If they realign it, ask for a copy of the printout. I always kept one for my reference and I always put one on the passenger side of the front seat with the numbers highlighted that I adjusted.
The I-beam suspension is strong but it is not good for tire wear. The twin I-beam is a compromise to improve ride quality but it is by far the worst suspension design for tire wear and adjusting out a pull, especially when it is put under skinny trucks like the Bronco 2. Watch how severely the front tires tip out on top when one of those is raised off the ground. That's what the tires do as the truck bounces up and down going down the road. There are no easy camber or caster adjustments. Those are the two angles that affect pulling to one side when you let go of the steering wheel. Ford has always had problems with their alignment adjustments except on a few older rear-wheel-drive cars. It has always been up to the aftermarket industry to come up with fixes to correct alignment problems. In your case there are steel inserts in the knuckles that the upper ball joint studs go into. You can buy those with offset tapered holes to move that ball joint forward, rearward, left, or right, or a combination of those.
Camber is the inward or outward tilt of the wheel as viewed from in front. Tires want to roll in the direction they're leaning, and if they're leaning excessively they will run on the edge of the tread causing it to wear faster. Both wheels must be in specs for the least tire wear, and they must be equal to offset any pull. Those offset bushings allow for some correction but the cause most often is sagged springs and incorrect ride height. That should be checked first when there's a tire wear or pulling problem, then the truck should be aligned. If camber is still off when ride height is correct it is due to a fatigued or bent I-beam. In your case production tolerances can result in the need for an offset bushing when the I-beam is replaced. It is rare to replace the I-beam and have it end up in perfect alignment the first time.
It is also always possible someone installed an offset bushing years earlier without checking and correcting ride height first. When the springs are replaced later those offset bushings will have to be removed and standard ones installed. There's two problems with using these bushings. First of all, only tire and alignment shops stock the multitude of sizes and styles. There are so many that the cost to stock all of them just in case you might need one a few times a year doesn't make sense. Instead, the mechanic has to put the truck on the alignment machine, set up all the equipment which can be quite time-consuming, take the measurements to find out how much correction is needed, then he has to take the old bushing out, (which can be a huge job if they're rusty or impacted with dirt), hope that he can see some numbers on it to tell if it is already an offset bushing, then he has to calculate how much more or less the replacement bushing has to be offset, order it from a local parts store and hope they have it in stock. All the while he's waiting for it to be delivered that hoist and computer are tied up and can't be used for another job. If the bushing has to be special-ordered he either has to put the truck back together, put it outside, and start all over tomorrow, or he has to work around it on other vehicles the rest of the day.
That second problem is he won't know if there is already an offset bushing in there. If he can't read any numbers on it, he has to get the old one out, install a standard one, set up the equipment again, take the readings, ... Again, calculate the bushing that is needed, ... Again, then order what is needed. A one-hour alignment can easily turn into an all-day job, and you may not even notice the results. All alignment mechanics have to go by what they consider "good enough". If the numbers show there is going to be a slight pull one way, they could easily adjust that on most other trucks, but unless that pull is really bad the time, expense, sweat, and skinned knuckles will likely not be worth the effort, especially when that pull could go away or get worse in the future as the springs continue to sag.
It is also common to not get the amount of correction you expected from the bushing you installed. There's a few other factors that play into how much any bushing will change the readings. You could move a wheel too much and make the truck pull the other way.
There is a third problem with these bushings. There's only one per wheel and changing it can change camber OR caster, depending on the position it is installed. That is easy to calculate. If you have two degrees with a standard bushing and you need 3 1/2 degrees to match the other side, you'd order a bushing with a 1 1/2 degree offset. The problem is that bushing can be rotated to any position midway so it changes camber AND caster. As an example, if you need to increase camber by 3/4 degree and caster by 3/4 degree, you might need a 1 1/8 degree offset bushing to accomplish that. There are all kinds of charts that look like multiplication tables to tell you the right bushing but they assume you're starting with a non-offset one, and those charts are almost always wrong. It ends up being a tedious and time-consuming trial and error project.
I shared all of that to explain why the mechanic may have left the truck with a slight pull. If you drive ten other Ford trucks you will typically find half of them also have a pull. It depends on how much you're willing to put up with and how much you're willing to spend to correct it. For a very slight pull, especially if the alignment is right, you can try switching the two front tires side-to-side. It is common for even new ones to have slightly different characteristics. Switching them could make the pull worse or it could go away.
The old tires should not affect the alignment unless they had different diameters. Different tread patterns can cause a pull due to different rolling resistances but all that's important on the alignment machine is the truck sits level. That is not even a requirement on some of the new computers. The hoist doesn't even have to be level, just stable and not rocking. I preferred to align vehicles with the old tires so I could "read" their wear patterns to be sure I found everything that needed correcting.
Wednesday, May 1st, 2013 AT 10:03 PM