Originally Posted by
Retro Grouch
How badly are the crank arms boogered?
If they're not too bad you might be able to insert the correct pedal in backwards to clean out the threads.
Average or better bike shops will have a die to chase the threads but they'll probably suggest replacing the crankset.
+1 before simply replacing these cranks, I'd take a good shot at salvaging them.
Sometimes the pedal thread is long enough so that by threading it from the inside (towards the frame) out it'll straighten the bad outer threads as it reaches them. If the pedals don't thread deep enough go to LBS, and have them do the same with a pedal tap. BTW- watch the mechanic and be sure he goes from inside (good thread) to outside where the bad thread is. I say this because too LBS mechanics try saving bad cranks from the outside, where the pap is just as likely to pick and take the lead from the damaged thread.
Also, if it's the right crank, you might find an inexpensive pedal tap at the auto store. 9/16x20 is a common spark plug thread, unfortunately they don't also make spark plugs with LH threading.