Valve stem locking nut corroded on left front wheel and separated from stem. The stem actually fell inside the wheel causing a blow out. No injuries, but this could have been serious at highway speeds. The defect happened at 45 months, and 51,000 miles. Subsequently all stems and sensors had to be replaced prior to 48 months. Per the tire dealer and grudgingly by Volvo, this is fairly common for that vintage of stem and sensor. Volvo did not honor warranty because the failure happened 1000 miles outside of mileage warranty but inside the 48 month timeframe, very poor service from a company that is supposedly known for safety. I find it ironic that a mandated safety feature barely lasts through the warranty period, and the failure mode causes the problem it was "designed" to prevent. Replacing the sensors cost about $150 each, or at least $600 for the life of the car.

- Troy, OH, USA