Why do vehicles need wheel alignment?

[steppinthrax]

I know it sounds like a dumb question. But my thinking is the only way a vehicle gets out of align is if a suspension/frame component gets damaged? But that usually is not the reason.

Assuming everything is within tolerance with suspension components, what actually causes the misalignment?

 

[SparkyJJO]

The bolts move.

Alignment is set by adjusting the control arms etc via bolts through slotted holes. If you hit enough potholes you can shimmy those enough to cause misalignment.

Anytime you get the suspension worked on you need to get it realigned (ball joints, bushings, etc).

And sometimes, yes, an arm or bracket can get bent. Sometimes it can be compensated for via normal alignment, other times the part needs replaced.

 

[Pacfanweb]

^Pretty good.

Things change. A suspension has moving components. The car is always bouncing on the suspension. That can make things move. Plus, cars hit potholes, curbs, etc....these things cause changes also.

 

[maluckey]

Not to mention springs settle, and sometimes sag, stiff rubber bushings get worn, struts and shocks age etc.

Granted, you could replace all the parts as they wear, avoid potholes and only drive where the roads are like pool tables....and never have to algn your car again.

I dream this way from time to time after going though a few contruction zones to make me feel better about the next alignment, where I wait for some kid to hopefully care enough to actually care about reading the manual on the 50,000 dollar Hunter alignment rack and computer to do the job right. It's this OR string it and loose two and half hours of my life that I'll never get back. Yeah...I hate alignment time.

 

[leper84]

I'd also guess unibodies and frames slightly flex over time. Not unreasonable to think 3000-9000lbs of aluminum and steel won't stay lined up to .1-.5 of a degree over years of abuse.

I have frequently wondered what the hell GM has done to their trucks to make them loose alignment so exceptionally fast.

 

[Zenmervolt]

Granted, you could replace all the parts as they wear, avoid potholes and only drive where the roads are like pool tables....and never have to algn your car again.

Nope, you'd need to align your car every time you replaced a part because there are small variations in hub location based on how everything gets bolted up/torqued down.

Strut replaced? You need an alignment.
New bushings? Alignment.
New tie rods? Alignment.



ZV

 

[Bartman39]

I'd also guess unibodies and frames slightly flex over time. Not unreasonable to think 3000-9000lbs of aluminum and steel won't stay lined up to .1-.5 of a degree over years of abuse.

I have frequently wondered what the hell GM has done to their trucks to make them loose alignment so exceptionally fast.

From the factory GM trucks are just base set but after the front end settles (approx 5K-10K miles) tires rotated then it should be aligned to proper spec's and it will hold just fine... But the alignment should be checked with every new set of tires to make sure nothing is causing an issue... This mainly applies to 1/2 ton trucks (including Suburban & Tahoe) the 3/4 ton reg and HD series and 1 ton trucks do not seem to have this issue and would suggest the cause is the softer front springs on the 1/2 ton trucks... 2500HD & 3500 trucks use torsion bars from 2000 to now if memory serves...? (might have changed at some point...?)

 

[phucheneh]

'Settling' is about the only valid reason, in my mind. Besides the fact that factory alignments are often not perfect, bolts sometimes don't get torqued properly, ect.

Torque is mainly a problem with adjustments that use cammed/eccentric bolts. I've seen a lot of instances that I suspected were due to the bolts gradually rotating into a preferred 'rest position.' Has almost always involved rear camber being maxed out, often on cars that haven't been touched since they left the assembly line.

But needing front toe set (a.k.a. all that most shops do on a modern car when they sell a 'four wheel alignment') because you hit some bumps? No.

I think the frequency with which alignments are typically recommended is another remnant days gone by. People still basing things off of the behavior of older cars...with sloppier steering, more (and larger) rubber bushings to provide places for gradual wear, ect. Your typical newer sedan/hatchback/ect just doesn't need it as much. Not to mention that most of them only have provisions to adjust front toe. Possibly rear toe and camber, but even with IRS, there are sometimes no adjustments to made. Aside from tweaking the position of an entire rear subframe, or other 'most shops will never bother with this' tricks like that.

Most tire wear that is attributed to a 'bad alignment' is more the result of improper inflation, infrequent rotation, and sometimes just shoddy-ass tires. On a related note, a lot of claimed alignments issues (pulling) end up being from tires. Helpful hint: if there are no front camber/caster adjustments, an alignment will do absolutely nothing for a true 'pull.'

Adjusting toe will help center a steering wheel, but that's all- it will never cause a car to pull. No matter how far out of spec it is, it will always equalize once you start going down the road. E.g: with the wheel straight, you have 0* on one side, and .5* toe-in on the other side. Total toe...half a degree. Divide by two. Each wheel will be toed in .25*, with the steering wheel pointing to one side. But the car won't be trying to turn on its own.

 

[steppinthrax]

As a vehicle ages, does it need alignment less often, or the misalignment are less severe. I'm assuming a new vehicle gets out of alignment in the highest amounts during the first 60 - 100K?