What to check on a tandem-axle travel trailer, and when to change it
The short answerBefore every trip, set the tire pressure, test the brakes and breakaway switch, check the lights and torque the lug nuts. Every 12 months or 12,000 miles, have the wheel bearings cleaned and repacked and the brakes inspected. Trailer tires commonly age out in 3 to 5 years, whatever the tread looks like. Call (805) 745-1992.
See our services on a 3D trailer
Pick one of our services, or start with what your trailer is doing. All 20 parts are named, with what to check and when to change each one.
It loads only when you ask, so this page stays fast.
Drag to turn the trailer. Pinch, or hold Ctrl and scroll, to zoom. Pick a service and the trailer turns see-through so its parts stand out.
Start here
Pick a service
Choose one of our services and the trailer shows every part it covers. Not sure which? Switch to “By symptom” and start with what it’s doing.
What to ask about, and when
Pick the point closest to where you are. You’ll get the list of what usually comes up around then, and you can show it on the trailer.
Last updated October 19, 2026.
This is a simplified model, not a factory drawing. Part positions are approximate and intervals are typical ranges. Your owner’s manual, your service records and how you drive decide the real schedule. The model is a typical 26-foot tandem-axle trailer. Axle positions and layout vary by maker. Intervals come from axle, tire and trailer makers’ published guidance, listed below. We’ll tell you what we see when you bring it in.
Open a system to read about its parts: what each one does, what to check, when to change it, and the service that covers the work.
Hitch and coupling 4 parts
1Coupler and hitch ball
The coupler on the front of the A-frame clamps over the ball on your tow vehicle. It is the one solid connection between the two.
What to check
The ball size is stamped on the coupler. Travel trailers use either a 2 inch or a 2-5/16 inch ball, and the ball must match. Look for a worn or loose latch, cracks around the coupler welds and a missing latch pin. A light film of grease on the ball helps.
When to change it
There is no set interval. Replace a coupler that is cracked, bent or will not latch firmly. Check it before every trip.
Ask us about coupler and hitch work on your trailer.
2Safety chains
Two chains tie the trailer to the tow vehicle if the coupler ever comes off the ball.
What to check
Cross the chains under the tongue so they form a cradle. Ford’s towing guide says this keeps the tongue from hitting the ground if the trailer separates. Leave enough slack to turn, and keep them from dragging. Look for stretched links, worn hooks and missing hook latches.
When to change it
Replace chains or hooks that are worn, stretched, rusted thin or have dragged on the road. Some trailers have had recalls for safety chain attachment, so check your VIN at nhtsa.gov/recalls.
Ask us about safety chain replacement on your trailer.
3Weight-distribution hitch and sway control
Spring bars shift some of the tongue weight forward to the tow vehicle’s front axle and back to the trailer’s axles. Sway control resists the trailer wagging side to side.
What to check
Look for cracked welds, worn bar sockets, loose head bolts and missing clips. The truck should sit close to level when hooked up. Aim for a tongue weight of 10 to 15 percent of the loaded trailer weight. Too little tongue weight is a common cause of sway.
When to change it
There is no set interval. Lubricate and adjust it the way the hitch maker says. Have the setup checked again when you change tow vehicles or how you load the trailer.
Ask us about hitch setup for your truck and trailer.
4Tongue jack and stabilizer jacks
The tongue jack lifts and lowers the front of the trailer for hitching and leveling. The four corner stabilizer jacks steady the trailer once it is parked.
What to check
The tongue jack should run smoothly with no grinding and should hold its height. Check the foot or wheel. Stabilizer jacks only steady the trailer. Jayco’s manual warns against using them to level the RV because they are not built to carry its weight. Raise them all before you move.
When to change it
There is no set interval. Clean and lubricate the screws as your manual says. Replace a jack that binds, slips or is bent.
Ask us about jack repair or replacement on your trailer.
Brakes 3 parts
5Electric drum brakes, shoes and magnets
Each wheel has a drum brake. Current from the tow vehicle energizes a magnet inside the drum, the magnet grabs the drum face and a lever pushes the shoes out.
What to check
Test the brakes at walking speed with the controller’s hand lever before every trip. Grabbing, pulling to one side or weak braking all need a look. Brakes without self-adjusters need adjusting by hand. Dexter says after the first 200 miles and then about every 3,000 miles. Self-adjusting brakes need no manual adjustment. If the trailer brakes do not work, don’t tow it.
When to change it
Dexter says to inspect linings, drums and wiring every 12 months or 12,000 miles and the magnets every 6 months or 6,000 miles. Replace shoes worn to 1/16 inch or less, or soaked with grease. Replace magnets that are worn unevenly or show the coil.
A cable runs from a small switch on the trailer to the tow vehicle. If the trailer comes loose, the cable pulls a pin and the trailer’s own battery applies the brakes.
What to check
Dexter’s schedule says to check the battery charge and switch operation every use. With the 7-way cord unplugged from the tow vehicle, pull the pin and try to roll the trailer. The wheels should drag. Put the pin straight back in so you don’t drain the battery. Clip the cable to the tow vehicle, never to the safety chains or the ball.
