Toronto S5

Hi guys, the other day I was driving on the highway when all of a sudden I felt like one of my tires (couldn't tell which) was hitting a bump... except the roads were completely paved and had no potholes. Every few revolutions it just felt like one of the tires was hitting something.

So naturally, I checked to see if it was a flat at a gas station. A guy there said it wasn't (we checked all the tires, none were flat), but he suggested that something on one of the wheels that balances the wheel may have come off, which created an unbalanced wheel and may have made this happen.

I noticed that it wasn't happening all the time... only sometimes. The guy at the gas station (by no means an expert) asked if this was only happening at 110 km/h or so and I said "hmm... maybe". Because it wasn't always happening at slow speeds but felt like it was on the highway. When I drove on local roads later I didn't feel the issue at all.

Is he possibly right? Could it be anything else? I guess I should bring it in anyway unless anyone tells me it's nothing... thanks.

ChipB

If you lost one of the wheel weights you could experience a "thumping" vibration that varies with the speed of the car. Often if this happens to one of the front wheels you may feel the vibration in the steering wheel as well. The thumping will typically be worse at some speeds than others - it will be worse at speeds that cause the tire to rotate at a multiple of the natural frequency of vibration of the suspension.

Another cause could be having a rock stuck in the tread or rim - so inspect the treads.

First you should verify that the thumping varies with speed of the car, and speed of the engine. If it does, then I suggest taking your car to a local tire shop and have them rebalance all 4 wheels. That will probably fix the problem.