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Issue link: https://magazine.cyclenews.com/i/125792
with the rider as to his needs helps to
settle on a final design. The same applies
to Trials work, where Curnutts are
finding increasing acceptance. Tuning
the shocks for the rider and type of
riding is most improtan t, and it's
recommended that you bring.your scoot
in for the first "fitting" of your shocks.
But why bother with Curnutts? They
settle, using up some of the useful
travel. They make funny noise. They
look funny. Even if they are fairly
simple to rebuild, your comer dealer
probably doesn't stock the parts. So
why bother? Well, according to Chuck
Curnutt, if you're going to have the best
suspension, it has to be specific.
Generalized solutions are not the
answer. If you're going real slow on
motocross shocks, they'll top out, but
will do the job when you get up to
speed. Trials shocks work just the
opposite. The reason for allowing the
shocks to settle is that most bumps are
actually holes, so you need some
downward
travel available in the
suspension to allow the rear wheel to
drop down. A rock is one of the few
cases where a wheel bounces up. So
two-way travel (with about two inches
of settling on a five inch shock) is
important to let the wheel go both up
and down. This keeps the rear wheel in
can tact with the ground, and driving.
Curnu tts also have a single floating
valve within the shock tube that
preven ts the rear end of the bike from
squatting down when accelerating or
negotiating ripples at high speed,
thereby using up useful shock travel.
That is about the only moving part.
There are· no rubber bumpers on
Curnutt shocks. A shock shouldn't
bottom under regular competition use.
Well, ma.ybe it should bottom about
once per lap in MX but when it does,
the rider should be aware of it and not
have bumpers to hide the fact.
Bottoming causes the side-hopping of
bikes
over
the
rough,
like
whoop-de-doos, and can make a rider
high·side if he tries to increase speed
and doesn't back off some.
What is this marvel shock that allows
the subtle tuning of the suspension to
the bike and rider? Well, actually it's
not much at all. With expectations of
some complex system of bleed orifices
and graduated washers, pipes and fluid
return
tubes,
it's
almost
a
disappointment to see the workings of
the Curnutt.
Tile first Curnutts were just a simple
dash pot: a piston in a tube of fluid.
They havn't changed much. Chuck
eventuall
ut in a valve to sto the
The working part of a Curnutt shock. What
you see is all there is.
The Curnutt stickie and springs to match rider
weight and competition event go on before
oscillation that occurs in cornering. And
that's the way Curnutts are today.
There's a piston with four small boles in
it attached to the steel shaft and a valve,
with one hole in it, around the shaft.
The valve floats above the piston
providing downward dampening only at
low speeds and two-way dampening at
high speeds.
This little assembly gets. tucked in a
metal tube of ATF. That's it, The
Curnutt shock. You can't really say
much about the mechanical workings of
it excep t that it does seem to work.
Sometimes it works very well indeed
where more complex designs don't
make it. Curnutt claims the valve can be
adjusted to accomplish anything you
desire from the suspension, but this fine
tuning is more art than science, acquired
over the past 15 or so years. The
Curnutt shock now represents an
optimum design for simple practicality.
Any further tuning of the suspension is
very sublte.
How did the Curnutt shock get that
way in the first place, when most other
designs are 180 degrees the other way in
their approach. Curnutt explains it.
"It helps to deliberately avoid
studying what other people do. A lot of
what they do is wrong. I've never even
had
another
kind
of
shock
apart...except an old Ford shock some
years ago. Tradition is so strong in
motorcycling - they haven't changed in
years. There are plenty of experts to
show why change is wrong. There are
good riders who won't go as fast on a
changed thing and that proves it to
them"
He
con tinues with
an
almost
whimsical gleam in his eyes, "I've got a
lot o( little projects going on now, that
are really going to surprise some
people." He later hints that the first big
change in Curnutt suspension units, and
other stuff, may be forthcoming in the
not too distant future. My curiosity is
whetted but further questions get no
more information, just that gleam in the
eyes.
Charles Curnutt has been approached
more than once to build the all-purpose
shock to fit any bike and accommodate
the median "percentile" rider. He
refused because such a shock wouldn't
work as well as a Curnutt tuned shock.
Charles Curnutt couldn't really put his
name to an inferior shock absorber.
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