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Over the past
few years the American magazines have been peppered with articles by knarly
old buggers romancing the single-speed mountain bike. I was finally seduced
last winter and opted to join the fray. My favourite tracks had lost a
little of their thrill of late and I was keen to spice them up. My other
motivation was to avoid trashing my shiny new XT drive chain over the
winter. The idea seemed easy enough ... pull the derailleurs off my existing
bike and go ride. It proved a bit trickier in execution. Here's my story.
A
few bits and pieces
•
A 2:1 ratio is the universally recommended gearing. To match my (standard)
32 middle chain ring, I found a dead screw-together XTR cassette with
a separate 16 tooth cog lurking in the nether regions of my tool box.
• My 99 XT shifter
pods and brake levers hang out together in the same unit. A mate came
to the party with some basic 'V' brake levers.
• Mountain bikes
have vertical dropouts - single-speeds have horizontal ones to take up
the chain slack. Not wanting to splash out on a new frame I needed a chain
tensioner. Specialist devices are available but pricey. Fortunately another
friend came to the rescue with a sloppy old LX derailleur.
• Wanting a clean,
light bike I replaced the front suspension with an old pair of rigid forks.
• All the magazines
recommended riser bars for extra leverage on the climbs and control on
the descents. They are 100% correct - flat bars don't cut it for a single-speed.
I couldn't scam any so had to shell out $35 for a set - my only expense.
• And the last requirement
is a pair of strong legs and over-sized lungs.
Putting
Frankenstein together
• The
chain line must be as straight as possible. Space the rear cog along the
length of the cassette until it lines up with the chain ring. For spacers
I used the old cassette spider, a couple of cogs, some proper spacers
and the lock nut.
• Bolt on the rear
derailleur and adjust the high and low screws so it lines up with the
rear cog.
• Now thread the
chain. Set the chain length so the derailleur jockey wheels are almost
parallel to the chain stay.
• Now the tricky
bit. Undo the 'B' adjustment screw until the derailleur body is about
3mm away from the chain stay when pulled forward by the chain. Using a
few trusty zip ties, tie the derailleur body as tight as possible to the
chain stay. This will leave the jockey cage free to move independently
of the rest of the derailleur keeping tension on the chain. This is the
secret to the single-speed conversion - before nutting this out I broke
my chain 3 times.
The
Proof is in the Pudding
Riding a single-speed
is the true born-again experience ... mainly because you have to operate
in a narrow speed band. Too fast and you run out of spin; too slow and
you stall. Momentum is everything. This forced me to ride new (better)
lines on tracks I've hammered for ten years. I'd blow through the corners
and stomp up short, grunty climbs. My bike handling skills improved because
I had to stay off the brakes, my pedalling technique improved from spinning
on the flats and of course it was great for fitness and strength. Curiously,
my average speed was only 3-4kph below my previous average for the same
ride. I was seldom too far behind my riding buddies, and in some sections
I would pull away as they delicately picked through some tricky bits that
I had just bludgeoned through - or maybe they were just being kind to
my ego.
And as a bonus, with
so few parts I hardly did any maintenance all winter. I saved all my good
gear for the next season and was riding a bike that weighed only 9.5kg.
Sensational!
My gears are back on
now and I am riding better than before and eager to tackle the race season.
But am even keener for next winter to roll around so I can return my bike
to its single-speed configuration. Now if I had a Voodoo Nzumbi frame
and a Paul's single-speed rear wheel - all I'dneed
to do is ...
by Owen Wing, June 2000
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