Trailer Mechanical Maintenance

The living quarters of travel trailers required basically the same kind of routine maintenance as any other RV:  regular cleaning, checking for and sealing leaks, servicing appliances, dumping and flushing holding tanks, winterizing (if you don't live in the Sun Belt), and sanitizing the fresh water system.

Unlike motorized RVs, travel trailers have only a few mechanical components you'll need to take care of.  Motorized RVs have literally ALL the mechanical systems (and potential problems) as any other motor vehicle:  engine, cooling system, transmission, drive line, suspension, tires, and brakes.  Travel trailers don't have engines or power trains so they require a lot less mechanical maintenance but there are things you need to watch for and tasks you need to do on a regular basis.

Tires and wheels.  One of the most visible and most obvious mechanical parts of a travel trailer are the tires and wheels.  While some ordinary car or truck tires may fit your trailer wheels, you should use trailer rated tires.  They are designed specifically for the kind of use (or non use) they get on trailers, including long periods in storage.  Check your tire pressure frequently and always maintain the proper pressure.  Your trailer should have a tire pressure label or you can get it from the owner's manual or the manufacturer.  Lacking any specific recommendations, inflate the tires to the maximum pressure indicated on the side wall.  If your trailer is light, using the maximum side wall pressure may over inflate the tires.  When that happens you will see excess wear in the center of the tread and the trailer may feel "squirrelly" in the wind or when buffeted by passing trucks.   Over inflated tires also create a harsher ride that might you might notice as vibrations or bumping transmitted through the hitch to your tow vehicle.   If your tires are under inflated you will see excess wear on both edges of the tread and the tires may run hot, which reduces their life expectancy and, if the get hot enough, can cause blowouts.  Excess wear on only on one edge means the axle is out of alignment, caused the tries to be dragged a little sideways.  Mushy tires will increase rolling resistance, making your tow vehicle work harder to pull the trailer and lowering fuel economy.  One way to ensure proper inflation is to have your trailer weighed and inflate the tires using a weight/inflation chart.

In addition to proper inflation, regularly inspect your tires for wear and side wall cracking.  Most RVs, including travel trailers, get limited use and tread life usually exceeds the expected life time of the tire.  Side wall cracking is an indication that the tires have "timed out" and are becoming susceptible to blowouts.  Wear patterns can be an indication of other problems so monitor them closely.  As mentioned above, excessive wear in the center of the tread indicates over inflation; excessive wear on both edges indicates under inflation; wear on only one edge is probably due to misalignment;  more wear on one tire than the others on a trailer may indicate a brake is dragging on that wheel or that the wheel bearings are going bad and have extra resistance.  Brake or wheel bearing problems will also result in the affected tire(s) getting hotter than the others.

Lug nuts are one of the most often neglected components of trailers.  Sometimes they are hidden under hub caps but even when they are exposed, most people tend to ignore them.  If they are in good condition and have been properly torqued they usually won't have any problems.  However, the constant vibration can loosen lug nuts.  One indication is a shiny ring behind the nut(s) where the wheel has been wobbling.  It is a good idea to check your lug nuts regularly, at least before each trip.  You might do it using a proper lug wrench and making sure they feel tight but the best way is to check them with a torque wrench to be sure they are correct.  When you tighten lug nuts or other fasteners the bolt inside is slightly stretched as the they are tightened.  A torque wrench measures just how tight the fasteners are.  Torque specs are provided by manufacturers indicating the proper tension needed for them to operate at design capacity.  Under torqued fasteners may come loose; over torqued fasteners may stress the bolts and nuts and cause them to fail prematurely.   Extreme over torquing can even strip the bolts and nuts.  When checking the lug nuts also inspect the wheel for signs of damage:  dents in the rim or any cracking.  Have someone stand behind the trailer and watch as you pull it forward a few feet to see if the wheels wobble.   Wobbling wheels may be bent, loose, or may have bad wheel bearings.

