You running standard or with Wolftooth? I reckon the 42T will fit but I wonder if I'll need that low for TCR? TransP was up and then down the whole way whereas TCR will have long, flat sections where big jumps in gears will get annoying again.
I'm not arsed about gaps between gears - unless I'm trying to hang on to a bunch or do a TT. For riding on my own, I can spin up or down enough to manage fine.
For the 11-42 vs 11-40 there is an extra 1 tooth gap between the two bottom end pairs, rest of the cassette is the same.
You running standard or with Wolftooth? I reckon the 42T will fit but I wonder if I'll need that low for TCR? TransP was up and then down the whole way whereas TCR will have long, flat sections where big jumps in gears will get annoying again.