Why Do cars "Go Out of Alignment"?

Everytime I buy a tire, they try to sell me a “front end alignment”-do cars actually drift out like that? As I understand it, the front wheels have three alignment angles: castor angle (the angle of the wheels from the vertical axis, camber angle (the deviation angle from the horizontal axis), and the tracking angle (the angle of the wheels WRT the steering box. These must be checked when components of the front end are changes, or if there has been front end damage, otherwise, they should be fixed for the life of the car. My Saturn SC@ staying in alignment for 120,000 miles-do some cars just "drift"out of alignment?

I don’t know why, but from a car I had in the 80’s (cheap, cheap and cheap - chose 2), it often was out of alinement when I drove over a few speed bumps. the crossover SUV I now drive seemed to hold it’s alinement for over 200K miles.

Go figure

  1. Frame geometry shifting, either from wear and tear or progressive bending under stress. Not too common except in lightly built and long-mileage cars, and those that take a real pounding over bumps.

  2. Suspension component changes - progressive bending of arms and links, wear on bushings and ball joints, etc. Pretty common especially on rough roads and lots of bumps and curbs.

1&2a) Any kind of accident can cause bends and twists in both the frame and suspension components. Very common, even from accidents that don’t cause much other evident damage. A few degrees twist or bend is enough to screw things up.

  1. Suspension adjustment changes. There are usually lock nuts and cotter pins on everything that can be adjusted, but some initial looseness can result in slow changes of the geometry.

  2. Tire wear and tire changes. Some aspects of alignment are dependent on the exact geometry of how the carcass and tread relate to the road under vehicle loading. Not too common unless you go from one tire extreme to another. (Such as a very rounded profile to a slightly larger, square-edged profile.)

Some vehicles are much more durable in this regard; I can’t remember the last time I had a vehicle more than slightly out of trim, even after many 10k’s of mileage. Others drift out of alignment on the drive home. cough Lotus cough Jaguar cough

Honda’s wishbones will bend if you look at them funny. :slight_smile:

Potholes and curbs.

Wonder how hard it would be to make a car self-aligning.

Used to be that only Volkswagen beetles needed four-wheel alignments. Now it appears that everything front-wheel drive, four-wheel drive and all-wheel drive needs four-wheel alignment$.

What’s the worse that could happen if you skip the alignment? (and the car drives reasonably straight down the highway, so the parts are reasonably close to being in alignment)

I’m thinking maybe slightly faster or uneven tire wear. The trouble is, replacing a couple tires is only $130 where I’m at. If you had to replace the tires 6 months sooner, and the tires normally would last 5 years, then that’s about $13 in “value” lost from the tires.

The alignment fee has to be more than $13…

The problem is that if the alignment is more than a little off you get WAY faster and uneven tire wear. I think I had the same kind of Honda as randompattern did and if you didn’t check the alignment when you got tires, by the time you got the first rotation the front tires would be completely bald on the edges. Yeah, it was probably a wash cost wise, but if you drive in bad weather having the front tires going bald almost instantly really isn’t acceptable.

That was a nice car otherwise, though!