Originally Posted by
riverdrifter
I'm not sure I really even understand what half-step gearing is. I'm sure I have a normal triple now 52-42-30, on my Jamis. I live in the flatlands, is half-step gearing more for mountains? The Trek is from the flatlands too, so maybe that's why it got swapped to a normal triple?
Half step gearing is complicated but it lets you eke you more useful gears when running 5 or even 6 on the back than if running crossover. Sheldon Brown has a good explanation:
"In the days of 4- and 5-speed
freewheels , 8- and 10-speed bikes were commonly set up with chainwheels that were very close in size, for instance, 46/49, or 47/50. When used with typical freewheels of the era, the difference between the two front gears was about half as large as the difference between adjacent gears on the freewheel. (One reason for this was that early front derailers couldn't handle much more than a 3-tooth difference reliably!)
With half-step gearing, the larger shifts were made with the rear derailer, and the front was for fine tuning. This allowed an 8- or 10-speed set up to have a reasonable range with fairly close spacing of the gears."
My Olmo Gran Sport from 1960 came stock with half step gearing but then the gran sport front derailleur can't handle a big jump. The bike has a 49/46 up front and a 14-26 5 speed freewheel. Shifting through the gears involves a lot of double shifting which is a pain.