45-42-24 X 12,14,16,18,21,24,28,32,36
In another gearing thread a few weeks ago (Touring with a double) I suggested I wanted to try an old school ďHalf step with GrannyĒ and do it with a modern 9 speed cassette and STI shifters. With some help from the folks over on the Bicycle Mechanics Forum I went ahead and bought a 45t Rocket (Chop Saw like) chainring off Amazon for $14. No ramps no pins 3/32 width. Some of the possible problems were lack of pins and ramps, tooth depth too deep as itís a single speed ring and FD designed for a 10 to 12 tooth lift and I only needed a 3 tooth jump. Happy to report none of these became an issue. I was able to drop my FD about 3/8 of an inch keeping the inner shift plate as close to the 42t ring as I could without rubbing when it shoves the chain over onto the 45t ring. There is still a gap between the outer shift plate and the new big ring, but the shift is as smooth as butter in both directions. Lowering the FD put it in a better place even with the granny ring and eliminated all the trims on all the rings with the GI listed below that are the only ones I ever use. I may still shorten the chain (donít know) it does go slack on the smallest cogs but I donít know if thatís a problem as the RD is nicely angled to use all the cassette with both larger rings even though I donít see cross chaining off the 45t.
Doing the half step shift is really simple and in riding it I donít try and run up and down the half step pattern like the old 10 speed days, but use it as a simple one shift in the front or a double shift front and back to get an in-between gear. The double shift is simple to think about as its ether both silver levers or both black levers. The front shift feels every bit as smooth as a rear shift. The shift up from the 24t granny to the 42t was always a tough shift but lowering the FD seemed to make that smoother also.
The unexpected result of this is benefit of the straighter chain line on the 3 smallest cogs. I didnít think too much about that ahead of time. But it was the first thing I noticed as I never had much use for those cogs off the old 52t. That straight chain line feels very smooth compared to getting close to the same GI coming off the center ring. It could be just a new smooth ring with little wear but others tell me itís the straighter line.
I think this is a keeper for me and I donít see myself going back or dropping the outer ring altogether. I might try and fit something like a 48t chain protector to the chop saw ring, for looks and keeping my pant leg clean. Not sure yet.
Well just wanted to post what I ended with and photos below in case anyone wants to try something similar.
My Granny without cross chain will give me this GI range. (6 gears)
And my main rings with half step will give me these without cross chaining. (15 gears)The ones shown with the minus sign are the new half steps off the 45t.