Come on. You know we need more details than that. You could have air turbulence from the sunroof, the tires are bald and you're hydroplaning, a broken tire belt, collapsed engine mount.
Do you feel this in the steering wheel? In the seat? Only when accelerating? Did this start suddenly or get worse over time?
June, 17, 2012 AT 5:21 AM
I feel it in the steering wheel, it is not when accelerating.
It is felt mostly on curves and over very small road bumps. Also I feel it after driving the car for more than 15 minutes.
June, 17, 2012 AT 5:43 AM
That would be typical of a broken belt in a tire and is more likely to occur when it has worn to the point that you can justify replacing it. Start with a visual inspection of both front tires. This can be hard to find with the car on the ground but not impossible. Suspension and alignment specialists will raise the vehicle up and spin the wheels by hand while watching the tread pattern from in front. If you see what looks like a tumor in one spot on one side of the tread, that's a broken belt. Sometimes you can feel the lump by sliding your hand around the tread but you have to be careful. Very often a belt breaks when the tread is almost all worn away and the wires of the steel belts will poke through. It really smarts if you snag one of those in your finger. I always gently pat my way around the tire first, and if I don't get poked, THEN I slide my hands over the tread.
Another way to identify a broken belt is by watching the steering wheel while you drive slowly through a parking lot. A belt separation will cause the steering wheel to move left and right a little with each tire revolution. When the broken belt is on the rear you'll feel it by the seat moving left and right.
There is a less common and more subtle way to have a broken tire belt that a lot of mechanics don't know how to check for. You have to run the engine in gear with the vehicle jacked up, then watch the surfaces of the grooves in the tread. If those grooves have a definite high and low spot, the belts are broken. When that happens gradually over a long period of time, the hump that develops wears away from driving on it, and the only evidence is in those grooves. The belt separation causes a weak spot that lets that axle and corner of the vehicle drop down a little each tire revolution and that's what you feel and what the steering wheel is reacting to.
Broken belts often occur on newer tires that had a hole that needed to be repaired. Most tire shops take the tire off the wheel and glue on a patch. That was always the best repair but it leaves the hole there that water, dirt, and road salt can get into. That corrodes the wires of the belt leading to it breaking. Some mechanics install a plug to seal the hole, then they glue on the patch to seal in the air. The plugs available today are pretty good but they are not recommended for fixing holes near the edge of the tread by the sidewalls. There's too much flexing and the thinking is that will lead to them working loose.