chaninline was good, so I switched to a 9 speed chain and haven't dropped the chain in the two years since the change. Also, I have since learned that the 9 speed chains are as strong as the bmx style chains. Hope this helps.

Blackspire Mono Veloce chainring with Surly cog.

I had real chain-drop issues with my SS Rockhopper (sliders), but no issues with my SS Stumpjumper. The main problem on the RH was keeping chain tension.

Make sure all the parts (chain cog and chainring) have the same amount of wear. an old chain with a new chainring or vise versa has been know to cause issues.

Maybe somebody put a banana in there..

chain

used to have same issues, even w good chainline. switched to KMC kool chain and it helped a good bit. but start with the chainline/correct chain size.

Make sure you have the right chain size first, I have a BMX chain and it works great (they ARE meant for SS set up), and insure correct chainline. Then make sure it is as short as possible, mine slipped when I first built it, I took one link out (made the tensioner a tight fit) and it works awesome now.

Eat a Bologna sandwich and wash your hair with vinegar.
After that go to the bike shop and get some one else's eyes to look at it.

How about a photo of your setup?. It does sound like a chain mismatch, but one has to go out of their way to get an 1/8" chainring or freewheel (even Surly has gone to a thinner chainring to accommodate a 9 speed chain); so I'm guessing a bent chainring tooth and a chain that's probably too tight.

As others have said either:

1. mismatched chain and cog, e.g. 3/32 cog with a 1/2" x 1/8" chain
2. chain line out of whack

Check the chain line, I thought mine was dialed but had it looked at at the bike shop and it was way off ;( .