The gear ratios shown on the Rohloff site are 32:13, 38:15, 40:16 and 42:17, so factors of 2.461, 2.533, 2.5 and 2.470. Difficult to see much difference between 2.437 and 2.461, but I'm very wary of causing any damage to such an expensive component.
Pete, I ride a 29er as my everyday bike, and in my street clothes, which I wear for cycling, I weigh near enough 100kg.
There are three things you have to understand about Bernd Rohloff, the designer of the gearbox you want to buy. The first is that he is German manufacturer, and that even among German manufacturers he is a master of CYA, covering his ass (more politely, protecting his brand's reputation for longevity) with extremely conservative usage ratings and service intervals; there are remarks in threads here and there on this forum about precisely how conservative these ratings and service schedules are, and it makes remarkable reading; in any event, Rohloff's permitted chainring/sprocket ratio that determines the torque fed into the box has been reduced twice in the last decade, i.e. Rohloff admitted each time that it could handle more power than previously stated as the unalterable maximum for the ages; I, for one, don't believe we've seen the last relaxation of these still-conservative ratings. The second is that he is a designer of German agricultural machinery intended to serve your great-grandchildren as faithfully as it serves you; a Rohloff is a heavy box not because Herr Rohloff is an incompetent engineer, or not a cyclist (he's very competent indeed, and a cylist as well) but because it is deliberately the antithesis of the "cheap, light and reliable, choose any two" Lotus paradigm. The third is that the Rohloff gearbox is designed to shrug off the abuse of being ridden on sand-dunes and wet beaches because its design was quite literally inspired by derailleur bikes on his honeymoon self-destructing in protest at being ridden on a beach. It was never intended as a refined touring box, but instead is a mudplugger's box; touring installations happened by accident.
While, like George (Mickeg), I would never advise anyone positively to breach the warranty conditions on such an expensive component, I'll tell you what I would do, in consideration of the above: First, I'd keep the supplied sprocket of 16T and run it with a cheap, probably steel, but permitted chainring until after the box is proven. By this I don't mean run in; as the great Chalo Colina said, a Rohloff box runs in at the kind of mileage where a Shimano hub gearbox lies down and dies (I trashed a couple before 5000m). What I mean is that you have to understand that there's quite a bit of hand-fitting in a Rohloff, so it rubs in the gears in the first couple of thousand miles (you'll see quite a bit of ground steel come out in the first oil change -- use a magnet in the dirty oil to see it, or rub the dirty oil between your fingers to feel it). This is also the time when, if it will break, it will break, so you may want it replaced under warranty. After a couple of thousand miles or after the first service at three thousand miles I'd buy the chainring I really wanted and fit it regardless because the chances are that, unless one abuses the box grotesquely, one won't ever require warranty service.
The first table at
http://coolmainpress.com/BICYCLINGHebieChainglider.html contains all the gear-inch and speed combinations for each of the Rohloff gears for selected torque transmission (Chainring/Sprocket) sets for a 29er. Ask if you want another ratio calculated and I'll feed it into my spreadsheet.
Good luck.
PS: Better to reopen a relevant old thread than to spray pieces of the same discussion all over the forum. Anyway, this is one of those perennial ever-fresh threads.
