Yes, Pre-Trip Inspections are Legislated because the evidence if you lie will give you up!

When you get called about your fleet accident, nine times out ten you are hundreds of miles/kilometers  away and now you have to think, what caused it, did the driver do his or hers pre-check inspections and what items WILL THE POLICE find in their investigation.  It is not always the truck drivers fault, but if you do not enforce the rules and guidelines set for commercial vehicle YOU TOO as a supervisor now became liable because the following things WILL COME OUT in the site investigation.

 Truck brakes are often blamed for causing crashes. Most commonly, this claim comes from the truck driver, who is trying to transfer blame from himself to a failure of the truck. When this claim is made, interested parties often assume that a catastrophic failure caused a complete loss of braking force. Stated differently, the assumption is that a defective component of the brake system spontaneously failed causing the brakes to no longer function. In reality, brake systems are designed so that a complete catastrophic failure is an extremely rare event. Therefore, alleged brake failures usually are not failures at all but performance problems stemming from deficient maintenance.

Truck braking systems can usually still provide low levels of braking force even with maintenance deficiencies. This low-level braking force will allow the truck driver to adequately stop the truck for normal operations such as slowing for a stop sign. However, when a high level of braking force is demanded in an emergency, these deficiencies will show themselves. Even though the driver is applying the brakes very hard, he will not get the expected result, which is a high level of deceleration. In this case, the brakes are slowing the truck, but not as quickly as the driver expects them to. Most likely the driver will perceive that the brakes are not working at all. In reality, the brakes are working, but not at the level of performance expected for an emergency application.

Brake Imbalance
Another brake performance problem that results from poor maintenance is brake imbalance, which can be caused by deficiencies that affect some of the brakes in the system but not others. Brake imbalance can also happen by having mismatched brake system components that cause some brakes to work harder than others. Brake imbalances can lead to instability during braking, brake fade, and brake fires.

Good brake balance is a result of having properly matched, maintained, and adjusted brake system components, as well as a properly loaded trailer. There are two main types of brake balance; torque balance and pneumatic balance. Proper torque balance is created by having matched mechanical components, which are working properly and adjusted correctly. If a truck has a torque imbalance, some of the brakes will work harder and lock up easier than others. When a truck has a torque imbalance problem, brakes are usually affected individually. Proper pneumatic balance is created by having equal air pressure at all wheel ends. When a truck has a pneumatic imbalance, some of the brakes will also work harder and lock up easier than others. However, pneumatic imbalance will be manifested at one axle or one set of tandem axles, such as the tractor drive axles or the trailer axles.

Brake imbalance is one of the more common causes of loss-of-control crashes for air-braked trucks. If a truck does not have good brake balance, it will have a propensity toward either jackknifing or trailer swingout. Jackknifing occurs when the tractor's drive axles achieve a higher level of braking force than the trailer axles. When this happens in an emergency or low traction situation, the tractor drive axles will likely lock up while the trailer axles are still rolling. With the tractor's drive axles locked, they will lose directional stability and the unbraked trailer load will push the tractor into a rotation around the king pin. Trailer swingout is similar to a jackknife, but occurs when the trailer axles achieve a higher level of braking force than the tractor. With the trailer brakes locked and directional stability lost, the tractor will drag the trailer, which will then begin to swing out.

As you can see, if the brake system is not balanced for any one of a number of reasons, the result will be that some of the brakes will have to work harder than others. This imbalance can cause the hardest working brakes to become too hot, resulting in brake fade or fire. This usually happens when the truck with a brake imbalance is descending a long steep grade. As a truck is being braked, the properly working brakes will be doing more than their share of the work. This will cause the overworked brakes to become much hotter than they should be and may eventually lead to brake fade. When the good brakes fade, the only brakes available to stop the truck will be the deficient ones. Additionally, as the brakes get hotter, they can catch on fire and/or catch the corresponding tires on fire. A brake imbalance will also affect the stopping distance. Because the deficient brakes will not be working at their peak efficiency during hard brake applications, the truck will take longer to stop.

Brake Inspection
A brake imbalance can be discovered by inspecting the brake linings. If an imbalance exists, the linings at some of the wheel ends will wear faster than others. By law, a truck driver is required to check his vehicle on a daily basis and note any problems, such as improper brake balance, on his daily log.

