2x9 ala PVD
From Pvdwiki
Narrow Range Front Gearing
The Cassette
The Front Derailure
Chainline
The Ultegra 10 speed Triple cranks configured as a twin gear as I have done produces a chainline of 43.5mm. This is pretty bad. It brings the front derailure very close to the rear tire. Adding an additional 2.5mm spacer brings the line out to 46mm. Any more than this is very difficult to acheive.