Is it brand new philjay? It's normal that the cog will tighten slightly when you start using it so you just need to tighten the lockring. This requires a lock ring tool such as this;
@andyp started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
Is it brand new philjay? It's normal that the cog will tighten slightly when you start using it so you just need to tighten the lockring. This requires a lock ring tool such as this;