Your trailer has been sitting all winter. Before you hook up and hit the road, here’s what you need to go through so you’re not dealing with a breakdown, a ticket, or worse.
This is a complete pre-season trailer inspection checklist covering frame integrity, coupler and tongue, wheel bearings, brakes, tires, lights, and suspension. It includes Michigan-specific legal requirements, maintenance intervals, and what to look for before your first tow of the year. If you don’t want to do it yourself, we offer free trailer inspections at our shop in Flint, MI.
Michigan winters are hard on everything, and trailers are no exception. After months of freezing temps, moisture, road salt, and just sitting there doing nothing, things deteriorate. Every spring, our shop in Flint sees trailers come in from Burton, Grand Blanc, Davison, Fenton, and all over Genesee County with problems that a quick inspection would have caught before the first trip of the year.
Some of this you can handle in your driveway with basic tools and a jack. Some of it needs a shop with the right equipment. Either way, knowing what to look for is what keeps you safe and keeps a small fix from turning into a big bill.
Frame and Structural Integrity
The frame is everything. If the frame is compromised, the rest of the inspection doesn’t matter much.
Walk the entire frame from the tongue to the tail, both sides, and get underneath it. You’re looking for cracks in the welds, rust that’s gone past surface level, bent or bowed crossmembers, and any deformation at the high-stress points. That means the spring hangers, the coupler mount, and where the axle bolts to the frame.
The tongue and coupler area take the most stress during towing, and that’s where fatigue cracks tend to show up first. If you see a crack at a weld joint, don’t tow the trailer. Get it to a certified welder and have it evaluated before you put it on the road.
Some surface rust on a Michigan trailer is just reality. That’s not what we’re worried about. What you’re watching for is structural rust, where the metal has actually lost thickness. Flaking steel, scaling, and rust-through holes. Take a screwdriver and poke any spots that look suspect. If the screwdriver goes through, or the metal crumbles, that section needs to be cut out and replaced by a fabrication shop. A coat of paint isn’t going to fix that.
What to look for
- Cracks at weld joints, especially near the tongue and spring hangers
- Rust that has eaten through the metal or thinned it out
- Bent or bowed crossmembers
- Loose or missing bolts at structural connections
- Deformation or flex that wasn’t there before
Coupler, Tongue, and Safety Chains
The coupler is what keeps your trailer attached to your truck. If it’s worn out or damaged, you’ve got a serious problem. Safety chains help, but at highway speed they’re a last resort, not a safety plan.
Open and close the coupler latch a few times. It should snap into position firmly with no slop or play. If the latch is stiff, corroded, or won’t fully engage, it needs to be cleaned and lubed or replaced entirely. Look for visible cracks on the coupler body, particularly around the pivot point and the weld where it meets the tongue.
Run the tongue jack all the way up and all the way down. Check for bent tubes, a cracked foot plate, and whether the gear mechanism operates smoothly. On screw-type jacks, make sure the threads aren’t stripped. Hit all the moving parts with some grease while you’re at it.
Michigan law requires safety chains on all towed vehicles, in addition to the coupler connection. Check your chains for stretched or damaged links and make sure the hooks are solid. The chains should cross under the tongue in an X-pattern so they’ll cradle the tongue if the coupler ever separates. Each chain needs to be rated for the full loaded weight of the trailer.
You can find the full Michigan vehicle code covering trailer safety equipment and weight classifications at MCL 257.688 on the Michigan Legislature website.
What to look for
- Coupler latch that won’t fully engage or has too much play
- Cracks or heavy corrosion on the coupler body
- Bent or damaged tongue jack
- Safety chains with worn, stretched, or cracked links
- Missing or non-functional breakaway switch (required on trailers with electric brakes)
Wheel Bearings: The Most Skipped Maintenance on Any Trailer
If there’s one thing on this list that people ignore until it’s too late, it’s the wheel bearings. And it’s the one thing most likely to leave you sitting on the shoulder of I-69 waiting for a tow.
Dexter, which is the largest trailer axle manufacturer in North America, recommends a full bearing repack every 12 months or 12,000 miles, whichever comes first. And the key word there is “whichever.” A trailer that’s been parked in your driveway all winter isn’t safe just because it didn’t go anywhere. It might actually be worse off than one that was towed regularly.
