1999 Grand Prix right front tire came to rest on the undercarriage and suspension. 5 lug studs snapped off.

- Waterford, MI, USA

Driving down the highway my 1999 Pontiac Grand Prix developed a low hum in the front end which fairly quickly - within 30 miles - escalated to a substantial rumble/roar. I then experienced a sudden and pronounced wobble. I pulled into the breakdown and eventually found that 4 of the 5 studs holding the right front wheel on were gone. The studs were sheared off down to the rotor. There was little in the way of warning. No change in driving characteristics in days prior to the incident. On the day of the incident, I did note a rotational 'ticking' sound, which I thought might be a stone caught in my treads. After driving for approximately 60 miles, I stopped for gas and checked: No stone. Leaving the station, I noted a faint thump, both heard and felt in the pedal, when braking but it did not seem like an acute situation. It was approximately 20 miles later that the failure manifested. I suspect this 'thumping' was because one or more studs had already failed and the wheel was now not secured properly. A repair shop said if the lugs had been loose, there would be a characteristic wear on the wheel. This was not present. This shop replaced the 4 sheared studs. Cartalk radio show hosts suggested over-torque as a possible cause, and suggested I get other lugs inspected immediately. I took the car to a tire shop. They inspected the remnants of the studs I had the other shop save. They indicated that in their experience, failure due to over torque leaves a characteristic pattern on the metal, which was not present. Inspection confirmed no pattern characteristic of loose lugs was present. They were not able to determine the torque on the other lugs on the other tires but doubted over torque as the cause. I have the remainders of the sheared studs avail for inspection and/or analysis. I am contemplating replacing all 15 remaining studs just for piece of mind. I will retain those parts should I have them replaced.

- Durham, NC, USA

Problem with right wheel studs breaking off. Problem occurred on two occasions, repair made at dealer. Please provide any further details on this matter.

- Cobb, CA, USA

Lugs:nuts and bolts sheared off the front right tire, causing front right hand side of the car to fall down on pavement. The wheel rolle dforward and struck another car.

- Lake Forest Park, WA, USA