How Tires Change a SUV’s Performance in Fishhook and Sine-with-Dwell Testing, Paper Number 09-0532, 21st ESV Conference, Stuttgart, Germany, June 2009. Arndt, Mark W., Rosenfield, Michael, Arndt, Stephen M.

A 2004 Chevrolet Tahoe was tested with the Original Equipment Manufacturer’s (OEM) base and optional recommended tires and wheels, and two sets of different sized aftermarket tires and wheels.  One aftermarket tire and wheel set used a much larger and wider rim with a low profile tire that did not significantly change the vehicle’s Static Stability Factor (SSF).  The second aftermarket tire and wheel set used the larger optional OEM rim with a larger than recommended Light Truck (LT) designated tire that significantly lowered the vehicle’s SSF.  Tests were performed pursuant to the protocols described in the United States Department of Transportation (USDOT) National Highway Traffic Safety Administration (NHTSA) New Car Assessment Program’s (NCAP) fishhook and sine-with-dwell maneuvers.  Results demonstrated that changes in vehicle performance due to the use of aftermarket tires were dramatic.  The lower profile tire and wheel combination produced vehicle tip-up in fishhook testing at 40 and 35 mph with and without ESC enabled respectively.  The larger LT tire and wheel combination did not produce vehicle tip-up in fishhook testing with ESC enabled, but did at 45 mph with ESC disabled.  Both base and optional OEM tires produced test results which fell in between the two aftermarket tires.  The vehicle successfully completed the sine-with-dwell test maneuvers with ESC enabled and failed with ESC disabled when equipped with either the base or optional OEM tires.

Effectiveness of ElectronicStability Control on Maintaining Yaw Stability When an SUV Has a Rear Tire Tread Separation, 2009 SAE World Congress, April 2009 Detroit, Michigan, Paper No. 2009-01-0436 Arndt, Mark W., Rosenfield, Michael, Arndt, Stephen M.

Electronic Stability Control (ESC) has the potential of improving yaw stability and reducing the occurrence of a crash when a vehicle experiences a rear tire tread separation. Two instrumented 4-door, RWD SUV's equipped with ESC were tested to evaluate the effectiveness of their ESC systems on maintaining yaw stability under these circumstances. The test vehicles were evaluated with the tread and outer steel belt removed from the right rear tire. Tests were run with the ESC engaged and then repeated with the ESC disengaged. All runs were completed with the tires inflated to the manufacturer's recommended pressure. An analysis of the data collected shows that there are significant differences in the steering input required to generate a loss of control response with and without ESC enabled. Results of Sine with Dwell testing demonstrate a significant reduction in vehicle spinout response with the ESC engaged. Over three times more steering input was required before the vehicle exhibited a spinout response with ESC enabled when compared to the ESC disabled vehicle. This will likely have a positive effect on a driver’s ability to maintain control when faced with a rear tire tread separation under real world circumstances.

Test Results: Ford PCM Downloads Compared to Instrumented Vehicle Response in High Slip Angle Turning and Other Dynamic Maneuvers, 2009 SAE World Congress, April 2009 Detroit, Michigan, Paper No. 2009-01-0882 Arndt, Mark W., Rosenfield, Michael, Stevens, Don, and Arndt, Stephen M.

An instrumented 2005 Ford Explorer was used to evaluate speed data provided from its Powertrain Control Module (PCM) at high slip angles. PCM speed was compared to speed and slip angle collected from a calibrated Datron S-400 velocity sensor. In addition to speed, slip angle and other standard handling test measurements the vehicle brake switch and throttle were recorded so PCM data could be synchronized. After each test run the vehicle ignition was turned off and the PCM was downloaded using commercially available Bosch hardware and software. The principal maneuver was the National Highway Traffic Safety Administration (NHTSA) sine-with-dwell test consisting of a 0.7 HZ sinusoidal steer with a 0.5 second dwell at the steer reversal peak. Runs were conducted with the vehicle's Electronic Stability Control (ESC) disengaged so that the test vehicle would achieve large slip angles. Other dynamic maneuvers included: NHTSA's sine-with-dwell with ESC engaged; 100% accelerator to 80 mph with 0.5G braking to stop; and acceleration to 50 mph with maximum ABS braking to stop. Results demonstrate agreement between the speed recorded by the calibrated instrumentation and speed recorded by the vehicle's PCM for conditions when the vehicle slip angle and rear wheel slip were near zero. PCM speed was lower than instrumented speed in high slip angle maneuvers. PCM on average under-reported during maximum ABS braking and at medium to high speed in 0.5G braking. In acceleration the PCM speed had no detectable under-reporting error except at the highest speeds with accelerator at 100%.