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Truck Topics
The Importance of Alignment
By Gene Dunlap
May 13, 2009 - 8:32:32 AM


When is the best time to align a truck? Many would say when you put new tires on. Actually, alignment should be checked before the new tires are installed. By looking at and feeling the old tires, the technician should be able to know what the truck is doing, and then by talking with the driver, confirm what the tires are saying. 

Does the truck pull to the right or to the left? Many drivers are so accustomed to steering right or left that they do it unconsciously and are unaware of the cause and the amount of energy consumed and wasted. They may think that it is normal to steer one direction or the other. Does it wander or is there a vibration? If it vibrates, at what speed? If the vibration is at less than sixty it’s probably alignment; over sixty it’s balance. Where do you feel the vibration, the steering wheel or the floor and/or seat of your pants? If the vibration is in the steering wheel it is said to be alignment, if it is in the floor or seat then it is in the drive line.

All this information helps the technician to know what to look for. Next the king pins, wheel bearings, tie rod ends, tire mounting, inflation, springs and bushings should be checked. One cannot properly align a truck if any of the suspension components are worn or are bad. Moving the truck changes the measurements. And all these components can contribute to abnormal tire wear and poor handling.

Measuring the truck further confirms the driver’s statements and those of the tire and at this point the technician should be able to adjust and correct the alignment. If the truck wanders or the edges of the tread are worn it is probably the steering axle toe. If it pulls right or left the problem is most likely the aim of the drive axles. Alignment problems are usually a combination of miss-alignment of both steering and drive axle aim or thrust.

There is nothing like driving a properly aligned truck after having become accustomed to driving a misaligned truck. It takes so much less energy when you don’t have to fight the steering wheel or worry about, “where’s that vibration coming from? The tires were just balanced!”

Underinflation is probably the most common problem causing premature and abnormal tire wear that I see. It also reduces fuel mileage. Tires should be inflated to the information on the sidewall before the truck is driven or has set in the sun. How many times have you heard one hundred pounds is enough?  One hundred pounds may be enough if you’re running empty or very light loads. How much money does the truck make running empty?

Who would you say is the expert, the engineer who designed the tire and the tire manufacturer or some technician who doesn’t even know how to properly mount the tire? Following are figures from five different sources. The numbers may vary but the bottom line is the same. Underinflation causes premature tire wear and wastes fuel.

Underinflation - Just how much does 'A few pounds under' cost you?

The following under inflation data results are based on studies performed by the Ministry of Transportation and Communications, Canada, Firestone Tire and Rubber Company and the United States Department of Transportation.
 
These are calculations from the Ministry of Transportation and Communications, Canada.  For every one (1) pound of under inflation in a tire, there is a loss of approximately one-half (1/2) of a percent of fuel efficiency.
 
The following chart is for truck tire tread wear loss based on studies performed by Firestone Tire and Rubber Company.
5% under inflation    =       100% Tread Life
10% under inflation    =       7% Tread Wear LOSS
15% under inflation    =     15% Tread Wear LOSS
20% under inflation    =     25% Tread Wear LOSS
25% under inflation    =     40% Tread Wear LOSS
30% under inflation    =     53% Tread Wear LOSS
40% under inflation    =     65% Tread Wear LOSS
50% under inflation    =     83% Tread Wear LOSS
100% under inflation    =     LOSS OF TIRE


Testing on air filled rubber tires

Lost tire life calculations were obtained from “The Rubber Manufactures Association;” lost fuel mileage calculations were obtained from “American Society for Testing Materials.”

A tire that is properly inflated has less rolling resistance. The result of under inflation is shown by the following data.

UNDER INFLATION AMOUNTS AND RESULTS:
3 psi... Tire runs 9% hotter, looses 5% tread life, and costs 1.9% more fuel
5 psi... Tire runs 16% hotter, looses 22% tread life, and costs 3.1% more fuel
7 psi...Tire runs 22% hotter, looses 28% tread life, and costs 4.4% more fuel
10 psi... Tire runs 31% hotter, looses 37% tread life, and costs 6.25% more fuel

Field tests on trucking fleets have shown under inflation to be as much as 20 - 30%. This means tires are running 20 - 30 psi under inflated. By advancing the above calculations this would lead to tires running 40 - 50% hotter, a loss of tread life of approximately 46 - 50%, and an increase in fuel consumption of approximately 8 - 10%.

Air loss can come from:
A.  No metal valve cap
B.  Punctures
C.  Rim or bead imperfection
D.  Natural porosity of rubber tires and tubes
E.  Flawed tubeless tire liner or tubes.

The most frequent cause of tire failure is under inflation. Under inflated tires increase fuel usage, run hotter, wear faster, and are much more subject to punctures and other road hazard damage.  Hot rubber simply wears faster and has less resistance to cuts and punctures.

Tire miss-mounting is probably the number two most frequent problem I see.  Miss-mounting will cause abnormal tire wear which will cause cupping and vibration.  Abnormal tire wear caused by miss-mounting can easily be mistaken for miss-alignment.  If you look at the tire near the rim you will see a fine ring on the tire.  That ring should be equal distance from the rim all the way around, if not you have a miss-mounted tire.  Lubing only the tire bead, manually installing the tire on the rim, and then standing the tire vertically and inflating will almost always result in a miss-mounted tire.

Proper tire mounting
From talking with the Firestone and Goodyear factory representatives and a Centramatics representative who had attended a Michelin training school I learned the correct way to mount a tire.

A miss-mount may occur when one or more of the following steps are not taken:
  1. CLEAN the rim, particularly in the bead area.  The tire bead must also be clean.  
  2. Both the bead and rim bead area MUST be lubricated before installing the tire.
  3. The tire MUST be inflated with the wheel in horizontal position and with the tire not touching the floor or ground.
  4. The tire should be inflated to 100 or more pounds without the valve core, deflated and reinflated twice before installing the valve core and then inflated to the pounds shown on the sidewall of the tire, usually between 105 and 120 pounds.    

One more very important tip:  Valve cores do not keep air in the tires!  Plastic valve caps do not keep air in the tires either!  You must have a metal cap with a seal inside if you want the air to stay in the tires.
    
Obviously there are too many alignment problems to discuss in such a few words as we have here. I learned to align my own truck with a string and a tape measure by reading three books by Mike Becket of MD Alignment.

West bound I-20 east of Jackson, MS I went 1.9 miles without touching the steering wheel.  First thought that popped into my head was, “Wow, I can do this and get off the road.” It was either get off the road or get divorced.  Then I called MD Alignment and told them. They said the record is 2 miles.  You can link to MD Alignment from www.davenemo.com or find a qualified technician at www.mdalign.com . Reading Mike’s books and learning to align my own truck was not only satisfying but it changed my career.

No, I don’t still use a string and a tape measure to align a truck. Well, on second thought, I do use a tape measure and straight edge to center the drivers and check the steering axle for being square to the frame.

Hope this info has been enlightening.  Drive safely.

Gene Dunlap is an ex O/O with more than seventeen years over the road.

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