high grade: (ultegra or DA)
shifters, crankset
mid grade: (105 or ultegra)
rear derailleur, brake pads, cassette, chain
low grade: (105 or less)
front derailleur, brake calipers
This is just for functionality. Weight savings are a different matter.
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Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --
the tiniest sprinter