If you want some lower gears, consider using your 48 as your outer ring and replacing the 52 with either a 45 or a 44. If you want to keep your 100-inch top end, you'll need a 13T high gear cog instead of your current 14. I would vote for something like: 48-45 / 13-15-17-19-22-25-28. (Been there ... done almost that, with a 48-45-34 / 13-15-17-19-21-24 setup on my PKN-10.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069