When to change it
Replace the switch if the pin is corroded or the brakes do not apply. Replace the battery when it will no longer hold a charge, commonly every 3 to 5 years.
The controller in the cab decides how much current goes to the trailer brakes each time you press the pedal.
What to check
The trailer should slow with the truck, without jerking and without pushing. Set the gain with the trailer loaded, following the controller maker’s steps. A warning on the dash or no trailer braking with the hand lever points to wiring or controller trouble.
When to change it
No set interval. Dexter’s schedule says to check the controller for correct amperage and modulation every 6 months or 6,000 miles. Reset the gain when the trailer’s load changes a lot.
Ask us about brake controller checks and wiring on your tow vehicle.
Trailer tires are marked ST for special trailer. They are built with stiff sidewalls to carry load and resist sway. The four of them carry the whole trailer.
What to check
Check pressure cold before every trip. Use the figure on the trailer’s tire placard. Carlisle says to keep ST tires at the maximum pressure on the sidewall. Look for cracks, bulges and cuts. Read the four-digit date code. Most ST tires are rated for 65 mph unless marked higher. Never go down a load range from what the placard calls for.
When to change it
Carlisle says 3 to 5 years is the average life of a trailer tire regardless of mileage, and to replace at five years even with tread left. Dexter says at least every five years. Replace sooner for cracking, bulges or uneven wear.
The spare gets you off the shoulder after a flat. It sits out in the sun all year, so it ages even if it never touches the road.
What to check
Check its pressure when you check the other four. Look for sidewall cracks and read the date code. Make sure the mount is tight and that you carry a jack and lug wrench that fit the trailer.
When to change it
Replace it on age like the other tires, commonly by 5 to 6 years. A cover slows sun damage.
The lug nuts clamp each wheel to its hub. Trailer wheels see heavy side loads in turns, so the nuts can work loose.
What to check
Torque the nuts with a torque wrench in a star pattern. Dexter says to tighten in three stages, then re-torque after the first 10, 25 and 50 miles any time a wheel has been off. Dexter’s chart lists 100 to 120 foot-pounds final torque for most 14 to 16.5 inch wheels. Use your trailer maker’s figure. Look for cracks, rust streaks from the nuts and bent rims.
When to change it
No set interval. Dexter’s schedule lists a torque check every 3 months or 3,000 miles and a wheel inspection every 6 months or 6,000 miles. Replace cracked or bent wheels and damaged studs.
Each hub turns on two tapered roller bearings packed in grease. A seal at the back keeps the grease in and off the brake shoes.
What to check
After a drive, carefully feel each hub. One much hotter than the others needs attention. Jack a wheel and feel for looseness or a rough, rumbling spin. Grease slung on the inside of a wheel means a failed seal.
When to change it
Dexter says to clean, inspect and repack the bearings every 12 months or 12,000 miles, and to replace the seals whenever they are removed. A trailer that sits still needs it by the calendar.
Ask us about a bearing repack when we have the drums off for a brake inspection.
Each axle rides on a leaf spring per side. A rocking equalizer between the two springs shares bumps between the axles. Shackle links and bushings let it all move.
What to check
Look for a broken or flattened leaf, a trailer that sits low on one side, and shackle links with worn or oval bolt holes. Check that U-bolts are tight. Squeaks and clunks over bumps point to worn bushings. If there are grease fittings, Dexter’s schedule says to grease them every 3 months or 3,000 miles.
When to change it
No set interval. Dexter says to inspect suspension parts every 6 months or 6,000 miles and springs and hanger welds every 12 months or 12,000 miles. Replace worn bushings, links and sagging springs.
Ask us about spring, equalizer and bushing work on your trailer.
Two straight tube axles carry the hubs and brakes. They also set the direction each tire points, so a bent axle shows up as tire wear.
What to check
Read the tires. Dexter’s wear chart says toe wear means a tire is not tracking in the same direction as the others, and cupping points to balance or bearing trouble. A bent axle or a shifted spring seat can follow a curb strike or overloading. Check the weight sticker and stay under the axle ratings.
When to change it
No set interval. Have the axles measured if tires wear unevenly or the trailer tracks to one side.
Ask us about checking trailer axle alignment and uneven tire wear.
The 7-way plug carries ground, brake power, tail lights, left and right turn and stop lights, a 12-volt charge line and reverse lights from the tow vehicle to the trailer.
What to check
Look for green or bent blades in the plug, a cracked housing and a cord that has dragged on the road. Lights that flicker or brakes that cut in and out very often trace to a poor ground or a corroded plug. Look along the axles for chafed brake wires.
When to change it
No set interval. Dexter says to inspect trailer brake wiring for bare spots and fraying every 12 months or 12,000 miles. Replace a damaged plug or cord.
The trailer’s lights tell drivers behind you what you are doing. They include tail, stop and turn lights at the rear and clearance markers along the sides and corners.
