Originally Posted by
CEBEP
Does it mean my R&M Birdy Touring can take 56/44 on stock spider and shift normally and not rub anywhere?
Yes, I have been using this setup for a couple of years without problem. Derailleur capacity is a huge consideration. Per Shimano spec I should be using a medium GS RD. I have been using a short SS R8000 RD with this setup and I never do cross chaining in either way. The SS RD will not allow me to do cross chain anyway. This is something I had to pay close attention to.
As long as your Birdy uses standard external BB with a 2mm spacer on the drive side. It is safe to do it with double chainrings.
I was using a Chris King Headset. Last few weeks I switched back to stock Driveline BB and 53/39 setup. Still working fine without any problem. Shifting is even better and faster than the old 56/44 setup.
The combination on the size of large front chainring and largest cassette cog size is another story. We can't do 56T-34T combo. In a cross chain state the chain will rub the bottom side of the rear fork. I can't remember about 53-34T combo but 52-34T works without rubbing.