fastlane
22
tech
torque
Hooking up a Leaf Spring
Car without Traction Bars
STORY AND PHOTOS BY WAYNE SCRABA
Bolt-on traction bars for
leaf spring cars have been
available for what seems like
forever. Most work fine, but
we’re here to tell you that
people have hooked up leaf
spring cars without using
any traction bars.
Take a look at the stock appearing muscle
cars campaigned in the Supercar Races
Series. One of the quickest cars there, a
1969 Nova, has run a best of 10.48 seconds
at 132.34 MPH in the quarter-mile, with a
1.61 second 60-foot time. That’s hauling,
especially when you consider the car
runs on skinny belted bias-ply tires.
Then there’s the 1963 Max Wedge car that
ran a 10.94 at 126.60 MPH in 2013, and a
1969 Camaro that pulled a 10.49/134.77
pass in 2014. There are a bunch of other
cars hovering around the 11-second flat
zone, too.
How do they do it? Dig deep and you’ll
find all of the really quick leaf spring
combinations run springs with a decided
forward bias, where the front of the
spring is stiffer than the rear.
It’s not really a new idea, the Chrysler
[ 1 ]
Corporation came up with the concept in
the early sixties. Chrysler engineers knew
that when the hammer was dropped at
the starting line, the front of the spring
pack would wrap up, typically in an ‘S’
shape. They designed springs with a
heavier front bias; in some cases, the
springs were heavily clamped forward of
the axle housing. The back of the spring
pack was often run without clamps or
just a single clamp.
The aptly named ‘Super Stock’ springs
didn’t require any traction aid other than
a pinion snubber. In fact, Chrysler warned
racers not to use any traction device,
period. Mopar Performance still makes
Super Stock leaf springs: a testament
to how well they work. Summit Racing
offers Super Stock springs for you Mopar
guys.
Does that leave everyone else out in the
cold? Nope - thanks to oval track racing,
there are leaf springs for GM cars that
work much like the Chrysler Super Stocks
do. AFCO Racing makes leaf springs
engineered with a new secondary leaf
design that provides improved forward
bite. A bolt-in for various Camaros and
Novas, the AFCO springs are available
with several different rates, the most
common being 153 pounds or 176 pounds.
The 176 pound-rate springs are the most
popular for stock big block combinations.
AFCO leaf springs have an arch of
approximately 6 3/8 inches, which is
close to stock. They come with the front
spring eye bushing installed and accept a
stock rear bushing. The leafs are tapered
to reduce stress (30-40 percent according
to AFCO) and prevent the loss of arch.
Teflon rub blocks are placed between the
leafs to reduce friction and maintain the
springs’ rating over time.
One more trick out of the stock appearing
racer’s notebook is the use of extra
spring clamps. These can be used as
tuning tools for leaf spring cars with no
added traction devices. Summit Racing
offers several different bend clips for leaf
springs. Another option is to make your
own with a couple of heavy steel straps
and high strength bolts and nuts.
So does the AFCO leaf spring deal work?
The fast guys aren’t talking, but when
you see how hard many of those stock-
appearing muscle cars run, you can draw
your own conclusions. In the meantime,
let’s look at AFCO’s springs in more detail
in the photo captions.
At first glance, the AFCO leaf spring sold
by Summit Racing looks pretty much like
a stock replacement. But as you’ll see,
there are considerable differences