Chainring teeth wear out — the inner ring usually goes first on any road bike that sees real climbing miles, since the small ring carries the load whenever the gradient tips up or you're spinning easy on recovery. Shimano's Ultegra FC-6800 inner chainring is the direct factory replacement for the 11-speed 6800-generation cranksets, and it's the right part to grab when shift quality starts getting mushy and the chain starts hunting under load on the small ring.

The three tooth counts each carry a type designation that matches them to a specific outer ring. The 34T is the MA type and pairs with the 50T outer for compact 50/34 gearing. The 36T is the MB type and works with either the 52T mid-compact outer or the 46T cyclocross outer. The 39T is the MD type and pairs with the 53T outer for traditional 53/39 gearing. The letter codes exist because Shimano times the shift ramps and pickup pins on the inner ring to hand the chain off to a specific outer ring — mixing types across pairings will roll, but front shifts get lazy and the chain won't catch cleanly on upshifts under power.

All three rings share the 110mm asymmetric 4-arm bolt pattern that Shimano used across the FC-6800 Ultegra, FC-9000 Dura-Ace, and FC-5800 105 cranksets of that generation. That means an Ultegra 6800 inner ring will bolt onto a 9000 Dura-Ace or 5800 105 crank of the same era if you're willing to live with the color mismatch, which makes this a useful budget replacement path on a 105 build or a way to keep a Dura-Ace crank running when the correct 9000-series inner ring is out of stock.... Read More