Hubs and wheel bearings are another part of the system that is "out of sight, out of mind" for many people.  That can be a dangerous mistake!  Properly lubricated wheel bearings will last for many years and many thousands of miles if not abused.  Abuse comes when the the axle is overloaded or the lubricant is compromised by water, dirt, or solvents or simply get used up.   Check your owners manual or with your dealer to determine the recommended schedule for servicing your wheel bearings.  Lacking any other guidelines, service them at least once a year, more often if they get submerged (e.g., a boat trailer, fording streams, or caught in a flood).  Servicing them consists of removing the bearing from the hub, cleaning an inspecting the bearings and the hubs for wear, re-packing the wheel bearings with appropriate grease, reinstalling the wheel bearings and torquing the axle nut to the proper specification.  Most axle nuts have a slotted cover that has a cotter pin that goes through the slots and through a hole in the end of the axle to keep the nut underneath from spinning as the wheel turns.  Always use a new cotter pin.  The old one  will have been weakened by bending and unbending as it is installed and removed and could break.  If the axle nut is too loose, the wheel will wobble, stressing the hub, bearing, wheel and tire.  If the axle nut is too tight,  it will put extra pressure on the wheel bearings, causing them to overheat and wear faster.  When you remove and inspect the bearings some of the things to look out for are contaminates in the grease (dirt, water, metal shavings), burned grease (may be black and dusty instead of greasy or may only smell burned), any loose or missing balls in the bearing, any signs of wear on the bearing race inside the hub.  Damaged races can sometimes be pressed out and replaced but very often by the time the race is damaged the hub also needs to be replaced.   Packing the wheel bearings with grease before reinstalling them is a crucial step.  You want to make sure the grease fills the bearing.  There are tools that clamp around bearings and have a grease fitting that allow you to use a grease gun to pack the bearings but the most common way of packing bearings is to place a dollop of grease in one hand  (your left hand if you're right handed or your right hand if you're left  handed), then hold the bearing firmly by one edge in your dominate hand with the wide side of the bearing down.  Press  the edge of the  bearing opposite your hand down into the grease in the other hand until new grease squeezes out the top side of the bearing.  Then rotate the bearing slightly to the next position and repeat until you have packed grease all the way around the bearing.   Different applications may require different types of grease.  Ordinary wheel bearing grease is the most common, but boat trailers should use a special waterproof grease.  General purpose grease is usually OK for most trailer wheel bearings but for best results use Disc/Drum Brake Wheel Bearing Grease.

Some trailer axles have a grease fitting in the end of the axle so you can lubricate the bearings without having to remove and repack them.  Even with these you will want to remove the hubs and inspect and repack the bearings every year or two.  With other types of axles, even if they have an added on bearing protection system like a Bearing Buddy that lets you use a grease gun to push grease into the outer bearing, the hubs should be removed and the bearings inspected and repacked at least once a  year.  The after market bearing protection systems do not adequately lubricate the inner bearings.

Trailer suspension.  Most travel trailers I've seen have leaf springs that connect the axles to the frame and absorb some if not most of the bounce when the wheels encounter an obstacle or rough surface.   A few also  have shock absorbers.  Sometimes shock absorbers can be added to minimize bouncing of the trailer.  Since you're not riding in it, minimizing bouncing mainly helps avoid unwanted rearranging of the contents and reducing stress on coach components but if you can feel excessive bouncing of the trailer through the hitch into the tow vehicle, you might want to explore the possibility of adding shock absorbers.  Springs generally don't require a lot of maintenance.  For the most part you just need to make sure all the fasteners are tight and not damaged.   Spring shackles should be greased periodically.   Lacking any specific recommendations from the manufacturer, they should be lubricated at least once year.  When you inspect your springs, the leaves should all be neatly stacked on top of each other, not twisted or skewed and there should be no signs of cracked or broken leaves. Usually the springs are slung  under the axles and held on by massive U-bolts.   Sometimes, if the ride height is too low, you can do what they call "flipping the axle".  That generally means moving the springs so they rest on top of the axle instead of being slung underneath it and raising the height of the body several inches.  If you have a drop axle and need even more height, it might be possible to literally flip the axle over.  Normally drop axles drop down between the wheels to  lower the trailer body. Flipping it over or replacing it with a straight axle will then raise the trailer body.  Exercise caution and check with a qualified technician before "flipping" an axle.  Doing so may have unexpected consequences.  For example, some axles are designed so the wheels tilt slightly.  Flipping them over will reverse the angle of the wheels, which will affect handling and tire wear as well as clearance inside the wheel wells.