Here’s why. When a trailer sits, moisture and condensation collect inside the hub. That moisture pits the bearings and the races they ride on. Then you hook up in April and head down the highway, and those pitted, corroded surfaces start generating way too much heat and friction. A seized bearing can fuse the hub to the spindle. It can cause a wheel to come off at speed. It can actually start a fire. We’ve seen all three. And every single one of them could have been prevented with an annual repack that runs somewhere between $50 and $100 per axle.
One thing we want to clear up: if you have EZ-Lube zerks on your axles, pumping grease through the fitting is not the same thing as a repack. EZ-Lube was originally designed for boat trailers that get dunked in the water at the ramp. It pushes out contaminated grease between proper repacks. But it does not replace pulling the hub off, cleaning everything out, inspecting the bearings and races, putting in a fresh seal, and setting the bearing nut to the right tension. Those are different jobs.
Before your first tow of the season, jack up each wheel and spin it by hand. Listen for any grinding, rumbling, or roughness. Then grab the wheel at the top and bottom and try to rock it. There should be very little play. If you feel grinding, hear noise, or the wheel wobbles, don’t tow the trailer until the bearings have been looked at.
What to look for
- Grinding, rumbling, or rough feel when spinning the wheel by hand
- Wobble or excessive play when rocking the wheel top to bottom
- Grease leaking from the hub or showing up on the inside of the wheel
- Blue or brown discoloration on the hub or spindle (heat damage)
- Any sign of a previous failure like a scored spindle or melted grease
Need a bearing repack before towing season? We handle bearing service, inspection, and replacement at our shop on Lapeer Road in Flint. Call (810) 407-7585 to schedule.
Trailer Brakes: What Michigan Law Requires and How to Test Yours
Michigan requires independent braking systems on any trailer with a gross weight over 3,000 lbs. Once you get above 5,500 lbs, the brakes need to be strong enough to control, stop, and hold the trailer on their own.
If you have electric brakes, start with the brake controller inside your tow vehicle. Hook up the trailer, hit the manual override on the controller, and walk around back. You should hear and feel the brakes grabbing on each wheel. If one side isn’t doing anything, you’ve probably got a wiring issue, a dead magnet, or a broken connection at that wheel.
Pull the drums off and look at the brake shoes. The lining should have at least 1/16″ of material above the rivets. If it’s thinner than that, they need to be replaced. Also check for oil or grease on the linings. That means a bearing seal has failed and grease got onto the brakes. You can’t clean contaminated shoes well enough to trust them. Replace them.
While the drums are off, look at the magnets on each brake assembly. The contact surface should be smooth with a slight concave wear pattern. If you see gouges, deep grooves, or the magnet is worn down to the coil windings, it’s time for new ones. A worn out magnet can’t generate enough friction against the drum to actually stop anything.
For surge brakes (hydraulic), check the master cylinder fluid level and look over the actuator for any damage. Push the coupler in by hand. You should feel solid resistance as the hydraulic system builds pressure. If it pushes in easy with no resistance, you’re looking at a leak, low fluid, or a bad master cylinder.
What to look for
- Brake shoes worn below 1/16″ above the rivets
- Grease or oil contamination on the brake linings
- Worn or damaged brake magnets
- Drums that are scored, cracked, or out of round
- Electric brakes that aren’t engaging on one or more wheels
- Low fluid or spongy feel on surge brake systems
- Corroded or damaged brake wiring and connectors
Tires: Age Matters More Than Tread Depth
This one surprises a lot of people. Trailer tires fail differently than the tires on your truck. They don’t self-correct like steered tires do. They sit under a static load for long stretches. And the sidewalls take a beating from UV and weather even when the trailer isn’t moving. When they go, it’s usually a blowout, not a slow leak.
Check the DOT date code on each tire. There’s a four-digit number stamped into the sidewall. “2219” means it was made in the 22nd week of 2019. Most tire manufacturers say you should replace trailer tires every 5 to 6 years no matter how much tread is left. The rubber compounds break down from UV, ozone, and temperature swings even when the trailer is just sitting there. A tire with good tread that’s 8 years old is a blowout waiting to happen. We’ve seen it more times than we can count.
Michigan requires a minimum tread depth of 2/32″ for trailers on the road. The penny test works fine for this. Stick a penny in the tread groove with Lincoln’s head pointing down. If you can see the top of his head, you’re at or below the legal limit and the tire needs to go.
Check pressure with an actual gauge, not just by looking at the tire. Inflate to the pressure stamped on the tire sidewall. Not the trailer’s placard, not whatever your truck runs. The tire’s own rated pressure for its load rating. Running trailer tires underinflated is the number one cause of blowouts because of the heat it generates.
