Jeep Moose Test: Roll Over Mitigation Gone Wrong

Roll-over mitigation is nothing more than a yaw sensor mounted on its side. It measures the amount and rate of roll along the vehicles horizontal axis. What is amazing is the programming that takes the information and turns it into corrections performed by the brakes through the hydraulic control unit.

Teknikens Värld is like the Consumer Reports of Sweden and when they test cars they perform the moose test where a vehicle has to perform a sudden lane change and panic stop to avoid a moose. When they performed the test on the Jeep Cherokee they had some alarming results

“The car was tested in the same way as thousands of other cars have been tested by Teknikens Värld over the years. Loaded (driver, passenger and anchored sandbags with a low center of gravity in the boot) in accordance to Jeep’s specifications for maximum payload, the factory installed original tires filled with the amount of air pressure as specified by Jeep (also confirmed by Jeep/Chrysler) and all safety systems such as electronic stability control and anti-rollover system turned on. Jeep Grand Cherokee has air suspension and we put this in Auto mode, a setting that most Grand Cherokee owners use when they drive their car.”

While the Jeep never rolled, it was very unstable and managed to blowout the tire on the left front six times. Looking at the design of the vehicle it does not differ that dramatically from the VW and Volvo they tested.

In my estimate, the problem here is the ESC and roll-over mitigation system software. The roll-over mitigation would decrease the hydraulic pressure to the wheel that has the most weight loaded on it. In the case of the Jeep, it would be the right front and then the left front during the maneuver. The braking force is then transfered to the other wheels.

But, it appears the calibration for the Jeep is a little off. The good news is that this can be corrected with software and not mechanical parts.

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