vernon said:"Rob Morley" <[email hidden]> wrote in message
news:20080517125551.567983be@bluemoon...
Quoted message said:
There's no reason hub gears won't handle moderate off-road use -
they'll generally cope with stray twigs better than derailleurs do. The
downside of hub gears is they tend to weigh more than
derailleurs, they're a little less efficient and don't have as wide
a range of gears. They can also be very expensive. The upside is
that a better chain line can be maintained and all the workings are
protected within the hub.
Hub gears are usd in the Thorn expedition range of bikes and I'm sure
that I've seen some hub gearsed MTBs. Although the bikes that I'm
referring to are 14 speed hubs from Rohloff, the principles are the
same for any hub geared ike. There's no mechanisms to damage. Chains tend
to last longer because there's no lateral flex caused by
derailleur gears. The makers of the Thorn range of bikes claim that
there's no weight disadvantage when the gear mechs and levers are
compared i.e. derailleur shifters and mechs from front and rear vs
the hub gear. Efficiency isn't really an issue unless one is trying
the extract every last ounce of performance from a bike.
The only downsides that I can think of, and they are minor, is the
faff of removing the rear wheel to replace inner tubes when suffering
from a puncture and the need to adjust the rear wheel periodically to
maintain chain tension. Thorn bikes have neat fixes to attend to
these issues i.e. eccentric bottom bracket mount and some cleaver
connectors to facilitate wheel removal. I don't know how other
manufacturers approach these two problems.
Rohloff is exceptional and extremely expensive. There is a weight
disdvantage with more affordable hub gear systems such as Shimano Nexus (the
hub weighs a ton), and removing the rear wheel is such a faff that a lot of
ordinary owners would have to get a bike shop to do it for them. Chain
tension only needs to be adjusted after the chain has stretched, which
should take some thousands of miles. This is done manually via wheel
positioning.
However, the advantages of the ease of gear-shifting and low maintenance of
a Nexus system can make it well worthwhile to anyone who wants to cruise
along at modest speeds and doesn't need a wide range of gears - on off-road
paths as well as roads.
Fitting hard-wearing and highly puncture-resistant tyres such as Schwalbe
Marathon Plus will make tyre and tube changes a rare occurrence.
The rear roller brake option reduces maintance and cleaning further, and
works better than a rim brake in wet weather.
~PB
