Help (!)

[vonVeezelsnider]

So I drove the Cobalt out this morning to run some errands for my Grandmother and all was well with the car, then this evening I ran out to get some pizza and as I pulled onto the expressway the car started shaking badly above about 60kph (40mph for the Yanks). At first I thought I had a flat tire so I pulled off at the next exit and examined the car, checked the tire pressure as well as the rims and nothing seemed out of place. There's no snow/ice in the wheel wells making contact with any of the wheels either. I got on the expressway again and it started again at the same speed. At first I thought it could be the road surface but I'd driven on the same road three times previous during the day and this didn't happen. I can feel the shaking/pulsing through the floor, my seat, and the steering wheel and it seems to be more pronounced on the drivers side than the passenger side.

I've never seen this before but I'm wondering whether it's something wrong with the car (suspension bushings/bearings/what have you) or the tires/rims (slipped belt). Obviously if it's a defect with the car warranty will cover it but if not I guess I'm on my own.

In the interests of full disclosure I haven't hit any curbs/potholes etc or given the car a reason to do this.

[SAmadei]

In the interests of full disclosure I haven't hit any curbs/potholes etc or given the car a reason to do this.

Even though you didn't hit nasty potholes or curbs, you might have lost a wheel weight... especially if you have stick-on wheel weights. Ensuring your wheels are balanced is the first step.

Did you drive through any sticky mud? Sometimes that can stick the rim and case an imbalance.

Most suspension problems would have come on slowly... anything that happens fast in the suspension world is usually catastrophic failure... and you would know exactly the problem.

Also, try revving the car to about 3 grand and feel for a similar vibration. Another though would be to jack up the front, and put the car on jackstands and run it at 40 mph... this will help isolate if it is a drivetrain problem or a front wheel problem or a rear wheel problem.

[vonVeezelsnider]

Even though you didn't hit nasty potholes or curbs, you might have lost a wheel weight... especially if you have stick-on wheel weights. Ensuring your wheels are balanced is the first step.

Did you drive through any sticky mud? Sometimes that can stick the rim and case an imbalance.

Most suspension problems would have come on slowly... anything that happens fast in the suspension world is usually catastrophic failure... and you would know exactly the problem.

Also, try revving the car to about 3 grand and feel for a similar vibration. Another though would be to jack up the front, and put the car on jackstands and run it at 40 mph... this will help isolate if it is a drivetrain problem or a front wheel problem or a rear wheel problem.

There's lots of slush and snow on the ground up here but that was one of the first things I checked and all rims are clear inside and free of obstructions as for mud- it long since froze at minus twenty-five temperatures.

It was dark out but it looked like the wheel weights were attached. I'll check again come morning.

Edited December 11, 2009 by vonVeezelsnider

[Intrepidation]

Sounds like either the wheel(s) are out of balance or the tires have improperly worn. I'd be inclined to go with the former if they've been fine until today. Have the tires checked and the wheels rebalanced (which is inexpensive) and go from there.