More on trailer springs.  Most trailers have leaf springs that require little maintenance but over time, the vibration and flexing may cause one or more leaves to break.  If you have to replace the springs, be sure to measure them so you get the right length and get the right style shackles.  Always replace springs in pairs.  Doing just one side will likely result the new side being higher than the old one and will stress both the axle and the body of the trailer.  Sometimes you can increase ride height and weight capacity by using heavier springs.  Sometimes you can also adjust ride height by changing the spring shackles.  But be aware that using longer shackles may put extra stress on the shackles and their mounting points because of additional leverage so consult a suspension expert first.  In addition to replacing springs,  a good spring shop can re-arc and rebuild existing springs.  Re-arcing restores the shape and function of the original springs.  Rebuilding replaces damage leaves and/or adds leaves for extra capacity. 

Trailer axles.   Trailer axles are usually pretty sturdy and don't require any maintenance.  They may be solid or tubular, round or square, straight or drop style.  You should visually inspect your axle(s) from time to time to ensure they are securely attached, properly aligned, and have not been damaged.  Bent axles will affect handling and cause excessive tire wear.  Cracked axles are rare but are in danger of breaking and dropping your whole trailer onto the pavement!  If you have a bent or damaged axle you might be inclined to try to repair it rather than replace it.  Not a good idea!  Damaged axles should be replaced.   You will want to find a matching axles (length, diameter of the tubing, straight or drop style) unless you have a need to change the ride height. 

Trailer hitch.  One more critical mechanical component is the trailer hitch.  Hitches take a lot of stress and, over time, may develop problems, such as cracking in various places or stretching where they fit around the ball (bumper pull trailers).  The pin on 5th wheel hitches may get worn or bent or become loose.  Worn or damaged components should be replaced as soon as possible as a failure is likely to have catastrophic consequences for the trailer, the tow vehicle, and any other nearby objects or person.  The hitches on some trailers are welded to the tongue; some are bolted on.  If you're is bolted on, you can probably replace it yourself.  For best results use new bolts and nuts when  you replace the hitch.  If the hitch is welded on, it will have to be cut or ground off and a new one welded on.   Many trailer owners overlook the need to grease the ball when hooking up their trailers.  Often the ball on the receiver on the two vehicle is a nice, shiny chrome and greasing it makes it look ugly and you get dirty grease all over your pants whenever you happen to brush up against it.  However, greasing the ball will reduce wear so the ball and hitch last longer and it minimizes binding between the ball and the hitch when turning.  Sometimes an ungreased hitch will create an annoying squeak when pulling the trailer.  That squeak is a sign of excessive wear happening every time the ball moves inside the hitch.

About the only other mechanical parts on travel trailers are tongue jacks and stabilizing jacks.  Tongue jacks may be manually or electrically operated and usually need little maintenance other than cleaning and lubrication.  Be sure to periodically check the electrical connections on electric jacks.  A common problem is a loose or corroded ground wire.  Manual jacks usually are operated by  a crank and the handle on the crank may need cleaning and lubricating.  The gears inside the jack should be packed in grease.  Sometimes you can service these gears, sometimes you can't.  If the jack gets difficult to turn when there is no weight on it, try cleaning and lubricating the gears if you can get to them.   If you can't service them, about your only option is to replace the jack.  Not all trailers have stabilizing jacks but if yours doesn't, you may want to add them.  The most common stabilizer jacks I've seen on travel trailers are scissor jacks.  They are welded or bolted to frame.  You may only have two at the back (and use the tongue jack to level the front) or you may have them at all 4 corners.  They usually require little maintenance, other than cleaning and light lubrication on the moving parts (the screw itself and the hinge points for the scissors).  Some light weight tent trailers have simple stabilizers that drop down and lock into place.  They don't provide any lift for leveling, but will keep the trailer from tilting or bouncing.  If any tongue or stabilize jacks are bent they should be replaced.  Sometimes you can straighten bent parts to get by for a while, but having been bent and straightened they will have been weakened and are likely to bend again -- and again -- until they cannot be corrected or fail completely, usually causing additional and expensive damage to the trailer.

Trailers also need maintenance similar to your house.   The plumbing, heating and air conditioning, and electrical systems will experience the same kinds of wear and tear and need the same kind of preventative and restorative maintenance as the corresponding residential systems.  You will also need to pay attention to exterior finishes and weatherstripping.  Door and cabinet hinges and latches may need to be lubricated and adjusted from time to time.

Trailer on!