Since improper brake balance could have either caused or contributed to cause a crash, it is always a good idea to have the brakes tested after a truck collision. This kind of inspection requires specialized equipment that can supply and regulate air pressure to a vehicle that may have a damaged air-supply system. Information gathered during this inspection can be used to calculate brake force in order to determine the efficiency of each brake. Then, this information can be used in the reconstruction of the crash to determine not only what the pre-braking speed of the truck was but also if the brake condition was a causative factor in the crash.

Some times and based upon your DAILY LOG BOOKS Truck crashes are commonly caused by mechanical failures. Most of these failures are not spontaneous, but progressive, and stem from maintenance deficiencies. Some examples of maintenance deficiencies that cause truck crashes are braking defects caused by oil-contaminated brakes, braking defects caused by brakes that are out of adjustment, tire failures from tires that are run under-inflated or over-loaded, wheel separations caused by wheels and hub assemblies that are improperly installed or maintained, and steering system components that are used and worn to the point where they separate and fail. The standard of care for maintaining and repairing trucks makes the motor carrier and its drivers responsible for keeping their trucks in a safe condition at all times. Since progressive failures can be identified, allegations of mechanical failure are really an admission of motor carrier and/or driver failure rather than an excuse for a truck crash. The minimum standard of care for truck maintenance is established by the Federal Motor Carrier Safety  in North America.

The more important and widely overlooked maintenance standard comes from the standards is a performance standard that requires a motor carrier to have a maintenance system by stating "Every motor carrier shall systematically inspect, repair, and maintain all motor vehicles subject to its control." The goal for this required maintenance system is that all parts and accessories shall be in safe and proper operating conditions at all times. Since different trucking operations place varying mechanical demands on equipment, the PMI interval required to meet the goal of keeping a truck safe at all times is operationally specific. For example, a trucking company hauling heavy construction equipment that commonly operates trucks in off-road construction sites will likely require more frequent PMIs than a motor carrier using trucks in long-haul highway operations.

A good maintenance system will not only uncover deficiencies in the vehicle, but also deficiencies in the maintenance system itself. For example, if DVIs are being done properly, then a PMI should only find defects that could not be found by a investigation. So, if a truck PMI finds defects that should have been identified by a DVI, the maintenance system should specify remedial action for the driver who either does not understand how to properly inspect his truck or does not inspect it at all. As another example, if PMIs are finding a large number of defects, then PMIs need to be done more frequently. When a truck has a breakdown or is cited for a violation during a law enforcement inspection, the maintenance system should specify a procedure for determining how the truck got into its defective condition so remedial steps can be taken to prevent it and other trucks from being in that condition again.

Crashes caused by wheels coming off of vehicles are commonly referred to as wheel runoff crashes. Two primary failures cause wheel runoff crashes. One is a failure of the wheel mounting system, such as the wheel studs, lug nuts, etc. The other cause is a failure of the hub and wheel bearing assembly. Most commonly, these failures are related to improper or deferred maintenance, but some are also linked to manufacturer's defects.

Wheel system failures are primarily caused by the improper installation of a wheel that causes it to be loose or become loose. Commonly, a loose wheel causes the wheels studs to break and the wheel and tire to separate from the vehicle. Many root causes lead to loose wheels, but most of them are associated with over-torquing or under-torquing the lug nuts.

A bolted joint, such as a wheel mounting system, works by tightly clamping two surfaces together. The friction of the two mated surfaces and the force created from clamping them together with bolts (Clamp Load) allows the surfaces to resist movement. The amount of friction and Clamp Load determines the level of resistance the joint has to movement.

Clamp Load is created by tightening the bolts against the mated surfaces and is normally measured in foot pounds of torque with a torque wrench. If the bolt torque specified for a joint is applied, then the resultant Clamp Load should also be within specification. However, variations in the system such as rust or lubrication on the threads can affect the Clamp Load vs. torque relationship. Items in place between the mated surfaces can reduce the joint's friction and also alter the relationship between bolt torque and Clamp Load. This is called a Soft Joint.

Two concepts are important to understanding how a bolt works. They are Elastic Deformation and Yield Point. Elastic Deformation is metal's or, in this case, a bolt's ability to stretch and spring back to its original shape. Yield Point is where the bolt has been stretched past its elastic limit and can no longer spring back to its original shape. This stretching of a bolt and its pulling back creates Clamp Load. If, however, a bolt is over-torqued, and stretches past its Yield Point it can no longer maintain the Clamp Load.

