Just picked up this news elsewhere:
"BROMPTON 6-SPEED WIDE RANGE HUB
Brompton is now offering a wide-range 6-speed internal gear hub as an option on all their models. Manufactured by Sturmey Archer, it will replace their current SRAM 6-speed hub. The new BWR, as they’re calling it, would make a nice upgrade for those who are currently running the S-A 3-speed or the SRAM 6-speed (which has a narrower range).
From the Brompton press release:
The new configuration for 6-speed Bromptons will feature a wide-range hub of our design, manufactured by Sturmey Archer; the present 6-speed arrangement, employing a SRAM hub, will be discontinued from 1 January 2009. We believe that the Brompton Wide Range Hub [BWR], together with Brompton’s derailleur system, sets a new standard in folding bike gearing systems. It offers:
An evenly-stepped gear range (302%) that is comparable to the leading 8-speed hubs; but
It uses only a single epicyclic gear train (instead of three), thereby maximising efficiency;
At 0.94kg, it weighs almost half as much as other hub gears;
It comes in the same small package as the current three-speed hub, allowing existing owners to upgrade easily; and
It is typically-Brompton: robust and built to last… owners can expect the same reliability as with the classic three-speed hub.
We will be supplying a 16-tooth and a 13-tooth sprocket with the BWR which, with a 50-tooth chain wheel, will give the following distances of travel:
Gear 1: 33.0 gear inches (2.63 metres along the ground)
Gear 2: 40.5 gear inches (3.23 metres travel)
Gear 3: 51.5 gear inches (4.11 metres travel)
Gear 4: 63.5 gear inches (5.06 metres travel)
Gear 5: 81.0 gear inches (6.45 metres travel)
Gear 6: 99.5 gear inches (7.94 metres travel)
This represents a gear range (top gear/bottom gear) of 302%; by comparison, the current SRAM 6-speed arrangement offers a range of 215%. Like our existing 6-speed offering, however, the gearing may be raised or lowered by fitting a 54-tooth (+8%) or 44-tooth (-12%) chain wheel in place of the standard."