Originally Posted by
dstrong
I've always used the large/large method...not running it through the derailleur and adding a few links before cutting.
Just so I'm clear, the small/small DOES run through the derailleur and you take out enough links so that the derailleur has tension, right?
Yes. As long as the lower end of the cage moves forward when the ends of the chain are brought together and the chain doesn't rub either on itself or an upper chain guide on the cage, then the chain is short enough.
When using the big/big method, two links (1 inch) are added, unless the ends that come together are the same. In that case, add three links to get one pair of inner plates and one pair of outer plates to join.
Depending on the chain stay length and the chainring/cog combination being used, there are times when an extra inch of chain is needed, just to gain 1/4 inch for one tooth of additional capacity. That's also why some combinations that exceed the manufacturer's maximum will work on some frames and not others. If you happen to have the perfect chainstay length it will work. Some other frame could have 3T less wrap capacity.