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Does a Rohloff Speedhub make you fitter? Notes about sprocket ratiochoice.
I'm probably somewhere between a masher and a spinner, and too old to
learn proper cadence control even if I wanted to. But in any event I'm not at all certain cadence would be more advantageous to me than my present method of controlling exertion by respiration rate. Controlling exertion by heart rate rather than cadence works for me to such an extent that I must be much fitter than I was even last year, despite the fact that through this miserable winter (bring back global warming!) I've ridden only 650km since the beginning of the year. How do I know I'm fitter? I very carefully calculated the gearing of my new Rohloff hub gearbox by reference to two successful Shimano Nexus-equipped bikes. The idea was to give me three extra gears below the Nexus to get up the steep hill before my house, and to ignore the fact that two extra high gears on the Rohloff would be wasted. The point of buying the Rohloff was thus not the 14 gears per se but the spread of useful ones within the Rohloff sprocket ratio restriction of 2.375, within which I chose 38/16. So the Nexus-equipped bike would have gear inch ratios from 27.3 to 83.8, mountain bike territory, with which I lived happily for five years, while the Rohloff-hubbed bike would have ratios from a goats- only low of 19.5 to a road-racer's 102.6 gear inches. The Rohloff bike has three gears below and two above the Nexus, which doesn't add up right: there is a ratio gap in the Nexus box between gears 4 and 5 into which the Rohloff fits an additional gear -- see the table below. Another way of looking at it is that I chose my sprocket ratios to match my expected speed on the flat of 20kph at my usual cadence of 60rpm in the direct 1:1 ratio which on the Rohloff is gear 11. In the table below the Shimano Nexus ratios are arranged for nearest correspondence with Rohloff gears. Now I find that I'm often in the two high gears on the Rohloff that I expected to be wasted, pulling 103 gear inches on the flat and slight uphills. The fact that my new Rohloff bike is about 5kg lighter than the old Nexus one simply cannot account for that much newfound speed. When I first calculated that 103in gear, I laughed aloud; that's road racer territory, I though, my bum in the air -- never going to happen! My average speed has also crept up to where last night, back home from a standard ride, I noticed my average speed was 14.8kph, where last year for the same ride it was somewhere between 12 and 13 kph. That's not all. I now find that the lowest gear isn't necessary for pulling up the steep hill before my house (up which a lot of impressive cyclists push but I ride). As I say, i dunno if this is me getting fitter, or just using the gears more because I have them, but I would suggest to people considering buying a Rohloff hub that they calculate the sprocket ratio very carefully indeed. You can't have too many low gears but under 20in might be *too* low except for climbing walls, and a high of 103in now doesn't seem excessive even for a less than pacey cyclist. See the table below. Andre Jute Visit Jute on Bicycles at http://www.audio-talk.co.uk/fiultra/...20CYCLING.html Comma-delimited table for reconstruction x, x, x, x, x, x, x x, DATA, x, x, x, x, x x, Rohloff 14, x, x, Nexus 8, x, x x, 38 x 16 = 2.375, Chainring/sprocket, x, 38 x 20 = 1.9, Chainring/ sprocket, x x, 60 x 622, Tyre, Big Apple, 37 x 622, Tyre, Marathon + x, 29.45, Circ inches, x, 27.3, Circ inch, x x, x, x, x, x, x, x x, COMPARISON, x, x, x, x, x Gear number, Rohloff 14, x, x, Nexus 8, x, x Rohloff/Nexus, Ratio, Gear inches, kph @ 60rpm, Ratio, Gear inches, kph @ 60rpm 1/-, 0.279, 19.5, 5.6, x, x, x 2/-, 0.316, 22.1, 6.3, x, x, x 3/-, 0.360, 25.2, 7.2, x, x, x 4/1, 0.409, 28.6, 8.2, 0.527, 27.3, 7.9 5/2, 0.464, 32.5, 9.3, 0.644, 33.4, 9.6 6/3, 0.528, 36.9, 10.6, 0.748, 38.8, 11.1 7/4, 0.600, 42.0, 12.1, 0.851, 44.1, 12.7 8/-, 0.682, 47.7, 13.7, x, x, x 9/5, 0.774, 54.1, 15.6, 1.000, 51.9, 14.9 10/6, 0.881, 61.6, 17.7, 1.223, 63.4, 18.2 11/7, 1.000, 69.9, 20.1, 1.419, 73.6, 21.1 12/8, 1.135, 79.4, 22.8, 1.615, 83.8, 24.1 13/-, 1.292, 90.4, 26.0, x, x, x 14/-, 1.467, 102.6, 29.5, x, x, x x, x, x, x, x, x, x |
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