NASCAR Trucks: Page 2
The Gloy-Rahal Racing truck goes on track for a practice run.
This is a Ford truck. Notice the positive camber on the left
front tire. Also the fender flare. At Martinsville, a 5/8-mile
flat track with a mid-corner speed of 60 mph, they run 7 or 8
degrees positive camber on the left front wheel. You can see
the sidewalls wrinkle when they push the cars (Winston Cup and
Trucks) around in the garage area. Ron Barfield is the driver
of the 55 truck.
Hendrick Motorsports' Chevy truck driven by Jack Sprague the
fastest qualifier at 28.037 seconds.
Another view of the 24 truck, a Chevy, next to the Ford of
second-fast qualifier, Rick Crawford. Notice the fender flares.
A closer look shows an adjustable support for that fender
flare. On superspeedways the fenders and wheel cutouts are fitted
to the tire very carefully to minimize aerodynamic drag. On shorter
tracks like Phoenix the fenders are flared out to produce downforce.
If the bodywork behind the tire can be curved so the trailing
edge of the tire sticks out away from the sheet metal behind
it, the tire becomes a pump pushing air out from under the car
increasing downforce on the front of the car. I'd guess the right-front
tire, when turned into a corner would pump enough air to make
The production Dodge truck is bigger than its Ford and Chevy
counterparts so the race truck is scaled down to make it more
compititive with the other trucks. This truck was driven by Stacy
Compton, starting in sixth place, the best qualifying Dodge.
Notice the lip on the edge of the flares. This acts like a Gurney
flap, lowering pressure behind it and increasing flow from under
the front of the car, at a drag penalty of course.
The fender flares on the Ford trucks have the Gurney lips
also. Each manufacturer spends a lot of time and money on wind
tunnel testing. Some teams also do tunnel testing. Looking at
these photos the Dodge and Ford front ends look smoother to me.
I wonder if the Chevy truck doesn't have a little more drag than
the others. If I'm right it doesn't keep them from winning.
Trucks Page 3