With the end of snow season comes the time to dump the snow tires and put on the summer ones. It's also time to have that annual wheel alignment done on your vehicle. Just be careful so that you don't have the same problems as a friend of mine had.
He had the shop install some newer tires, which were already mounted on rims, before the wheel alignment was done. One of the tires was quite low on air but he thought that they would check the tire pressures before starting the alignment. They didn't. The tires were inflated to the right pressure afterwards and now the car pulled to one side. The shop was contacted but he was ensured that tire pressure wouldn't affect the alignment. He didn't believe it and neither should you.
For any alignment shop to align the wheels without first checking the tire pressures in the belief that it doesn't matter is odd. One of the first signs that a driver has that the tires are low is by noticing that one side of the car is lower than the other and ,in many cases, that the car pulls to one side. This is because a car behaves much like a cone as it rolls down the road - it wants to turn toward the side or end which is the lowest or smallest.
There are several preliminary checks which should be made before doing a wheel alignment including adjusting tire pressures, checking for broken or sagged springs, checking for any excess weight in the trunk, making sure that the tire sizes on each end of the car match and many other little 'hidden' details. Sometimes it even helps to notice the driver's weight - heavier drivers sag the car down more than normal. Failure to compensate for, or repair, these simple items will lead to a faulty alignment.
The two major angles which affect steering control - caster and camber - are set relative to the level ground. Camber tilts the top of the wheel inward or outward. Caster moves the upper part of the spindle (the thing that holds the wheel upright) forward or backward. Theoretically, the car body and frame can sit at an angle and the wheel alignment can be done. The car won't pull or wander but it won't 'look' right either. The car is crooked but the wheels are straight. This is what happened to his car - until he upset everything by correcting the tire pressures. Now the car pulls because the car is straight and the wheels are crooked. It's like walking with a high heel on one foot and a slipper on the other.
Many wheel alignment shops are only concerned that the car doesn't pull one way or the other when it leaves the shop. That tires might wear quicker doesn't matter because the tires wear so slowly nowadays anyway unless alignment is very poor.
The only thing to do is to take the car back to the alignment shop and explain the problem and ask them, nicely, to redo the alignment - free of charge. If that doesn't work create a big fuss until you do get a free alignment. I don't think that it's up to you to tell them to check tire pressures and other things to be wary of before they start the job.
A proper wheel alignment is a complex job which can only be done by properly trained technicians who care enough to do a good job. Cars with four wheel independent suspension where a '4 wheel alignment' is required are even more critical. All the fancy computerized gadgetry in the world is useless if the person doing the job forgets the little details. As with any computer, its only as good as the person running it. I think too many shops rush the jobs or use untrained help to maximize profits. Unfortunately it's the customer who gets the big bill and the bad bill of goods. The only way to stop this nonsense is to complain loudly, walk into the shops prepared to do battle and give the impression that you know what you're talking about.