Table 3A

Understeer Gradients for SUV Models
With Data Available from Multiple Sources


Vehicle Model Year Drivetrain Source Data Reduction* Understeer Gradient (deg/g) Standard Deviation** (deg/g) 95% Confidence Interval**
Lower Limit Upper Limit
Ford Explorer                
w/SLA Front Suspension                
4-Dr. 1996 4X2 Guenther   2.04      
4-Dr. 1996 4X2 Guenther VRTC 1.96 0.15 1.80 2.12
4-Dr. 1996 4X2 Ford   2.9      
4-Dr.w/OE Goodyear tires 1996 4X2 Guenther   1.84      
4-Dr.w/OE Goodyear tires 1996 4X2 Guenther VRTC 2.11 0.16 1.94 2.27
4-Dr.w/non-OE Goodyear tires 1996 4X2 Guenther   1.97      
4-Dr. 1997 4X2 Ford   3.1      
4-Dr. 1998 4X2 Ford   2.2      
4-Dr. 2000 4X2 Guenther   2.20      
4-Dr. 2000 4X2 Guenther VRTC 2.33 0.10 2.22 2.44
                 
4-Dr. 1996 4X4 Ford   2.5      
4-Dr. 1997 4X4 Guenther   2.59      
4-Dr. 1998 4X4 VRTC   2.58 0.31 2.25 2.91
4-Dr. 1998 4X4 Ford   2.8      
                 
2-Dr. 1999 4X2 Guenther   1.86      
2-Dr. 1997 4X2 Ford   2.19      
                 
Ford Explorer                
w/Twin I-Beam Front Suspension                
4-Dr. 1993 4X2 Guenther   3.26      
4-Dr. 1993 4X2 Ford   4.1      
                 
4-Dr. 1993 4X4 Guenther   5.13      
                 
Chevrolet Blazer                
4-Dr. 1996 4X2 Guenther   4.29      
4-Dr. 1996 4X2 Guenther VRTC 5.10 1.13 3.92 6.28
4-Dr. 1996 4X2 Guenther Ford 4.15      
4-Dr. 1996 4X2 Ford   4.12      
4-Dr. 2001 4X2 VRTC   5.97 0.58 5.36 6.58
                 
Mercedes Benz ML320 - 4 Dr. 1998 4X4 Ford   2.7      
  1999 4X4 VRTC   3.05 0.18 2.86 3.24
  2000 4X4 Ford   2.5      
                 
Toyota 4Runner - 4-Dr. 1999 4X4 Ford   4.0      
  2000 4X4 Ford   3.6      
  2001 4X4 VRTC   3.64 0.47 3.15 4.13
                 
Ford Escape - 4-Dr. 2001 4X4 VRTC   4.21 0.13 4.07 4.35
  2001 4X4 Ford   2.50      

*  Firestone provided the raw test data for the vehicles tested prior to May 31, 2001, VRTC staff analyzed this data using the same data reduction techniques used for the tests performed by VRTC, and Ford staff analyzed the data for the Chevrolet Blazer and Jeep Cherokee using the same data reduction techniques used for the tests performed by Ford.

**  The Standard Deviation and the 95% Confidence Interval indicate the statistical variability of results obtained during individual test runs performed during one series of tests. For both the VRTC tests and the "Guenther" tests, there were three test runs in the clockwise direction and three test runs in the counter-clockwise direction.