Originally Posted by
mrtuttle04
Thanks everyone for the imput. The primary reason for replacing the crank is the middle chainring is worn and must be replaced, along with the chain. I realize I can just replace just the chain ring but replacing the entire crank gives me the opportunity to go to a longer crank arm.
The reaon I am thinking about goint to a single speed crank is: 1) the derailer needs replacing but I do not want to sink a lot of money into an inexpensive bike , 2) I ride mostly level ground and have little need to use the high or low gear.
OK. The key to this project is going to be the chain line. You'll want your single chainring to line up with the middle of your cassette. If your middle chainring lines up with the middle of your cassette now (usually the case) measure in millimeters from your existing chainring to the middle of your seat tube. That's the chainline you're shooting for. When you buy your crankset, you'll likely need to get a new bottom bracket too to get the chainline to match. Also, my rule of thumb is to always pair a new fresh chain with new sprockets.
So crank & chainring, bottom bracket and new chain. The cost is creeping up.