newbugdriver

I have a 2009 Trek 7100. I had a bent rim, that I had my LBS replace with a double walled rim and upgraded to a 7 speed cassette (bike originally had a 7 speed freewheel). They also had to add a spacer since the rim was setup for a 8 speed cassette. I was told my derailers may need adjustment (which they did). Everything is perfect, except for whenever I am on the two smallest sprokets on the rear cassette. It seems that when I peddle, it doesn't seem as smooth as the other sprokets and I feel a very slight vibration. Any ideas what might cause this on these two sprokets?

Thanks.

Mr. Beanz

At times ,after replacing my wheel, it will seem that all is fine and dandy with the adjustment. Can be different under load. I will put mine on a stand or trainer then pedal by hand then fine tune the rear derailleur barrel til the noise or roughness goes away. Small movements of the barrel (1/16 turns)

Shop does adjustments on the stand but doesn't always test underload or on the road so really, only you know when it acts up! It may seem fine when you leave the shop but not exactly right till roadtested.

BUT keep in mind, like me, my favorite most used cogs get more abuse and tend to run a little rougher than the not nearly used cogs. If it's a big problem, new cog and chain is the answer.