Tires: Alignment, wheel alignment, shocks and struts

Question
QUESTION: I'm getting an alignment because I replaced the shocks and struts on my car.  I brought up the hypothetical question with the guy at the front desk.  I have a 1995 VW Jetta.  If the rear wheels don't need any adjustments, what's the difference between a two wheel and four wheel alignment?  Everything they'll do is exactly the same.  The answer he gave me was, the rear wheels have adjustments, that's why it's a four wheel alignment.  I figured, if the rear wheels were in specification, and they did no adjustment, there's no reason I should pay the additional cost for a four wheel alignment.  Is this an unreasonable line of thinking?

ANSWER: Bruce,

The procedure for measuring the alignment involves setting up the equipment, then doing a measurement, then doing an adjustment.

So let me start by saying that EVERY corner of the vehicle CAN be adjusted.  It might involved the use of an eccentric bolt, or an adjustment plate, but also slotting a few holes or bend some metal, but toe and camber is not only measurable, but also adjustment is possible.

In the days where most rear axles were mounted firmly on leaf springs, it was unlikely that the rear axle would move relative to the frame.  But today's front wheel drives are not only sensitive to front end misalignment, the rear is also less rigid - but you get a better handling vehicle - but it is also more prone to misalignment - even if there isn't any provision for adjustment.

So if you have only the front end aligned, it is only relative to the frame.  If the rear end is out, you can get vehicles that "dog track", and that would cause tire wear problems.

So FWD (and AWD) really ought to have 4 wheel alignment and when the alignment shop says they CAN'T do an adjustment, tell them they are wrong and find another shop.

In other words, paying for only a front end alignment involves a risk.  And if you want to take the risk, then be aware that the price could be a bad handling car or the price of a set of tires.

---------- FOLLOW-UP ----------

QUESTION: You didn't address my question, which is, if the rear wheels are within specification, and the shop doesn't make any adjustments to the rear wheels, isn't that just a two-wheel alignment?

I'm not asking for a two wheel alignment.  I'm saying if they don't do the work for a four wheel alignment, why should I pay an additional cost for one?  They still have to mount the heads and measure them.  So if the rear is within specification and they just adjust the fronts, then it's only a two wheel alignment.


Answer
Bruce,

I'm sorry, but I thought my first sentence answered the question, but perhaps it could have been clearer.

The term "doing an alignment" means not only adjusting, but also the setup and the measurement.  So, no, if you measure the rear end and it is OK, then you've done a 4 wheel alignment.  Doing a 2 wheel alignment, means you don't know about the rear.