As manufacturers of equipment hauling trailers, we at ZIEMAN are vitally interested in highway safety. Experience has shown that trailers and other equipment often become hazardous through either misuse and abuse or lack of proper maintenance. In the interest of customer satisfaction and safety, we present these tips in the hope that they will be passed on to the operator at every opportunity.
***********************************************

Perhaps the single most important consideration is selecting the proper equipment to do the job. The trailer selected should have ample capacity to handle the intended load, plus an allowance for machine accessories, required fluids, and accumulated mud, etc.

The most probable cause of poor trailing is a miss-matched truck and trailer or an improperly positioned load. Too often, trucks are marginal in size for their loads. The truck manufacturers rating for Gross Combination Weight, (GCW), should be consulted if any doubt exists. Note, G.C.W. is the total weight of the truck, plus the trailer, plus the load.

Trucks with long rear overhang, such as long-bodied stake or tilting platform trucks, also tend to be less satisfactory towing vehicles. The long overhang permits trailer side forces to be magnified, and possibly cause weaving. A heavy hitch load on a long overhang can also unload the front truck axle to the point that steering response becomes poor, again resulting in unstability.

An improperly balanced load can easily cause poor trailing. The load should be positioned so that from 10 to 20 percent of the total trailer and load weight is carried by the truck at the pintle hook. Fifth wheel trailers are generally designed to carry a greater percentage on the fifth wheel. Specific models vary, but the ratings are available on the rating tag on the trailer, or from the factory.

A handy solution to the positioning problem is to bolt a stop chock of lumber or angle iron across the front of the trailer bed. The proper position need then only be determined once. After the chock is properly installed, the operator need only park the machine against the chock to be assured of proper load positioning.

If several different types of machines are to be regularly transported on a trailer, a reference line may be painted across the deck. Then a small matching mark is painted on each machine, in line with the deck mark. (This with the machine properly positioned for best towing, as previously discussed.) Then, in daily operation, each machine is simply loaded such that its mark lines up with line across the trailer deck.

Once the load is positioned at the proper location, the next order of business is to keep it there. Good quality tie-down chains are a must. Too often, to save time, tie-downs are improperly used, or even omitted! Loose or unsecured equipment is very hazardous on the highway.

Tie-downs should be applied from structurally strong points on the machine, out diagonally toward the four corners of the trailer deck. This method prevents the load from "walking" in any direction. Although chain binders should not be over tightened, all slack should be removed and a definite pre-load applied to the chains. For long hauls, the tie-downs should be checked and re-tightened after the first 20 miles or so, to remove any accumulated slack.

A general procedure for hooking up is highly recommended. A simple walk around inspection is very effective when regularly practiced. Starting with the coupling hook-up, look for proper coupler closure. Safety chains should be in good condition and attached to a solid portion of the truck frame in such a way that they can't work loose. The hitch area should be looked over for proper bolting and for possible cracked welds. The electrical plug should be firmly inserted into its socket. If applicable, the break-a-way cable should be attached to the truck (not to the pintle eye) securely. Walking on around the trailer, check for tire wear, tire damage, tire inflation pressure, and possible wheel damage. Check that light lenses are intact and clean, ramps and other attachments are properly stowed for travel (if applicable), and the load is securely tied down as discussed above. Again check the wheel area, on passing the opposite side. Having walked all the way around the trailer and arriving at the hitch area again, check to see that the tilt bed locking mechanism is securely engaged in the locked position (if a tilt bed trailer is being used).

Two last items are: turn on the vehicle lights and check for proper functioning of all the lights, and then make a brake check when initially pulling away. This is done by applying the trailer brakes only when first pulling away at two to five M.P.H. It should be obvious that if no braking action is evident, the trip should be discontinued until the problem is corrected.

This simple walk-around procedure can be quickly learned. If it is built into a constant habit by operators, an increased level of safety and equipment reliability is the result.

One important area alluded to in the inspection procedure was tire care. Proper tire care means frequent inspection. Tires should be inflated to recommended pressures. Under-inflation causes poor trailing characteristics in addition to severely shortening tire life. The recommended full load pressure is inscribed on the sidewall of the tire. This is the "cold inflation pressure" and should be checked and brought up to the correct level before the tire is operated. That is: when the tire has had at least one half hour to sit and come to thermal equilibrium. It is normal for truck or trailer tires to heat up during use. This is caused by the flexing that the tire material undergoes. When the air in the tire is thus also heated, its pressure increases, since it cannot simply expand. The point is, that this excess pressure should never be bled off back down to the cold inflation pressure. The loaded operating pressure can be as much as 20 percent over the recommended cold inflation pressure, but this is taken into account by the tire designer when the cold inflation pressure recommendation is calculated.

Low inflation pressure causes excessive flexing, and thus the generation of excessive heat. Excessive heat is the number one enemy of tire life. Too much heat severely weakens the tire material and the bonds between various layers of the internal construction. If the heat level is really excessively high, the tire may immediately blow out, or even catch fire! Proper inflation pressure cannot be over stressed.

Obvious care should not be overlooked either. Imbedded stones and other foreign objects should be removed before they work their way in deeply. Grease and oil should be wiped of. In smog prone or other high ozone areas, the use of silicone based rubber care spray is recommended to prevent excessive cracking that can lead to more serious internal damage.

Bald tires are another danger area. Trailer tires should have ample tread to give good traction on slippery surfaces and to offer good braking adhesion. Also, the danger of blowouts due to striking obstructions is considerably reduced if tires have a deep tread.

Tires should also be reasonably matched. Do not intermix various ply ratings of tires, or radial ply tires with bias ply tires. The resultant miss-match in rolling friction and side stiffness contribute to poor trailing performance and instability.

On dual wheels, tires should be of the same diameter. If they are not, braking force and traction will be uneven. Loads will be distributed unequally on bearings, spindles, and the tires themselves. This condition is easily checked by measuring the rolling circumference of the tires with a steel tape. The circumference of one tire should be within one percent of that of its dual mates. For example, if one tire measures 104 inches in circumference, the other should measure within plus or minus 1-1/16 inch. (1-1/16 inch is one percent of 104 inches, rounded off to the nearest 1 /16 inch).

Wheel care is of no less importance to trailer safety. Correct wheel nut torque will prevent the majority of wheel problems. Loose wheel nuts are by far the most common cause of wheel problems. Bolt hole elongation, hairline cracks in wheels, and broken studs are direct results of improperly tensioned wheel studs. Loose nuts can also cause damage to stud and nut threads, and to ball and seat faces.