I think most of us are aware of how conservative Shimano tends to be about mixing and matching bits like chainrings. In actual practice however, at worst you tend to get slightly less than optimal shifting.
But for the current, 11-speed generation the current manuals seem emphatic about it. To the point of stating you can break something:
Be sure to use the specified gear tooth combination. If an unspecified gear is used, the chain may enter between the gears, damaging them
I wondered for a long time how the chain might “enter between the rings”. Is there a difference in the distance between them depending on which small ring you use?
But I had the 50/34 crank (combination “MA”) and I wanted 50/36. We all know they don’t make 50/36. But Shimano only recommends the 36 for combination “MB” – 52/36.
So I went ahead and bought the 36 anyway. Fits perfectly. Shifts perfectly. Still scratching my head about this recommendation.
Anyone else mix and match them for 9000 or 6800? Any problems?
http://si.shimano.com/php/download.php?file=pdf/dm/DM-FC0003-03-ENG.pdf