Originally Posted by jur
I suppose you are referring to the tension set up by the read derailer? This tension is negligible compared to the tension on the top part of the chain that is under load as you pedal - that's the one that buggers chains and cogs.
I need to know why Sheldon indicates that it is not OK to shift the front der. first, from the big to middle chainring - before shifting down on the rear cogs. That is my ONLY question.
If I am in the big front and small rear, why is not OK to shift to middle front without touching my rear??? My chainline is still fine, and the tension is fine. Sheldon seems to indicate that this is a no-no and we should be shifting down on the back cogs before switching the front chainring. What is wrong with going from big front / small rear to middle front / small rear using only the front derailleur?