One principal I've always followed is that if you rarely or never use part of your bike something is wrong.
If a cyclist always uses the top of the handlebar and brake hoods and never the drops their handlebars are too low.
If a cyclist never uses the big chain-ring than their bike is geared too high.
Likewise if a cyclist never uses their small chain-ring their bike is geared too low (ok, I never actually saw this but you get the idea).
Back when I raced I noticed that I didn't need as high gears for my beater bike as for my racing bike. On my racing bike I spent about half of my time on the 42 and half on the 52 but on my beater bike I almost never left the small chain-ring. I ordered a 36-48 crank. The 36 gave me lower gears for riding home heavily loaded with groceries and the 48 gave me a large chain-ring I could actually use.
When "compact" cranks came out 25 years later I felt vindicated! Smaller chain-rings; whoda' thought of that?
Speed is relative term. The big chain ring will increase the distance per revolution, it will also decrease the torque. If you turn high RPM's in the smaller chain-ring you can achieve similar speeds.
Let's do an example:
1. Front Chain-ring = 39, rear cog = 14, RPM 105, Speed will be 22.35298295 mph at the roll out (2050 or 80.7") I programmed into my Excel spreadsheet.
2. Front Chain-ring = 53, rear cog = 19, RPM 105, Speed will be Speed will be 22.38314892 mph at the roll out (2050 or 80.7") I programmed into my Excel spreadsheet.
That's pretty darn close. Study your math and gearing. There is nothing to fear.
I try to avoid the big chain ring early in the season and work on keeping my RPM's higher (85 to 110). I'm old and have always allowed my knees and legs time to adapt, (4 to 6 weeks indoors or outdoors). Then I gradually add gears and my body is ready for the added stress.
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