I’m considering retiring my cherished 1998 Trek 5220 road bike. The biggest obstacle holding me back is that new bikes aren’t equipped with triple cranksets anymore. While I rarely use my granny gear, it’s comforting to know it’s there if I need it.
The bike I’m looking at has a double 50/34 (compact) crankset with a 11-32 rear cassette compared to my triple 52/42/30 crankset with a rear 12-26 cassette. Before buying a new bike I wanted to know how much range would be lost if I gave up my triple crankset, so I did the math as follows:
High Range Calculation
Distance traveled with each revolution of the pedals in high gear =
Wheel Diameter x Pi x Largest Chainring/Smallest Cassette Gear
28 inches x 3.14 x 52 teeth / 12 teeth = 381 inches
28 inches x 3.14 x 50 teeth / 11 teeth = 400 inches
Here a larger number is better.
Triple 52/42/30 crankset with 12-26 cassette = 381 inches
Compact 50/34 crankset with 11-32 cassette = 400 inches
Low Range Calculation
Distance traveled with each revolution of the pedals in low gear =
Wheel Diameter x Pi x Smallest Chainring/Largest Cassette Gear
28 inches x 3.14 x 30 teeth / 26 teeth = 101 inches
28 inches x 3.14 x 34 teeth / 32 teeth = 93 inches
Here a smaller number is better.
Triple 52/42/30 crankset with 12-26 cassette = 101 inches
Compact 50/34 crankset with 11-32 cassette = 93 inches
I was surprised to find that the compact crank setup would give me a greater high range but I was downright shocked to learn that it would give me a better low range as well.