Originally Posted by
mangpress
how many miles has the chain had?
how old are your tyres?
how old is the bb?
vertical or horizontal dropouts?
hows your tension?
Are you joking or are you just a moron? None of this has anything to do with a cog slipping.
To the OP, you should grease the living hell out of the threads, run the cog on as tight as you can, pound up a nice long hill with a lockring wrench in your back pocket, then get off of your bike without any resistance and tighten that lockring up really good.