Rob
I was following a Chevy Cavalier and I could have sworn it was moving sideways down the road. I don't mean it was skidding or anything like that but I could clearly see one side of the car more than the other. Was this an optical illusion or do I need medication?
Steve
Good thing I have an answer for you, Steve, because I don't want you to think that I can diagnose heath issues, so let's keep you off the meds.
What you have witnessed is commonly termed "Dog Tracking" or "Crabbing".
As the label implies, this is not unlike the way a dog trots or a crab walks - a little bit sideways. This is caused by a misalignment of the rear wheels on any given vehicle, and can be caused by bumping a curb while backing up or by driving through deep pot holes. This is easier than you think nowadays because cars are built lightweight and don't have the structural integrity of vehicles from days gone by.
In a perfect world the rear wheels are exactly parallel with the centre-line of the vehicle. This is critical as the rear wheels are used as the start point for a proper wheel alignment. You may have seen advertisements for four wheel alignments. This is not a come-on; this is a legit process that any reputable alignment shop will perform. They must set the rear wheels straight first because all the measurements and settings for the front wheels are based on the rear tracking straight.
If the rear wheels are skewed to the left, as an example, the rear of the car will want to angle or dog track to the left. This gives the appearance of the car going down the road sideways, just like a dog trots - with its rear end off to one side.
This has a very serious effect of the handling of the vehicle - not the least of which is turning a corner.
If the vehicle tracks to the left, each time the car makes a left-hand corner, its rear end will tend to under-steer. The back end will want to stay to the left as it is already "steering" in that direction. This means that the left rear tire will either cross the centre-line of the turn or if there happens to be a curb on the left side, the tire could possibly hit the curb, in essence, the back end will always try to cut the corner.
Turning to the right has the opposite effect. The rear will over-steer. The left "steering" back end will want to swing wide around every right hand turn. The driver should notice the fact that it takes more steering input to turn right than left because the steering wheel will have to counter the forces created at the back of the car not to mention that the trying to drive in a straight line will require the steering wheel to be offset to the left as well as a constant fight to keep the car in that straight line.
Any vehicle exhibiting these characteristics needs to get its rear end into an alignment shop sooner rather than later.