Alignment facts

Some simple truths about what alignments can can't do

My front end bounces, I need an alignment. No you have a tire problem, fix that first then see how the alignment is. Bounces or shimmy's are almost always a balance or out of round tire. The rotational force is causing the tire to go up and down or side to side. Tire balance and bad shocks eat a lot more tires than people think. Just because a shock isn't leaking doesn't mean its not dead. If yours are more 24 months or 200,000 miles on the steer really think about changing them.

"I have a knocking sound in my steering do I need kingpins?" If the kingpins are that worn you will probably need more than just pins and bushings. I have seen the axle destroyed from loose pins.

If you have a truck with greaseable shackles they may be the knocking you hear when you turn. The springs with rubber bushing in the ends almost never make noise. If they do it's usually a sign for repair.

But here's another thing often overlooked that causes that. The steering shaft. If you have a non-greaseable shaft it can lockup at the slip yoke and cause a knocking sound and funky steering problems as the sector box gets hammered with the shaft physically popping up and down. What happens is the shaft telescopes in and out as it turns and when its locked up it forces that pressure onto the poppet valves in the box. The repair is to replace the shaft. This is another reason you don't want loose U-joints in the sector shaft because that play can get rebounded into the box and then truck starts to wander back and forth.

 

Axle setback, what it is and why is it important.

The steer axle needs to be as close to perpendicular as possible to the frame. That means it needs to at 90 degrees or as close as possible to 90 degrees. The amount its off is called setback. It can be either positive or negative as viewed from the drivers side. Negative is back from centered and positive is ahead of center. Neg turns you left and pos turns you right.

Ever seen a tractor dogtrack and wonder why? Many people think its always the drive tandems. Few people think about the steer that way but here's some simple math, .03 of a degree (3/100 of a degree) is almost 1/32 of an inch. Most alignment machine companies list setback as a non-adjustable setting. To adjust it you loosen the axle u-bolts and push or pull the axle to where you need it to be. It doesn't sound precise but a little practice with a porta-power and a come-along and you can get good results everytime.

Back to the math...I generally let any setback below .25 go (pos or neg) unless there's some other problems. The math at .25 is 8/32 or 1/4 of an inch. That tape measure findable measurements. Here's a dead giveaway setback has created a problem. The pitman arm position. It is supposed to be vertical when the tires are pointed straight ahead. If the bottom is leaning forward the axle is forward and the steering wheel won't be centered. If the bottom of the arm is towards the back then the axle is towards the rear and needs to come forward. When I open the hood I look at that arm and then the position of the steering wheel. If the arm is centered and the wheel is ####ed one way or the other the wheel or shaft is installed wrong. I need to add one thing here, this only works on a swingset style box. That means the pitman arm swings back and forth from the front to the rear. That does cover almost all trucks seen here in the states with one single tierod. Rack and Pinion is a whole other can of worms....

 

PLace holder number 2

 

Not a problem I see way to many guys get hosed on "needed" alignments. To be honest I wouldn't even say much but those jobs are usually accompanied by lots of bad tire wear. I've had my share of screwups ( we had a real machine problem) a year ago. It was a learning experience I never want to repeat.

The biggest thing I learned from last years mess was this, check the machines calibration and check it often! We check ours once a week and get it re-cal'd about every 6 months or when it needs it. Good procedures insure good results.

So when you go into whoevers shop ask when they checked for calibration before they do the work. If the answer is we don't need to, thats a brake check right there.

 

Well lets talk about shocks. A shock is there to dampen spring movement. That means it slows down the rebound mostly. Lets leave car shocks out of this.

On a big truck the weight will drive the wheel and that spring up and down as it wants to. What the shock does is slow down the repetitive high speed up and down. Most big truck shocks are valved at a 50/50 setting meaning they should have the same effect going in or out.

If you have river wear or a heel toe wear pattern on a free rolling axle (non-driving) you check 3 things first. Air pressure in tire, tire balance, and shock condition. The driver can do 2 of these 3 himself. Air pressure is easy, and shocks are easy too, is the shock leaking oil, are the mounting bushings worn out, and are the shocks working going down the road.

So look at the shock is it covered in oil, if yes then its junk. Grab the shock and see if it moves around on its mounting bolts, if it does then its probably junk but needs to be fixed. And 3rd drive the truck about 20 miles and grab the BASE of the shock just above the mounting point with a bare hand. It should be warm. If its not warm then the shock is dead and needs to be replaced.

I started this thread to give someone out there the info they need to be profitable. Not every driver is a mechanic. But some basic knowledge will save you some money and hopefully a lot of downtime.