final thoughts after upgrading my mark v's drivetrain
 

Today, I finally had a chance to put the finishing touches on my Mark V's new drivetrain ( Pictures and details here ) After removing the 1mm bb spacer, my chainline was as close to perfect as I can tell and quiet to boot.

After 10 odd miles of riding, I was thoroughly impressed with the setup. My new 49/18 gear ratio makes spinning, hills and starts a lot easier, although moving a little less per revolution is going to take some getting used to. It's smooth, responsive and stiff, and for not a terrible amount of money.

I'm sort of glad that I opted to go with the sealed cartridge bb, instead of the sugino 75, since there was a decent amount of brown grimey water that came out after the original bb was removed. I also would estimate that my chainline is off by less than a mm, so a 109 wouldn't make a world of difference.

I'd also like to note that the threading on the IRO BB might be a little odd. I make absolutely sure that I wasn't stripping the bb, but there's varying amount of resistance when instaling. Perhaps it's the UN-73 bb.

The stock drivetrain on the IRO is the weakest link, especially if you ride it a lot. While a new chainring might do the trick, money spent on an upgraded drivetrain is mone well spent.

+1 I just went through and picked apart my drivetrain to figure out a clicking noise i was having...it turned out to be the chainring although i did replace the BB too, which ended up needing to be returned for non compliance w/ my crank arms...but alas it was that stupid chainring... and im done rambling