Over-torquing is likely the most common wheel system failure due to the widespread use of impact wrenches to install wheels. Using an impact wrench to install wheels commonly causes the wheels to have 3 to 5 times the specified lug nut torque. The use of lubricants and anti-sizing compounds on the threads of the wheels studs or lug nuts can cause an even higher degree of over-torquing.

The specific torque required to install a wheel varies from vehicle to vehicle. Generally, the proper torque for the lug nuts on passenger vehicles will be around 100 foot-pounds and the proper torque for big trucks will be around 400 foot-pounds. Impact wrenches commonly used to install wheels on passenger vehicles are capable of producing 300 to 500 foot-pounds of torque. Impact wrenches used to install wheels on big trucks can produce 1200 to 2000 foot-pounds or torque.

Under-torquing is just simply not tightening the wheel lug nuts enough, causing the wheel to be loose. Under-torquing can be caused by corroded and damaged wheel system components. It can also be caused by using a cheap or worn-out impact wrench or by having a low air-pressure supply to an impact wrench.

Another common cause of wheel system failures is too much wheel paint thickness. As specified by the Recommended Practice PR222B from The Maintenance Council (TMC) of The American Trucking Association "Total thickness of the dried paint coating on each side of the wheel mounting face must not exceed 3 mils(.003 inch)." If the wheel's paint is too thick, then a soft joint is created and the system can fail.

Paint thickness defects are not only caused by original production painting but also more commonly caused by the recondition or "remanufacturing" of wheels. Wheel reconditioning generally involves "sandblasting" used truck wheels and repainting them to make them look new. The reconditioning of wheels is typically being done by tire dealers and tire retreaders who do little to control paint thickness.

There are four primary causes of hub failures. They are lack of lubrication, overloading the vehicle, installing the axle nut too tight, or installing the axle nut too loose. Usually, hub failures are progressive and will produce some evidence of the impending failure. Evidence of a failing hub can include leaking hub seals, tire tread wear anomalies, sounds, smells, smoke, and steering wheel feedback.

The bearing preload is adjusted by tightening the axle nut down against two cone-shaped bearings. As the nut is tightened, the hub assembly becomes tight and the play is removed from the system. Once the bearing preload is adjusted, a lock is installed to prevent the axle nut from moving. Although, there are many types of locks for axle nuts, some common ones are a cotter pin placed through a castled hex nut or a keyed washer placed over a flat hex nut followed by a second nut to hold the washer in place.

The proper method for adjusting and preloading bearings has 5 to 8 steps, but is rarely followed. Here is an example of one methedology published by the bearing manufacturer Timken:

1. Torque the adjusting nut to 200 lb-ft to seat the bearing components. Always rotate or oscillate the wheel while torquing the adjusting nut to ensure that the rollers are fully seated against the cone large rib.
2. Back off the adjusting nut one full turn or until it's loose.
3. This is where you actually establish end play. Torque the adjusting nut to 50 lb-ft while rotating the wheel hub assembly.
4. Back off the inner (adjusting) nut the appropriate amount as indicated by the chart at right; e.g., 1/6 of a turn for a 12-threads-per-inch front steer axle. See chart at right for the exact back-off amount.
5. On a single-nut system, install a cotter pin. On a double-nut system install a jam nut and torque it to the proper specification, which varies depending on the size of the nut.

Once these steps are preformed, also recommended is that the hub's end-play be measured with a dial indicator to verify proper preload.

A hub that is adjusted too loose will allow the hub and wheel assembly to oscillate laterally. This will cause bearing wear and will cause a further increase in hub looseness. The loose hub allows excessive movement of the bearing rollers resulting in roller cage wear and uneven race wear or "scalloping". If not repaired, the bearing play will increase progressively to the point where the hub fails.

A hub that is adjusted too tight will not have a lubricant barrier between the bearing rollers and bearing races. Without a lubricant barrier, the bearing will overheat and fatigue. This condition will lead to full bearing lock up and hub separation if not corrected. This condition will be evidenced by heat discoloration and fatigue spalling on the bearings.

Overloading a hub creates similar conditions as over-tightening the hub. The excessive weight forces the lubricant from between the bearing rollers and bearing races on the loaded side of the bearing causing localized heat and fatigue.

