There are two important details that need to be considered. First, was the pull there before the new tires were installed? Second, it sounds like you may be making a very common mistake. Your mechanic said the car has a pull to the left, and you said the car "tended to pull over left with the steer wheel straight".
It sounds like the alignment is not right or you have a defective new tire. I would try rotating the tires front to back to see if that changes it.
A pull, often called a "drift", is when the car goes toward the ditch or on-coming traffic when you let go of the steering wheel. It has absolutely nothing to do with the position of the steering wheel. You can take the steering wheel off and throw it away, but the car should still go reasonably straight. Now, common sense comes into play, but it is not so common for car owners. That pull or lack of pull depends on a huge list of variables. One is the road you are on. Most roads lean to the right so rain runs off, and any car is going to follow that lean and pull to the right. We address that during the alignment by adjusting in a slight pull to the left to offset that "road crown". A road that affects one car will not affect a different car, so that is another variable. Next, all roads lean different amounts in different places. We can only adjust the alignment for the closest average and that is usually a good compromise.
The second condition is a crooked steering wheel. There can be different causes for that too, and they can be confusing at first. If you let go of the steering wheel at highway speed and the car goes straight for a good quarter mile, you do not have a pull. If the steering wheel is not centered at that time, you simply have an offset or crooked steering wheel. That is addressed with the alignment and is the last step in the procedure. There were some cars and trucks years ago on which after the alignment was finished, if the steering wheel was not centered, you were to physically unbolt it, remove it, then set it back on straight. Doing that did nothing to the alignment. It just made for a centered steering wheel.
Where the confusion comes in is when someone has a crooked steering wheel, and they put it straight, then the car steers to the side. Of course the car is going to go the way they turned the steering wheel, but that is not a pull. That is a crooked steering wheel. If you tell the mechanic you have a pull for that symptom, he is going to test drive and test drive trying to figure out what you are talking about so he can determine what to correct in the alignment. He will be working on the wrong thing.
You must also understand that each side of the car has an inner tie rod and an outer tie rod screwed together. They are screwed together more or less, similar to a turnbuckle on a screen door, to lengthen or shorten that linkage, and that sets the position that tire is steering. The last step of the alignment procedure is to lock the steering wheel perfectly straight, then adjust each pair of tie rod ends to make each wheel steer straight ahead. Those adjustments are very precise. When a tie rod is worn, it can allow that wheel to turn a little but it can be hard to notice at first. It will show up as a specific tire wear pattern long before you will notice the steering wander.
I have to be careful on how I describe this, but speaking in simplistic terms, a worn tie rod end will not cause a pull. For this sad example, lets say a left tie rod end is worn and you have a front-wheel-drive car. Typically what happens is when you accelerate, the left tire tugs forward and the sloppy tie rod end lets it turn a little to the right. Naturally the car is going to go to the right, so you have to turn the steering wheel to the left to counteract that. What you are doing is turning the right tire to the left a little. Both tires will be steering toward the center of the car equally, so the car will go straight. The symptom, if it is bad enough to even notice, is the steering wheel will be off-center to the left, but again, that is not a pull. The car is going straight, so it is not pulling.
Please let us know what you find. We are interested to see what it is.
Sunday, September 21st, 2014 AT 10:04 PM