prathmann

And you clearly missed mine. The advice given before was that using the small-small method is *always* the safe way to go - and this was made without any qualifications. That's fine *as long as* the person using it is sure that the rear derailleur has sufficient wrap capacity for the chain rings and cogs that will be used.

Someone reading the previous advice that this method is always safe and therefore using it on a bike where there is insufficient wrap capacity could be in for a very unpleasant surprise if there's an attempt to shift into the large-large combination.

My advice was not to deliberately design a drive train with insufficient wrap capacity, but that one should be sure it is sufficient before relying on the small-small method of chain sizing.

I'd note that this is consistent with Sheldon Brown's advice in:
http://sheldonbrown.com/derailer-adjustment.html#chain
"If the chain is too short, it will be at risk for jamming and possibly ruining the rear derailer if you accidentally shift into the large-large combination. Never run with a chain that is too short, except in an emergency.
If the chain is too long, it will hang slack in the small-small combinations. You should never use those combinations anyway, so this is not a serious problem. If you exceed the recommended gear range for a particular rear derailer, you may have to accept droop in these gears.
The best technique for setting chain length is to thread the chain onto the large/large combination ..."

Of course if one will be using a variety of cassettes then the large-large method needs to be applied with the cassette having the largest cog.