Looking to replace your Shimano R9100 inner chainring? Shimano developed a unified (standard and compact gearing use the same interface), 4-arm asymmetric crankset spider design for the 11-speed cranksets. For the Dura-Ace Hollowtech II R9100 crankset, the inner rings are designed, to perform better with new R9100, R9150 front derailleurs, so the ring was offset inboard to the frame by .4mm. In other words, these R9100 replacement rings are not designed for the 9000 Dura-Ace cranksets unless you have updated to the FD-R9100, and ST-R9100/9120/9150/9170 STI levers

In order to withstand daily riding by top level cyclists, as well as the power of the Di2 front derailleur, the R9100 inner chainring is machined from hardened aluminum, then black anodized for max corrosion and wear resistance. The teeth are highly engineered following Shimano's patented shifting integration system for optimal shift efficiency, chain retention, and wear, and designed with matching precision to the Hyperdrive tooth profiling system shared with the outer Hollowglide ring. When selecting a new inner chainring, please remember the inner and outer rings are designed as a system, so a 42T inner ring should be only be paired with the proper 54T outer ring. The other combinations are listed below.