Trying to flip a coin on the preferred chainring group for my 50 cm Rivendell Saluki. I'm 5'3", my PBH is a smidgen under 76 cm, and my SH is 64.5 cm.
The bike is a bit on the heavy side, lugged steel frame, and it may wind up with more weight: fenders, a small rack, and small bag on rack for metropark whatnots, and for possible credit card tours.
The majority of bike riding on this bike would be on pavement in metroparks. When doing club rides in the metropark, there are some segments where I would need to have a 15 MPH pace. But on the average, I suppose a 30 mile club ride in the metropark will have an average between 12 & 14 MPH. I've only ridden in one metropark, so I can not really mention whether or not metroparks in Michigan will typically have any significant inclines.
I did a 25 mile club ride Sunday on my Trek 730 (see avatar below), which has an 11-28 cassette with 170 mm - 42/34/24. These were comfortable gears, but it was a strain to keep a sustained speed of 14 MPH. I should add I was only doing about a 65-70 RPM cadence, until I get the engine tuned up to an eventual 80 RPM cadence.
The Saluki will be on 650B x 33mm Maxy Fasty tires, the rear cassette will be Ultegra 12-27 (9 speed), and the following crank options are all Sugino XD2 cranks:
* 165 mm - 46/36/24
* 170 mm - 46/36/24
* 170 mm - 48/36/26
Any advice on selection (and reasoning on selection) of crank and chainrings, based on the bike ... bike weight ... bike accessories ... 650b wheels ... 50-year age ... and the riding style I described?
I would take your pre-this bike's chainrings and cassette numbers over to the Harris Cyclery gear inch calculator, and play with the various options, so that you can find a set of ratios that work out the same as the ones you have experience with. Then you can figure out whether there is some combo that allows you to use a more favourable density in your cassette. For instance if you moved down from a 700 wheel then your new cassetes could have tigheter ratios while retaining the same range, or if you moved up from a 26" you would need more cassette range to get the same range in your larger wheels. That sort of thing. What you want is the maximum gear range, the maximum number of intervals, the smallest jumps between gear, and you either want a linear rate of change between gears, or you don't, depending.
This is also a time to ask yourself whether you have the right crank length. If you do OK, if not, you can use the gain ratio feature the gear calculator has to include that factor to keep your effort/cycle the same. Use the Zinn site for crank calc.