Originally Posted by
CCrew
Main reason was actually marketing. 27 being the biggest Shimano made when the spec was published. If you went out and bought a 28 SRAM it gave them an exit from standing behind it..
Irrelevant. We're discussing why that figure is not a 'hard' limit and why it may vary from bike to bike. Even with the exact same cogset + rear derailleur installed.
http://www.bbinstitute.com/dl/dx_demo_chapter_32.pdf
Refer to page 32-19