Lack of lubrication also causes metal to metal contact between the bearings and races. This results in excessive heat, bearing and race scoring, and microspalling fatigue. This condition, if not corrected, will lead to bearing lock up and hub separation.

The mechanism of failed hub separation can vary by the design of the hub. Some hubs have a small outer bearing and axle nut. When the outer bearing fails, the hub can just slip past the axle nut and remaining parts of the outer bearing. In hubs with large outer bearings, separation of the hub occurs when the oscillating hub causes the axle nut to be pulled off the axle like a bottle cap. In other cases, the axle nut is pulled off the axle, ripping the threads out of the axle nut and leaving the threads on the hardened axle relatively undamaged.

Tread detachments are the most common tire failures that cause loss-of-control crash. Tread detachment may or may not result in rapid deflation of a tire. Since tread detachment throws the failed tire out of balance and applies a lateral force to the vehicle, rapid deflation of the tire is not required to cause a loss of control of the vehicle. Possible causes of tread detachments include fatigue failures such as under-inflation/overloading, excessive speed, unrepaired injuries, repair defects, impacts, mounting damage, tire age, and internal rusting.

Fatigue failures are most typically caused by the over-deflection of the tire as a result of under-inflation and/or overloading. Over-deflection will produce evidence on the tire such as darkening of the inside wall of the tire, wrinkling of the inside wall of the tire, and heavy abrasions on both the inside and the outside wall of the tire.

Fatigue failures can also result from other conditions such as severe steering or axle misalignment. Alignment conditions can cause a tire to scuff under normal operation. Constant and severe scuffing of a tire will generate heat and will fatigue the tire. If scuffing caused by misalignment exists, it will be evidenced by irregular wear patterns on the tire tread.

Impacts to the tread surface of the tire can weaken or break the tire's structure. Impacts are characterized as a "severe, concentrated impact with a foreign object, curb or pothole". Sources also report that "total tire failure could be immediate or delayed depending upon the severity of the impact." Impacts to the tread area of the tire create a break across the tire crown with corresponding perpendicular breaks in the tire sidewall.

Tire aging is a commonly cited cause of tread separations. Tires, like any other rubber product, have a limited service life. Mercedes-Benz says "Tires undergo an aging process even when they are not in use... The rubber parts become less elastic, the steel webbing inside the tire corrodes and the rubber mixture of which the tread is formed hardens." Long existing standards warn of the hazards of using old tires and indicate that a tire that is six years old or more needs to be inspected. More recent standards require that tires six years old or more not be installed on a vehicle and that tires ten years old should be taken out of service.

Internal rusting is a well-known cause of tire failure. Rusting of the steel cables in the tire occurs as a result of injuries and age cracks that expose the steel to contaminants such as water and road deicers. For this reason, tire repair standards require that a repair not only seal an injury to prevent inflation air from escaping the tire but also seal the injury to prevent contaminants from entering the tire casing. Rusting of a tire's steel cables weakens the steel and weakens the bonding of the steel to the rubber. A tire weakened from rust will ultimately fail by tread separation.

Retread failures are misunderstood. The common perception is that retreads have adhesion-related problems that result in the loss of tread from the tire casing. In reality, this type of adhesion failure is very uncommon. Adhesion failures in a retread tire are generally localized and result in the tire tread coming off in small pieces. When these pieces of the pre-cure retread separate from the tire, no steel will be contained in the separated rubber.

The tire retread industry accepts the use of retreads on steer axles if specific guidelines are met and a tire is certified for use on a steer axle by the retreader. According to a retread industry association, TIA (Tire Industry Association), the retread identification code should contain an F1 after the date code to indicate that a retread tire has been certified for use on a steer axle. The standards for certification of a retreaded tire for use on a steer axle are conditional and exclude the use of tires with certain identifiable casing defects. Additionally, these standards only promote the use of retreads in short-haul, low-speed, high-wear/short-tread-life operations.

Service failures that occur during the mounting, inflating, and handling of tires and wheels commonly cause catastrophic and fatal injuries to tire mechanics. Inflated tires contain a large amount of potential energy and a rapid release of that energy can injure anyone in the trajectory of the escaping air and objects propelled by the escaping air. All tires pose some risk, but the larger higher-pressured tires are more dangerous than smaller lower-pressured tires. This regulation has specific guidelines for handling tires and also requires that anyone handling large tires receive tire service training.