What to check
With the trailer plugged in, have a helper watch while you work the running lights, both turn signals, brakes and hazards. Look for cracked lenses and water inside. A light that works when you wiggle it has a bad ground or socket.
When to change it
Replace bulbs, sockets or sealed lamps as they fail. Check them all before every trip.
Two steel rails and crossmembers carry the body. The A-frame at the front ties the rails to the coupler and takes all the pulling and braking loads.
What to check
Look underneath for rust flaking, cracked welds at the spring hangers and where the A-frame meets the main rails, and bent crossmembers. Check that the entry step and bumper are solid. Cracked paint in a line near a weld can be the first sign of a crack in the steel.
When to change it
No set interval. Clean and repaint surface rust. Have any crack looked at before you tow again.
Ask us about frame inspection and welding repairs.
Living systems 4 parts
1712-volt house battery
The house battery runs the lights, water pump, furnace fan and tongue jack when you are not plugged in. On many trailers it also powers the breakaway brakes.
What to check
Keep the terminals clean and tight. On a battery with removable caps, keep the water level above the plates with distilled water. Parasitic loads will flatten it in storage, so use the disconnect switch or a maintainer.
When to change it
Typically every 3 to 5 years for a lead-acid battery. Check your manual. Replace it when it will not hold a charge.
Ask us about testing your trailer’s house battery. Coach wiring beyond that is best with an RV specialist.
18Propane cylinders and regulator
Two cylinders on the A-frame feed the stove, furnace, water heater and fridge through a regulator and hoses.
What to check
Read the manufacture date stamped on each cylinder collar. Look for rust, dents and cracked hoses. If you smell gas, shut the cylinder valves, put out flames and get everyone out. Do not tow with a known leak.
When to change it
US DOT rules say a cylinder must be requalified within 12 years of its manufacture date before it can be refilled. After that the period depends on the method, and it is 5 years after a visual inspection. Have the system leak tested as your manual says.
Sealant along the roof edges and around every vent, the air conditioner and the windows keeps rain out of the walls. A small gap can let water into the roof and walls for months before you see it inside.
What to check
Look for cracks, gaps, shrinkage and sealant lifting at the edges. Keystone says to inspect roof seals at least every three months and other exterior seals at least twice a year. Inside, watch for stains and soft spots on the ceiling and around windows.
When to change it
Touch up or reseal as soon as you find a gap. Use the sealant your roof maker lists, because roof materials differ.
A fresh tank, 12-volt pump and water heater supply the sinks and shower. Gray and black tanks under the floor hold waste until you dump.
What to check
Look under the trailer for drips and for dump valves that weep. Listen for the pump cycling when no tap is open, which points to a leak. Follow your manual for sanitizing the fresh tank and for winterizing before a freeze.
When to change it
No set interval. Sanitize and winterize the way your owner’s manual says. Replace dump valve seals when they leak.
Walk around it once before every trip. Tick each item as you check it. Your ticks stay on your phone.
Tires. Tire pressure on the vehicle, and on the trailer if you’re towing, is in the normal range for the tires and never above the maximum on the sidewall.
Lights. Brake lights and turn signals work.
Instructions. You’ve read the user instructions and safety decals for the equipment.
Coupler. The coupler is tightened, locked and secure.
Safety chains. The chains have enough slack to make a sharp turn, but not so much that they drag on the ground.
Trailer brakes. If the trailer has brakes, the breakaway chain is attached correctly.
Want something checked before you go? Call and ask. Motorhomes need to call ahead.Call (805) 745-1992
Questions owners ask
How often should travel trailer wheel bearings be repacked?
Dexter Axle, which builds the running gear under many travel trailers, says to clean, inspect and repack the bearings every 12 months or 12,000 miles, whichever comes first. The grease seals are replaced whenever they are removed. Check the manual for your own axles.
How long do trailer tires last?
Carlisle says 3 to 5 years is the average life of a trailer tire regardless of mileage, and that tires should be replaced after five years even with tread left. Dexter says to replace trailer tires at least every five years. Age and sun do the damage, so read the date code on the sidewall.
What pressure should I run in ST trailer tires?
Use the cold pressure on the trailer’s tire placard. Carlisle’s guidance for ST tires is to keep them at the maximum pressure printed on the sidewall. On many travel trailers those two numbers are the same. Check them cold, in the shade, before every trip.
How fast can I tow on ST tires?
Carlisle says most ST trailer tires have a maximum speed rating of 65 mph unless the sidewall is marked higher. In California the law also sets a 55 mph limit for a passenger vehicle towing a trailer.
When do I need to re-torque trailer lug nuts?
Dexter says to torque the wheel nuts in three stages, then check and re-torque after the first 10 miles, 25 miles and 50 miles any time a wheel has been off. After that, check them periodically. Dexter’s schedule lists every 3 months or 3,000 miles.
How much tongue weight should a travel trailer have?
Trailer makers such as Jayco give a target of 10 to 15 percent of the loaded trailer weight on the hitch. Too little tongue weight is a common cause of sway. A weight-distribution hitch is typically needed on a trailer this size. Check your tow vehicle’s manual for its rule.