Go over all the sidewalls looking for cracking, bulging, or weathering. And check the tread for uneven wear, which can point to axle alignment issues, overloading, or a bearing that’s on its way out.
What to look for
- Tires older than 5 to 6 years (check the DOT date code on the sidewall)
- Tread depth below 2/32″
- Sidewall cracking, bulging, or dry rot
- Uneven tread wear patterns
- Wrong tire pressure (use a gauge, don’t eyeball it)
- Damaged or corroded valve stems
Lights and Electrical: Michigan Requirements by Trailer Weight
Wiring problems are the single most common issue we see on trailers coming out of winter storage. They’re also one of the first things law enforcement will notice if they pull you over.
Michigan’s lighting requirements depend on what the trailer weighs. Here’s the short version: Every trailer on the road needs working taillights and reflectors. Over 2,500 lbs and you also need turn signals and two red or amber stop lights visible from 100 feet. Over 3,000 lbs adds amber clearance lights on the front, red clearance lights on each side near the rear, and two red clearance lights on the back. You also need working brakes and a breakaway switch at that weight. The full breakdown is in MCL 257.688.
Plug the trailer into your tow vehicle and have someone stand behind it while you cycle through every function. Running lights, left turn, right turn, brakes, reverse if you have it. Test them all.
Nine times out of ten, the problem is a corroded ground connection. Trailer lights ground through the frame, and any corrosion between the ground point and the light creates resistance that dims the circuit or kills it entirely. Scrape the ground points down to clean bare metal, put some dielectric grease on there, and tighten them back up. That fixes the majority of trailer lighting headaches.
If you’ve been chasing electrical gremlins and nothing seems to stick, consider converting to a sealed LED lighting system. LEDs pull less current, they’re brighter, they last way longer, and they’re sealed against water intrusion. It’s one of the best upgrades you can do to any trailer, and the cost is pretty reasonable for the problems it solves.
What to look for
- Taillights, brake lights, or turn signals not working
- Dim or flickering lights (almost always a ground issue)
- Cracked or water-filled light housings
- Corroded plug connectors
- Wiring that’s chafed, pinched, or hanging loose along the frame
- License plate light not working
Springs, Hangers, and Suspension Components
The suspension absorbs the punishment so the frame and your cargo don’t have to. After a Michigan winter with all the freeze-thaw cycles and road salt, spring shackles, U-bolts, and equalizers take a real beating.
Check your leaf springs for cracked, broken, or separated leaves. A broken leaf spring makes the trailer sit crooked and can throw the axle out of alignment, chew up tires, and make the whole rig handle dangerously. Look at the spring hangers too. Those are the brackets welded to the frame that hold the spring eyes. If the welds on those are cracked or the hangers are bent, the whole suspension can shift under load.
Check the U-bolts that clamp the axle to the springs. They need to be tight and in decent shape. Loose U-bolts let the axle move around, which kills alignment, tears up tires, and makes the trailer track off to one side.
If your trailer runs torsion axles, look over the mounting brackets for cracks and inspect the rubber cartridge housing. Torsion axles don’t have springs you can see, but the internal rubber cords do break down over time, and cold winters speed that process up.
Grease all the suspension pivot points while you’re at it. Spring eyes, shackle bolts, equalizer pins. Dry pivots wear out fast and can seize up, which just puts more stress on the springs and the frame.
What to look for
- Cracked, broken, or separated leaf springs
- Bent or cracked spring hangers
- Loose or corroded U-bolts
- Trailer sitting unevenly, with one side lower than the other
- Worn shackle bolts or equalizer pins
- Cracks or damage on torsion axle mounting brackets
Final Walk-Around and Test Drive
Once you’ve been through each system, step back and look at the trailer as a whole with fresh eyes.
Is it sitting level from side to side? If one side is lower, you might have a broken spring, a low tire, or a bad torsion arm. Check the tongue height when it’s coupled to your tow vehicle. The trailer should ride level or just slightly nose-down. If it’s pointing way up or way down, you’re putting extra stress on the coupler, messing with your braking, and making the trailer unpredictable to tow.
Look over all the tie-down points, stake pockets, and D-rings. If the trailer has a wood deck, poke any sketchy-looking areas. Soft or spongy spots mean those boards are rotting and need to be replaced. Check ramps and tailgates for bent hinges or busted latches.
