Originally Posted by

**John E**
A bit more detail regarding my half-step-plus grannie system -- A 3-tooth drop in front (49-52, 47-50, 46-49, etc.) with a 2-tooth progression in back is traditional for close-ratio half-step gearing, because the ratio change in front, about 6 or 7 percent, is half the average percentage change in back, from 13 to 15 to 17 to 19, or from 14 to 16 to 18. I use a 110/74mm BCD mountain crank with a mix of SR and QBC rings from eBay. I like a top gear of about 48/13 or 52/14, i.e., 100 gear inches. In front, the 34-45 shift is the same drop as a 42-53, which any older-style derailleur, such as my Shimano 600, can handle easily. Interestingly, 34-48 is the same 14-tooth drop as today's road standard, 39-53, so my 34-45-48 / 13-23 combination does not tax the rear derailleur any worse than a 39-53 / 14-24 would.

For the transportation or recreational cyclist, half-step gearing works out extremely well. I accelerate through the gears one cog (i.e., two ratios) at a time, then, as I reach cruising speed, I can fine-tune as needed by shifting between the 45 and 48 rings. For an extra-fast, extra-smooth start, I dump the chain onto the grannie before stopping (or while stopped, by lifting the rear wheel). As I start up, I spin up to about 100 rpm, make the 34-45 shift, then start working through the rear cogset as needed.

Leaving out the two cross-chains and allowing for the convenient redundancy at 61 gear-inches, I get 15 good ratios out of 18 possible combinations:

___48__45___34

13 99.7 93.5

15 86.4 81.0 61.2

17 76.2 71.5 54.0

19 68.2 63.9 48.3

21 61.7 57.9 43.7

24 ____ 50.6 38.2

(I have used 13-23 and 13-24 freewheels on this bike, but 45/23 does not interleave between 34/17 and 34/19 as neatly as 45/24 does.)