I'm changing from 700c to 650c wheels this season and trying to figure out my new gearing. For my riding style and terrain, I was very happy with my 53/39, 12-23 setup for 700c wheels. The only change I am making is that I want to have a slightly higher top gear. Using a gear calculator to determine gear inches I've found that a 42 front chainring with a 11-23 rear cassette will give me nearly the same gearing I had on the 700c with the small ring. Now I'm trying to pick between a 54t or 55t large chainring. The 54 matched with the 11 tooth rear yields 120 gear inches and the 55/11 yields 122.3. My old setup 53/12 yielded 116.1 gear inches. So do I go with the 54 or 55? How big of difference is there going to be with a 1 tooth difference on the front chainring? I'm tempted to go with the 54 for cadence, but worried about gearing out on big descents (but how much pedalling do you do above 40mph anyway). Any thoughts?
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