In both
runs the GM truck beat the Ford up the hill. The Ford could get a better
launch but by about half-way up the grade the
Chevy caught and passed the Ford. This isn’t to say there
was a large gap between the trucks at the finish. There wasn’t.
It never grew to more than about a truck length.
I’d
chalk GM’s
advantage in this sprint to its six-speed transmission. First gear for
both trucks is almost identical, 3.10:1 in the Chevy’s Allison
gearbox to 3.11:1 in the Ford’s five-speed
TorqShift. The Ford had a takeoff advantage but the Duramax reaches
660 lb-ft peak torque at only 1,600 rpm to the Power Stroke’s 650
lb-ft at 2,000 rpm. And in second gear the Allison dramatically rises
to 1.81:1 compared to the TorqShift’s 2.22:1.
The Silverado used its earlier torque and second gear to brute force
its way past the F-250. By third gear they were more evenly matched again
- 1.41 in the Allison to 1.55 in the TorqShift - but by then it was too
late. Momentum had shifted in favor of the Silverado.
We took
the same trucks and also ran them through a coned slalom course designed
to let the driver determine which truck they felt more comfortable
towing in when executing rapid and tight turns at speeds up to 45-miles
per hour. I’d say they both felt just about the same with a slight
edge to the Silverado. Remarkable when you consider the platform and
suspension differences in both trucks.
The wet
skid pad test was to demonstrate and subjectively evaluate differences
between the light duty Chevrolet Silverado’s StabiliTrak and
Toyota Tundra’s Vehicle Stability Control (VSC) electronic stability
control (ESC) systems.
ESC is an
increasingly important safety feature for cars and trucks. It works
by combining antilock brakes (ABS) with automatic traction controls
- like individual or multiple wheel braking and throttle reduction
or shutdown, to help drivers avoid a crash in slick conditions. It
does this by measuring vehicle speed, steering angle, and target versus
actual yaw rates against the slip rate of each wheel relative to the
ground passing underneath. If a wheel’s
slip rate is approaching the vehicle’s
predetermined stability limit, the ESC system can restore stability by
decreasing engine output and braking front or rear wheels to reduce the
slippage and help maintain control.
ESC is proven
too. According to the Insurance Institute for Highway Safety (IIHS),
their research shows that ESC reduces the risk of all single-vehicle
crashes by more than 40 percent and fatal ones by 56 percent. The federal
government’s National
Highway Traffic Safety Administration (NHTSA) has mandated that by 2009
55% of all vehicles will have to be equipped with an ESC system and 100%
by 2012.
Mike Rizzo,
lead engineer for chassis controls at GM, says the automaker has invested
over $10 million dollars creating two extreme skid pads to test their
ESC solution on. We drove the ‘less aggressive’ basalt
tile pad, which has a kinetic (i.e. sliding) friction coefficient, or μ,
of .25 to 3 – a surface more slippery than snow. In comparison,
rubber tires moving on dry pavement have a μ of about .8. The second
traction pad uses ceramic tiles for an even slipperier surface rating
of .12.
