Luxury SUVs
The Power to Stop
The amount of heat that brakes must dissipate is directly related to a vehicle’s weight, thus the brakes fitted to these heavyweight steeds face a tough mission. The FX50S was the lightest at 4643 pounds, the SRX came next at 4762 pounds, and the Cayenne S was the heavyweight, posting a brake-killing 5476 pounds.
The Porsche’s brakes, however, shrugged off the 2.75 tons with little effect. After 25 stops, we simply gave up because the pedal feel changed little (it grew just an inch), and the last stop, at 356 feet, was only 20 feet longer than the first. Clearly, the 90 seconds of cool-off time between runs was enough to keep the Cayenne’s brakes from overheating.
The SRX acquitted itself fairly well, considering it’s not as performance oriented as the two other SUVs. Although the disÂtances for the first nine panic stops were reasonable, ranging between 367 and 430 feet, things went downhill from there. After the 15th panic stop, the distance increased to 485 feet and the pedal lost its firmness, so we parked the vehicle.
The FX50S fared even worse. Not only did its brakes give up much sooner than those of the two other SUVs, they did so with little warning. Things were fine after the first six panic stops, with distances hovering around 340 feet. On the seventh stop (in the second test cycle), the pedal travel grew markedly longer and the distance increased to 432 feet. On the eighth, the pedal went to the metal. We held it there, and the Infinitigradually came to a stop in 473 feet. We tried a few more times, but the car was braking with only half its maximum capability even though we were pushing on the pedal with more than 100 pounds of force. Afterward, we discovered that the rotors were deeply grooved, too. We contacted Infiniti, and the company says it is investigating the problem.
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