Originally Posted by boots
Yeah, this happened to a friend of mine who just bought a Mercier. Most likely the lockring wasn't tightened enough. Tony's a great guy, and I can't say enough nice things about IRO, but he's not a ISO-9000 shop, you know? He builds his bikes in his garage. Sometimes he overlooks things.
I built the bike from scratch. So no IRO Tony issues here. Actually the cog was initally not tight enough. The pressure of my 180lbs and big legs tightned the cog more than I could with a Park Chain whip. Then the locknut had to be retightened. When you first put a cog on IMO it is best to go out and ride it hard without braking hard or in my case trying to skid. Then retighten the lockring.