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+ON TEST
clicks neatly into its socket on the
handlebars, and offers four power
modes with three levels of assist in
each – overly complex perhaps, but if
you’re like me you’ll leave it on full
blast mostly, anyway. The display is
good and clear, with the usual speed,
battery status and distance displays.
The Bosch drive is fitted with a
pulley for the Gates belt drive system,
which runs without oil or grease
lubrication back to the rear hub. It’s
almost unaffected by mud, and won’t
go rusty like a chain which gets wet,
so it’s a promising choice for an MTB.
The belt is also lighter than a chain,
and Gates claim excellent durability.
It’s especially good for a crank drive
e-bike, as these can be hard on chains.
The hub which it drives is the
NuVinci N360. NuVinci are the
only manufacturer of continuously
variable drives for bikes – unlike
conventional gear systems, there are
no steps between ratios. Instead, you
can vary the ratio continuously, by
twisting the handlebar grip, over a
range of 3.6:1. This is about the same
range as a single-chainring derailleur
system. The clever display on the
handlebar control shows instantly
which gear you’re in via a line that
goes flat (for high gears) or hillshaped
(for low ones).
The technology is now well proven,
and after several years of production
these hubs have a reputation for
toughness, even on cargo bikes and
other heavy duty applications. Good
for off-road use, then. The only
question mark about the NuVinci is
efficiency: reliable numbers are hard
to come by but it’s generally thought
to concede only a little to a clean
derailleur drive.
The hub is mounted in heavy duty
adjustable dropouts (for setting belt
tension) which, like the rest of the
frame, look solidly made to withstand
some off-road abuse. One rather minor
criticism is that there are no bottle
cage mounts provided.
The rest of the equipment on the
MX is high quality stuff. There are
SRAM Elixir hydraulic disk brakes, a
good set of suspension forks (Rock
LEFT: The Bosch drive
system is neatly built into
the frame, and is fitted
here with a pulley for the
belt drive rather than a
conventional chainring.
BELOW LEFT: The
belt drive needs no
lubrication and is almost
maintenance free. Note
the sliding dropout
system, clamped with two
bolts, which allows you to
adjust belt tension.
BELOW: The control unit
clicks into place with a
quick twist, and provides
a clear readout.
Shox Sektor RL), and wheels shod
with grippy 2.4"-wide Continental
MountainKing tyres.
One jarring detail was the dynamo
lighting system, a quirk of the
German road traffic regulations,
which make such things compulsory
for bikes over a certain weight. This
is clearly something of a token
gesture here, with a basic bottle
dynamo. 2013 bikes will have a neater
system fitted, anyway.
The dynamo system may also
account for some of the difference
between the weight quoted (23 kg)
and what we measured: 25.0 kg, both
including the battery. It’s rated for
an impressive 140 kg maximum rider
weight.
» OFF THE ROAD
If, like me, you’ve not ridden off
road for a while, the first ride on
the MX will be quite an eye-opener.
Setting off up a rough, muddy track
it was quite remarkable how those
fat, knobbly tyres both grip through
the muck and cushion the ride. The
wide handlebars provide the leverage
to hold the bike on course even as
the front wheel is slipping around
over ridges and tree roots, with the
suspension forks smoothing the worst
of its impacts.
With all this going on, I’d almost
forgotten the Bosch power assist: it
was adding to my leg power smoothly
and unobtrusively. As a ‘torque sensor’
type drive it measures your effort and
adds to it, so it feels like your legs
are supercharged, without any sense
that it’s taking over. So you retain
the ‘feel’ and ability to finesse the
power delivery to manoeuvre the bike
around obstacles.
What it does remove is the pain and
effort, leaving you to concentrate
rather more on your technique (in
my case, staying upright!). Obviously
this is the case on hills, but also for
those short bursts of power which you
need to restore your momentum or
regain balance.
The drive does have a slight buzz
to it, especially if you spin the pedals,
but it’s not enough to disrupt the
off-road experience. Nor did I find the
bike’s extra weight much of an issue
when descending – as a fairly cautious
off-road novice I wasn’t exactly
pushing the boundaries, of course, but
it seemed to hold its line well down
singletrack trails, with the suspension
12 Electric Bike Issue 6