|A half-step plus granny triple crank. |
My first two touring/commuter bikes were set up like this
(48-44-24) back in the days of five and six speed freewheels.
Back when I started riding in the late seventies (nineteen seventies, that is), five speed freewheels were standard and sixes/ultra-sixes were just coming out. So wide range gearing on a touring or all-around work bike might involve a cogset such as 13-32 or 13-34, something along the lines of 13-17-22-27-34. Race bikes might have a 13-14-15-17-19 cogset in the flatlands of Long Island. My first "adult bike", a 1979 Motobecane Mirage, arrived with a 14-32 five speed and 52-40 chainrings; a gearchart was provided in the catalog.
On a work or tour bike, one could pair a wide range cogset with a triple crank having two main chainrings with only a 4 or 5 tooth difference between the big rings, and the granny, i.e., a "half step plus granny". Chainrings would be something like 48-43 (or 48-44) and a small ring, say a 24. The small percentage difference between the big and middle chainring, or "half step", in front let you split the gear ratio difference between those huge 4,5, and 7 tooth jumps in back. Dropping (carefully) into the granny ring got you up over the mountain. One would make a big shift in back and then fine tune with the 48 and 44 to settle into an acceptable cadence. Frank Berto presaged Lance Armstrong and the more recent trend that recognizes its better to spin up a grade than to crush your knees with overgeared bicycles. At sixty, that is even more important. Gear charts were used to calculate drivetrains (see chart below) to avoid duplicating ratios since there were fewer of them in those days of 5 speed freewheels. Gearheads would calculate optimum cogset and chainring combinations in those days and assemble them by hand from loose cogs (in pre-indexed days) with chain whips. Yes, I still have some chainwhips...
Gear ratios, in gear inches, from the gearing example above (48-44-24 chainrings from left to right, 13-17-22-27-34 cogset from top to bottom) on a nominally 26 inch wheel bicycle. Calculations from Sheldon Brown's Bicycle Gear Calculator.
|"Tell me all about those really low gears, Dave..."|
Anyway, have a great week.