Originally Posted by
rivers
On my gravel bike I am running Shimano 105, with an FSA 46/30 crankset. The cassette is an 11-32 with a 105 short cage derailleur. Technically, I’m already exceeding the rear derailleur capacity by 2 teeth. When I’m fully loaded, I don’t really have a low enough gearing for my liking. Over the winter, I want to experiment with lower gearing. If I wanted to put an 11-40 or 11-42 cassette on the back, what are my most cost effective options? ...
Have you actually compared the various gear setups? Try this:
Bicycle Gear Calculator
A 46-30 crank with an 11-36 cassette being shifted by a RD that is within spec for the (or really close, maybe 1-2 teeth beyond the spec'd capacity) will give you a low gear that is ONLY 3 gear inches taller than an 11-42 cassette with a way out of capacity RD hanging from a Wolf Tooth extender that gives poor shifting performance on the smallest 3 or 4 cogs of the cassette. People make it work, I guess because they think ~3 gear inches is worth it. A far easier, and less hassle free, way to get the climbing performance you seek is to run the largest in spec (or close spec) cassette you can, and go up hill more.