CASSETTE WOES

     My previous post described the switching I did to get my road bike (Roark) ready to race.  Well, after the race I needed to reverse actions to get things back to normal.  In my first book,  Bicycle Journeys with Jerry, I opine that I'm a mechanical klutz and other than keeping the chain lubricated, leave maintenance to the mechanics at Bicycle Sport Shop.  I've progressed since then, but still require help when things get technical.
     It seemed straightforward, take off the two cassettes and put them back on to their regular wheels.  I used the Park chain whip without a problem removed the cassette from the Zipp and cleaned the cogs before remounting them on the Rolf wheels.  The time trial cogs, mounted on the Rolf wheels as an emergency back-up, came off-and-on in one smooth action.  I was rather happy at how easy it was.
      I put the Roark on the rack, spun the cranks and ran the chain up and down the cogs.  Smooth.  Ready to roll.  I put the Felt on the rack, spun the cranks, smooth.  Until I got to the 12 tooth cog (smallest).  Clack, clack, clack.  Dang!  For the next twenty minutes I went over everything.  I saw that the chain rubbed the front derailleur but couldn't understand why that would be since I touched nothing other than installing the wheel back on the bike.  Naturally, I took the wheel off and made sure I hadn't missed a spacer on added one.  All was good with the shifting until I got to the small cog.  Time to go to the experts.
     They are always so helpful and solicitous when I walk in pushing my Felt (they are when I bring in my Roark, too).  I explained the mysterious clacking and was assured they'd be back in a minute with the explanation.  Several minutes went by.  I needed a new bottle of chain lubricant, so purchased that and took it to the car and came back and waited some more.  It took quite a while, but they sleuthed until finding the answer: the cog was bent (out of alignment).   Pook, ding fu!  They also did a little adjusting, so that shifting remained smooth.
     Back home, I removed the wheel, took my magnifying glass and closely examined the cog.  I could see nothing wrong or out of the ordinary.  I put the wheel on the Roark, and got the same clacking result.  It's not that I distrusted the diagnosis, I just wanted to see what I'd missed.  I'm guessing I must have hit it somehow when putting it back on the bike.  Bah! So now I need a new 12 tooth Dura Ace cog.  I sure as heck don't want to purchase a whole new cogset.  I have several options, including using the Ultegra set on the Roark.  But races are just around the corner and I need to make up my mind.