Dry Van Trailer Maintenance: Benefits and Best Practices

Many carriers that hire Owner-Operators have a "power-only" operation, where the carrier supplies the trailer and the Owner-Operator just the tractor to pull it. For other carriers, the Owner-Operator is responsible for owning both. At TrueNorth, you have a choice. Owner-Operators must own their tractors, and whether you want to own or lease a trailer (at cost) through us for $250/week is 100% up to you.

Benefits of Leasing or Owning Your Trailer

Leasing or owning your trailer comes with two distinct advantages:

  1. Increased confidence in the equipment. Drivers often complain about pulling substandard - or poorly maintained - trailers that make life miserable on the road. While not owning the trailer relieves you of trailer maintenance tasks, having control of your equipment can bring extra comfort and security to your hauls.
  2. Increased control over your loads, schedules, and of course, profits. When you have the trailer at your disposal, you get to enjoy the freedom that comes with it.

With proper maintenance practices, you, too, can take advantage of this freedom for longer!

Best Practices to Maintaining Your Trailer

The following maintenance best practices will help to ensure that your trailer is in top condition and therefore enable you to maximize your profits -

Air Brake System

One of the first benefits is balanced air brake system operation. While anti-lock brake system (ABS) and various stability control systems take over in many potentially dangerous circumstances as the vehicle reaches the limits of adhesion to the road surface, the basic response of the air brake system is controlled by various simple mechanical components. The rig's air brake system must react quickly and evenly when you apply pressure from the treadle valve under the brake pedal. In doing so, the system stores air for brake application in tanks at each axle. Then, when you apply pressure with the treadle valve, all that has to be sent the length of the rig is an air signal. The signal then opens devices called relay valves that amplify that signal and control flow into the brake chambers‚ the air pressure cylinders that actually rotate the slack adjusters and apply the brakes via a camshaft. The pressure applied to the chambers is proportional to the signal and the pedal position.

You're probably familiar with runaway trucks on long downhill mountain grades and the escape ramps that can stop the rig without damaging it. A tractor-trailer rig can run away on a long downgrade for many reasons, and one of the most common reasons is a lack of balance in the air brake system. A properly maintained system in proper adjustment will apply all ten wheels of a 5-axle tractor-trailer evenly. A system in that kind of working order has a very high capacity for heat and normally won’t overheat or allow a runaway. But if only two or three, or even four, of the five axles, are working most of the time, the result can be horrifying. Brake drums that are too hot expand, killing the pressure the chambers can apply to the linings while also causing the linings to fail to contact the drum properly. Poor contact occurs because of expansion-related distortion. Braking power can drop to the point where the rig has very little stopping power.

Ensure All Relay Valves Open Together at the Same Crack Pressure

Take your rig to a shop where brake work is done and have them make sure all the relay valves begin to open at just about the same crack pressure, the point where treadle pressure starts causing the relay valves to send air to the chambers. Slightly different valves may be installed in different positions to ensure proper timing, but the basic idea is that all the valves open together. Have the shop ensure all the valves have the same specifications and will ensure simultaneous and balanced application pressure to all the axles.

Ensure Snubbing

You can help ensure proper operation by "snubbing" which means NOT applying just enough pressure to maintain a steady downhill speed, but instead repeatedly applying at least 10-30lb of pressure and slowing the rig, then releasing the pedal to restore speed. This may also slightly help to cool the linings and drums as air is allowed to flow between the linings and drum. Snubbing is recommended in the CDL manual.

Use the Correct Settings for Descending Long Grades

Using an engine brake at the maximum power setting with the engine at a high RPM and descending a long grade at a low speed in a low gear is also essential on the longest grades.

Check and Maintain Brake on Trailer Axles and Other Parts

Of course, brake maintenance on the trailer axles and the whole rest of the rig is essential. Grease your automatic slack adjusters at recommended intervals with the grease recommended by the manufacturer, not just a multi-purpose chassis grease. Check the brake stroke frequently to make sure it stays within limits. And, whenever doing a brake job, replace all the return springs, rollers, and other parts, usually contained in a quality brake overhaul kit. Use quality remanufactured or new brake shoes and lining that meets original factory specs. Always make sure the camshaft bushings are not worn by checking end-play and the clearance between the shaft and bushings (side-play) so there will be only minimal clearance between them and the camshaft, or better yet replace the bushings when replacing linings. Don't machine drums more than allowed, as the mass of the drum helps take heat away from the linings.

Drain Air Tanks Weekly

A significant adjunct to this mechanical maintenance is weekly draining of all air tanks, and proper maintenance of a good air dryer, where the desiccant that removes moisture and the filters need to be replaced at stated intervals.

