Was thinking of ordering some time trial chain rings for my race bike (55/42). Just wondering whether you always get a tt small ring if you’re going with the tt large ring? May sound a little strange but the online shop seemed to advise that the std ring was now available to go with the 55 tt ring. Wondered why you would not have two pure tt rings and whether it defeats the purpose of the concept if one is tt and one is std. I don’t know enough about it to question it so was hoping some of you guys could help out? Is the smaller ring protected by the larger tt ring so the difference is not as severe or should you always go both tt or both std?
Whew where to start.
Regarding the “matched” set of chainrings, many of the TT rings share the solid design of both the inner and outer, but more importantly they are timed to shift together, allowing the chain to remain under constant tension and length while moving from one ring to the other. You can certainly run a non-matched ring and the aero difference would be infintesimal, but the shift quality may not. My TT bike is set up with a standard inner ring, I use a 39t because I race where it is flat and only use the inner for warming up/down. The courses that you’d need both rings for may benefit from them being matched.
Another reason is that the front derailleur capacity for Shimano is 15 teeth. That means that the maximum difference between the teeth should be 15 teeth or less. Campagnolo has a 14t max. difference.
Don’t do it to be aero, do it for maximum shifting performance.
