i just bought an iro mark v pro i got it on thursday, it was working perfectly for three days includning a ride. today i get on to go meet for another ride and when i pedal really hard something gives and the pedals slip the same thing happens when i skid. im thinking its either the lock ring and cog or crank but i dotn know enough about either to know how to fix it. any suggestions?

What kind of cog is it?

Some of the Surly cogs (I think they've since fixed the problem, so probably just the older ones.) were a little too narrow and would leave a thread or two worth of space between the cog and the lockring. I had the same problem. I installed a small spacer (a bottom bracket spacer will fit) between the cog and lockring and haven't had the problem since.

-Trevor

do some hard sprints to get the cog tightened on really well and then use brakes or your feet to stop and go to the LBS and get them to really crank down the lockring (if you don't have a lockring remover). If this doesn't work maybe trevor's advice will.

did u assemble it yourself? maybe email tony and ask him.

Get that cog and lockring as tight as possible before you strip some threads.
Are you riding with no handbrakes?

i have a bianchi pista that i got hit by a car on and the rear end is slightly out causing my chain ring to have a very small clearance on the chainstay. whenever i accelerate really hard or am skidding, sometimes the chainring and/or chainstays flex to the point that i grind the chainring against the stay.... hows your clearance on your bike??

Pretty common. If it is an IRO build it likely has a SOMA cog. Your cog got snugged down tighter from pedaling than it is possible to do with a chain whip. Then as a result the lockring is loose. When you brake the cog slips until it meets the lockring. When you pedal hard it tightens again. This happened to me on my IRO and I knew what it was. I pedaled the cog on as tight as I could and then retightened the lockring with a lockring spanner. It has been fine since. Blue loctite on the lockring also helps. But if you get both the cog tight as possible and then the lockring it should be fine.

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.

Agreed, more or less the exact same thing happened to me with my new wheels from IRO, but with a dura-ace cog and lockring instead of soma stuff. Simply screwing the cog on real tight with pedal pressure then tightening the lockring with a spanner worked fine.