I am much more interested in how fast I can ascend, rather than descend. The highest gears on my road bikes are in the mid-90 gear-inches (e.g. 46/13, 50/14), and I have a 104 (48/12) on my mountain bike, and all of those are perfectly adequate for me. According to the velometer on my mountain bike, my maximum speed has been around 50kph, or 30mph (on road -- I would never go that fast on dirt).
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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