Other Recommendations for ABS Maintenance

ABS maintenance is a complex matter, but here are a few general points: 

  • Wiring needs to be kept in good condition and repaired when insulation gets frayed. 
  • Troubleshooting is often available via the proper factory manuals and using the ABS electronic modules themselves to signal and reveal stored trouble codes
  • Common problems include sensors that are not adjusted to maintain the proper distance from the tone rings mounted on each wheel, damaged tone rings, or defective sensors.
  • Any wiring that needs repair should see replacement with sealed wiring harnesses. Fill plug type connectors with di-electric grease or use full soldered connections. 
  • Don't check for voltage by using a pinprick probe, as even a tiny hole in insulation will allow that wintry mix of chemicals to wick in and corrode wiring and connections.

Trailer Wheel Maintenance

Check Wheel Lug Nut Torque Weekly

Check wheel lug nut torque and make sure it's up to snuff as often as weekly. When removing and then replacing a wheel for any reason, it's critical to put a drop of 30 weight oil on each stud that each lug nut screws onto. Then torque the lug nuts in a cross-the-wheel pattern in three stages to specification. Finally, and this is very important, drive the truck 50-500 miles and retorque after the wheel has seated.

Check and Adjust Wheel Bearing Lubrication and Settings

Wheel bearing maintenance is also critical. A wheel off due to lack of lubrication or improper setting of bearing end-play is a deadly business. Check the fluid level frequently and refill as necessary if using oiled bearings with wheel seals. Disassemble and replace bad seals, then refill with oil to the proper level. Greased bearings need to be removed and properly repacked at stated intervals. Adjusting the wheel bearing properly is essential after thorough repacking that pushes grease thoroughly into the bearing (a special jig is available for doing this).  And it must be done with a torque wrench, making final adjustment precisely per factory specifications, which often involve spinning the wheel as you torque, and then backing off the nut that determines bearing free-play a specified amount before inserting a cotter pin (to create a very slight end-play). Pre-adjusted wheel bearing systems that are torqued to specification where spacers determine the proper end-play are also available. Proper adjustment is critical both for safety and good fuel economy.

The entire trailer should be greased as often as possible using the proper, multi-purpose grease. This includes the 5th wheel and trailer kingpin as proper greasing will not only extend the life of its locking components but make for easier turns and less tire wear.

All-Wheel Alignment for Both Tractor and Trailer

Speaking of fuel economy, one big help in this area, as well as to extend tire life, is all-wheel alignment. You should periodically be taking your entire rig to have every axle aligned‚ both the tractor and the trailer. Any so-called "dog-tracking" where the trailer doesn't follow straight behind the tractor will have a negative effect on both fuel economy and tire life.

A good starting point after basic brake and wheel maintenance is to read and study all the applicable manuals, including those from the trailer manufacturer and component manufacturers, and the CDL manual. Walk around the trailer and study all the safety decals, too.

The Importance of Regular Upkeep

Cleaning

In a winter environment where salt, calcium chloride, and magnesium chloride are all used to melt ice, keeping a trailer clean is especially important. Experts say these combine to make a paste that sticks on metal and will actually absorb moisture. It's ideal to clean your trailer at least weekly in winter. If possible, use a brush on the metal to properly remove this stuff, or a pressure washer at a low pressure setting that won’t force water into nooks and crannies where it won't drain. Use fresh water to do this as often as you can, as a truck wash may not be ideal since they need to recycle water.

Inspections

Another area of concern, since trailers work hard just supporting the load in a high-vibration environment, is weekly inspection of the trailer's structure. Look at weld areas that support weight, suspension parts, and all the parts that keep the load contained like side rails and tie-down mounting points. Look at the body structure crossmembers, cross-bracing, decking, and the main beams on a flatbed. Less massive structural members on van trailers are similarly critical, especially when it comes to cracking. Also look at suspension hangers, spring shackles, and the bushings that keep air suspension systems properly aligned. Look at air springs and brake lines to see if there are any signs of chafing or cracking. Refer to our blog post CVSA Inspections: Understanding and Preparing for Them or purchase these in a booklet at www.cvsa.org for less than $25 to become familiar with the criteria that inspectors use at roadside.

Repainting and Refinishing

Finally, while effective washing and cleaning will extend not only the life of the trailer's metal structure but even the life of the paint or other finish, repainting or refinishing it every few years will not only preserve the structure, it will help ensure good resale value. Aluminum trailers may benefit from a polyurethane clear coat. Steel trailers should be sandblasted before repainting to ensure a durable finish. Repainting is typically done every 3-5 years to keep a trailer looking like new.

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