It’s something anyone who has ridden
or watched motocross knows – a rider
can adjust the height of the front
wheel in relation to the rear in the
air by applying brake or throttle. And
it’s possible to do the same in a race
truck that weighs 20 times as much.
The physics is simple. The wheels
are rotating. If a driver applies the
brakes, the kinetic energy of spinning
wheels has to go somewhere, and
the truck rotates. It’s Newton’s third
law of motion – the one about an
equal and opposite reaction. It’s a
small effect, because the wheels are
a much smaller mass than the truck
itself, but it allows the driver to control how he flies and lands, and not
just be a passenger during the flight.
“On the big tabletop at Lake
Elsinore, out of Turn 3, we fly almost
200ft,” explains Carl Renezeder.
“I leave the face of that jump 100
percent on the throttle, which tends
to make the nose come up. I drop the
front end in the air so I can fly and see
where I’m going, then give it gas to
drop the rear for a smoother landing.
It depends on the jump whether I
want to land on the front tires or on
the rear. I control that with my throttle
position coming off the jump and
then my throttle and brake coming
through the air. It’s seat of the pants;
I can’t tell you exactly how I do it.”
SUBTLE BRAKE OR THROT TLE CAN
“STEER” A RACE TRUCK IN THE AIR
“The difference between
running in sixth place or
running first through
third is big”
the turn early, stay closer to the inside, and
you see you’re making up time, you have to
be patient and you have to anticipate. In a
Pro 4, you just do it. You get the
opportunity and you just do it now.”
There are other differences, of course.
Renezeder says a Pro 4 can snap roll easier
than a Pro 2 if it hits a rut mid-corner. But it
also has the ability, on occasion, to pull itself
back when it’s on two wheels. In a Pro 2, all
doesn’t answer the question of whether
one is better than the other, or easier to
drive. Where should a driver moving up
from Pro Lite or some other class go?
“Pro 2 is probably an easier truck to
drive as far as getting in and just going
around and doing laps,” Renezeder says.
“But to be fast, really fast and lead the pack,
it’s very hard in both trucks. Bottom line is
that, to be top level and running up front,
they’re both difficult to get to that point.
The difference between running sixth place
or running first through third is big. That
extra half-second…to pick that up is where
it’s at. Both classes are similar that way.”
Renezeder says the depth of guys that
can win is pretty similar in both classes,
even if Pro 2 has more trucks overall.
Given that, if he had to make a choice…
“It would be Pro 4,” he says without
hesitation. “When you get a good race
going with Pro 4s and you get three,
four, five guys battling it out, there’s
nothing like it. It’s just back and forth.
Winning a race is secondary. It’s the
strategy and the aggression and the
control and the passing back and forth
that’s really awesome in Pro 4.”
(ABOVE) If he had to
choose one (which he
would take his Pro 4.
(LEFT) This is pretty
rare, but Pro 2 and
Pro 4 shared the
track at last year’s
Challenge Cup in
Lake Elsinore, Calif.
you can do is steer yourself out of it and end
up losing time. The Pro 2 is typically faster
through whoops or other rhythm sections
because it doesn’t carry the weight – largely
unsprung – of front CV joints, axles and
differential. But a Pro 4 can hit an obstacle
faster if there’s one right out of a corner.
One of the biggest changes is how
much each truck can adjust its attitude in
the air. By applying throttle or hitting the
brakes, a driver can adjust the nose-up or
nose-down attitude when it’s mid-air over
a jump (see sidebar). In a Pro 2, though,
once he hits the brakes, the front wheels
are stopped and won’t start spinning again
until you hit the ground. In a Pro 4, you
can get them going again with the throttle.
How what seems like a small difference
– turning a second set of axles – affects how
a truck drives and races is intriguing. But it
carl renezeder gets the nose down off
the big tabletop jump at lake Elsinore.