My wife just became the proud owner of a very lightly used 2008 Trek 7.6fx. This model has the Shimano M443 triple crankshaft and a 9 speed rear sprocket with "105" rear derailleur. Because 90% of our riding is done in pancake-flat terrain and the other 10% is gently rolling, she obviously has no use for the triple up front and we would like to change it out to a single - the existing 48 big ring would be fine.
Question is, what is the best way to do this and maintain the best chain-line? Is it:
(a) Pull the crank, remove the two smaller chainwheels, and leave the 48 in the outermost position
(b) Pull the crank, remove all of the chainwheels and put the 48 back on where the middle ring was
(c) Pull the crank and replace it with a dedicated single chainwheel crank
(d) Something else
Logic tells me that (b) should give me a completely acceptable outcome, but I tried this same process with a triple Sugino on an old Cannondale H200 with an XT rear derailleur, and the chain kept juimping after a couple of miles for reasons I could never quite figure out, but assumed had something to do with the chain-line (what else could it be?).
Don't want to have this happen to my wife's bike - I can shrug it off when it happens to me; not so when it happens to her.
Thanks in advance - all advice appreciated.
P.S. - Solved the Cannondale issue by turning it into a single speed - great around town bike!