Earlier this week, the Swedish consumer magazine Teknikens Värld revealed that the Jeep Grand Cherokee nearly rolled over in their "moose test." While the magazine and automaker debate the testing particulars, with the latter involved in some damage control public relations, our engineers explore what this means for U.S. consumers.
The European moose test is a double lane change maneuver that simulates an emergency situation, requiring a quick steer to avoid an obstacle and then turning back into the travel lane to avoid an oncoming vehicle. According to Teknikens Värld, in every run performed with the Grand Cherokee, the vehicle either went up onto two wheels or debeaded tires (separating the rubber from the wheels) thereby posing the risk of a tripped rollover.
Chrysler's corporate press release states that the test is "invalid" because the vehicle was overloaded beyond its stated load capacity. A separate blog on a Chrysler website says it was overloaded by 110 pounds.
After the results were revealed, Chrysler engineers met with the magazine, providing three Grand Cherokees for a re-test. For subsequent tests, the Chrysler engineers witnessed that vehicle was properly loaded. While no other instances of two-wheel lift occurred, the magazine states that the tires were also debeaded in these runs. (Read: "Jeep Grand Cherokee's moose test failure—truth and facts.")
Consumer Reports tests the emergency handling of all vehicles in our own double lane change maneuver, which is similar in concept. Our test is less severe than the "moose test" with more distance between the entry cones and the gate cones, typically resulting in less steering input. Plus, we test the vehicle loaded with only a driver and a full fuel tank.
We have tested two 2011 Grand Cherokees, a Laredo with the V6 and a Limited with the V8. Both had 18-inch wheels and tires. During our initial tests, the Laredo V6 hopped and skipped sideways. While it did not debead tires or go up on two wheels, this behavior did impair driver confidence and affected the speed at which we could negotiate the course. The Limited V8 did not exhibit this behavior.
After that test, Chrysler recalibrated the stability control and issued a software update in January 2011. The software changes eliminated the problems we encountered and increased the speed and confidence through the course. This update was flashed into existing vehicles and incorporated into later-production Grand Cherokees.
Our experience with the Jeep, as well as the hundreds of other SUVs we've tested, shows that the way the vehicle is equipped can have a considerable effect on its performance in this test. Tire specifications, suspension calibrations, and weight balance all play a role here. The Grand Cherokee tested by Teknikens Värld was a top-level Overland 3.0 CRD V6 (diesel) model with 20-inch tires that comes with adjustable suspension. (The diesel is not currently sold in the U.S. market; engine selection will affect weight balance.)
Loading is a point of contention in this moose test since it was run with five occupants on board and sandbags in the cargo area. While Chrysler states that the Jeep was overloaded by 110 pounds—about 7-10 percent of the payload rating—Teknikens Värld states the vehicle was weighted appropriately according to the Swedish registration certificate. Individual vehicles can have different payload ratings because of variances in optional equipment, which may be different from weights listed in compliance paperwork. Regardless, it could be argued that overloading it by 110 pounds falls within the realm of foreseeable misuse by a consumer and such a variance should be accounted for in vehicle development.
So what should a consumer here in North America take away from this test?
As a class, SUVs are more top-heavy than cars and are more prone to rollovers. As good as modern stability control and chassis design often is, there is no way to change the laws of physics. But it is worrisome that other SUVs tested by the Swedish magazine, including the Volvo XC90 and Volkswagen Touareg, did not have any problems in this test.
Despite the war of the words that is ongoing, we wouldn't be surprised if Jeep would change the electronic stability control (ESC) calibrations on the Grand Cherokee going forward to improve their performance in this test and possibly adjust the recommended weight limits. Teknikens Värld states that there was almost no engagement of the ESC in their tests. That's a surprise, since the moose test has been around for over 40 years. You would expect passing that test to be part of vehicle development criteria, just as passing CR's avoidance maneuver test is an engineering priority for many automakers.
The Jeep tested in Sweden differs in equipment from models that have been tested by CR and the National Highway Traffic Safety Administration (NHTSA) in their dynamic stability testing.
While no vehicle should be operated while overloaded, staying within the limits is crucial for SUVs. Be especially cautious about loading heavy items on the roof.
We hope that Chrysler and Teknikens Värld get to the bottom of why the Grand Cherokee failed the moose test, because no modern vehicle should perform as shown in the magazine's video.