Hey Scrod,

Recently my IRO Mark V started to click once every pedal stroke when back pedaling or under load going uphill for example. (I didn't use 'mash' cuz I'm not very fast).

I tightened up everything I can think of including a new 46T chainring but I can't isolate this click.

The pedal stroke still feels smooth but I want to isolate this click so that it doesn't turn into a bigger problem.

I bought this bike used so I'm not sure of all the components but this is what I know:
1) Sugino RD5000 crank = 170mm
2) Sylvan Track pedals (newish, bought these from you last Fall 2011)
3) Retrogression V straps (new, you just shipped me new ones)
4) What looks like a Dura Ace track cog and lock ring
5) Generic 3/32 chain
6) Bottom Bracket - don't know

When I first got this bike, everything was silky smooth, but I've been using this as my daily commuter in San Francisco since last November 2011, 12 miles round trip daily. I haven't dropped it at speed, just dufus 0 mph stuff at stop signs.

Thanks for any insight