Then take it for a short drive. A mile or two at low speed in a quiet area. Hit the brakes a few times. Listen for anything that sounds wrong. After about a mile, pull over and carefully touch each hub with the back of your hand. They should be warm. That’s normal friction. But if one hub is noticeably hotter than the others, you’ve got a bearing problem and that wheel needs attention before you do any real towing.
When to Bring It to a Shop
You can handle a lot of this yourself if you’re comfortable under a trailer with a jack and some basic tools. But bearing repacks, brake work, frame crack repairs, axle jobs, full rewires, and suspension repairs are shop work. Doing those wrong tends to create bigger problems than whatever you started with.
If the trailer has been sitting for more than one season, if you bought it used and don’t know its history, or if your inspection turned up something that doesn’t look right but you’re not sure what it means, just bring it in. A professional inspection doesn’t take long and it catches the stuff that costs a couple hundred now but a couple thousand later if it lets go on the highway.
We work on trailers from all over Mid-Michigan. Flint, Burton, Grand Blanc, Fenton, Davison, Lapeer, Flushing, Swartz Creek, Clio, and everything in between. Whether it’s a bearing repack, a frame weld repair, a complete brake job, or a wiring overhaul, our trailer center handles it all in one shop.
Common Trailer Inspection Questions
Every 12 months or 12,000 miles, whichever comes first. That recommendation comes from Dexter, the largest trailer axle manufacturer in North America. A trailer that has been sitting all winter still needs a repack before the first tow of the season because moisture and condensation collect inside the hub and pit the bearings even when the trailer isn’t moving.
Michigan requires an independent braking system on any trailer with a gross weight over 3,000 lbs. Above 5,500 lbs, the brakes must be able to control, stop, and hold the trailer on their own. The full requirements are in MCL 257.688 on the Michigan Legislature website.
Most tire manufacturers recommend replacing trailer tires every 5 to 6 years regardless of tread depth. The rubber compounds break down from UV exposure, ozone, and temperature changes even when the trailer is parked. Check the four-digit DOT date code on the sidewall to find the manufacturing date.
You can handle most of the visual and mechanical checks in your driveway with a jack, basic hand tools, and a tire gauge. That includes frame inspection, tire checks, light testing, and a basic wheel bearing spin test. Bearing repacks, brake work, structural weld repairs, and suspension work should be done by a qualified shop with the right equipment.
At Iron Mann Industries we offer a complimentary multi-point trailer inspection at our Flint shop. No charge and no obligation. We go through the frame, axles, bearings, brakes, lights, suspension, and overall condition and tell you exactly where it stands.
Free Trailer Inspection. No Charge, No Obligation.
We offer a complimentary trailer safety inspection at our shop in Flint. We go through the frame, welds, axles, bearings, brakes, lights, suspension, and overall condition. If it all checks out, you’re good to go. If we find something, we’ll show you what it is and tell you what it’ll take to fix it. No games, no pressure. We’ve been doing this for over 20 years and we’d rather see you towing safe than towing at all.
Schedule your free inspection or call us at (810) 407-7585.
Quick Reference: Pre-Season Trailer Inspection Checklist
Print this out or save it on your phone. Walk around the trailer and go through each one before your first tow of the year.
Frame: Walk the whole thing. Look for weld cracks, structural rust, bent crossmembers, and loose bolts.
Coupler and Tongue: Test the latch. Check the safety chains. Run the tongue jack up and down. Make sure the breakaway switch works.
Bearings: Spin each wheel by hand and listen. Rock each wheel top to bottom and check for play. If it’s been more than 12 months, get them repacked.
Brakes: Test engagement on every wheel. Pull the drums and check shoe thickness. Look for grease on the linings. If you have surge brakes, test the actuator by hand.
Tires: Read the DOT date code (replace anything over 5 years). Measure tread depth. Inflate to the pressure on the tire sidewall. Inspect the sidewalls for cracks.
Lights: Plug in and test every function. Clean your grounds. Replace any cracked or flooded housings. Don’t forget the license plate light.
Suspension: Check leaf springs for cracks. Make sure U-bolts are tight. Grease the shackle bolts and equalizer pins. See if the trailer sits level side to side.
Test Drive: Take it a mile or two at low speed. Test the brakes a few times. Then check hub temps by hand. Warm is fine. Hot means trouble.
Or call (810) 407-7585 to set up a time.
