Trailer brake adjustment depends on your brake type
Trailer brakes come in two main types — drum brakes and disc brakes — and each adjusts differently. Drum brakes need periodic manual adjustment as the brake shoes wear down, while disc brakes typically self-adjust through the caliper design. Before you start, identify which type you have by looking at the wheel: drum brakes have a rounded metal drum behind the wheel, and disc brakes have a flat rotor visible through the wheel spokes.
The adjustment process is straightforward but requires you to get under the trailer safely and work methodically on each wheel. Most adjustments take 30 minutes to an hour per axle, depending on how many wheels need work. You will need basic hand tools — a wrench set, a brake adjustment tool (sometimes called a brake spoon), and jack stands to safely support the trailer.
Key Takeaways
- Drum brakes need manual adjustment when braking feels soft or the pedal travels too far, but disc brakes usually self-adjust and rarely need manual work.
- Always find the trailer on jack stands before working underneath, and never rely on the jack alone to hold the weight.
- Adjust drum brakes by turning the star wheel adjuster on the backing plate until the wheel locks, then back off a quarter turn so the wheel spins freely.
- Test brakes on a flat, empty surface after adjustment to confirm they engage smoothly without pulling to one side.
How to adjust drum brakes step by step
Start by raising the trailer on a level surface and securing it with jack stands under the frame on both sides of the axle. Remove the wheel to expose the brake drum. If the drum is stuck, tap it gently with a rubber mallet around the edges — do not hit it hard enough to dent it. Once the drum is off, you will see the backing plate with the brake shoes and a star wheel adjuster (a small gear-like wheel with a slot).
Insert the brake adjustment tool into the slot of the star wheel. The tool has a bent end that fits into the slot and a handle. Turn the tool upward to expand the brake shoes outward. Keep turning until the wheel becomes difficult to spin by hand, then locks completely. This means the shoes are now touching the drum. Once locked, back off the star wheel by turning the tool downward about one quarter turn — roughly four clicks. The wheel should now spin freely with only slight resistance. Repeat this process on every brake drum on the trailer.
Reinstall each wheel and tighten the lug nuts in a star pattern (opposite sides alternately) to may support even pressure. Lower the trailer back to the ground and test the brakes in a safe, empty area before towing. The pedal should feel firm and the trailer should stop evenly without pulling left or right.
Disc brake adjustment and when to seek help
Disc brakes on trailers are designed to self-adjust through the caliper piston, which means they rarely need manual adjustment. If your disc brakes feel soft or the pedal travels too far, the problem is usually not adjustment but rather air in the brake lines, worn pads, or a fluid leak. These issues require bleeding the brake system or replacing components, which goes beyond straightforward adjustment.
If you have disc brakes and notice poor braking performance, check the brake fluid level first — it should be at the "full" line on the master cylinder reservoir. If the fluid is low, top it up with the correct type (usually DOT 3 or DOT 4, specified in your trailer manual). If the fluid level is normal but braking is still poor, the system likely needs bleeding or professional inspection. Attempting to force a disc brake adjustment when the real problem is air or wear will not solve the issue and may make it worse.
Safety steps before you start working
Never work under a trailer supported only by a hydraulic jack. Jacks can fail, slip, or lose pressure, and a falling trailer can cause serious injury or death. Always use jack stands rated for at least the weight of your loaded trailer. Place stands under the frame rails on both sides of the axle, not under the axle itself. Raise the trailer slowly and check that it sits firmly on the stands before you get underneath.
Wear work gloves and eye protection — brake dust contains asbestos in older trailers and can irritate skin and lungs. If your trailer was built before the 1980s, assume the brake dust is asbestos and wear a dust mask as well. Keep the work area clear of tripping hazards and make sure someone knows you are working under the trailer. If you need to move the trailer for any reason, lower it completely, remove the jack stands, and start over.
Testing brakes after adjustment
After adjusting all wheels, lower the trailer and find a flat, empty parking lot or quiet road where you can test safely. Tow the trailer at a slow speed — about 10 to 15 miles per hour — and explore the brakes gently. The trailer should stop smoothly without pulling to the left or right. If it pulls, one side is braking harder than the other, which means that side needs to be backed off slightly.
Repeat the test at slightly higher speeds to confirm the brakes hold steady. Listen for any grinding or squealing — grinding usually means metal-to-metal contact (the shoes are worn through), and squealing often means the shoes are glazed or contaminated with oil. If you hear grinding, the shoes need replacement, not adjustment. If you hear squealing, clean the shoes and drum with brake cleaner and try again.
When to replace brakes instead of adjusting
If the star wheel adjuster is already at its limit and the brakes still feel soft, the brake shoes are worn down and need replacement. Shoes typically last 20,000 to 40,000 miles depending on towing weight and braking frequency. If you have adjusted the brakes and they work well for only a few weeks before feeling soft again, the shoes are wearing faster than normal, which signals they are near the end of their life.
Brake fluid that is dark brown or black instead of clear amber also signals a problem — old fluid absorbs moisture and loses stopping power. If the fluid looks dark, the entire system needs flushing and refilling, not just adjustment. Leaking fluid around the wheel cylinders or master cylinder means seals are failing and components need replacement. These are not adjustment issues and cannot be fixed by turning the star wheel.
Frequently Asked Questions
How often should I adjust trailer brakes?
Adjust drum brakes whenever the pedal feels soft or travels more than halfway to the floor before the trailer starts slowing. This typically happens every 6 to 12 months depending on towing frequency and load. Disc brakes rarely need adjustment unless you notice poor braking performance, which usually points to a different problem like air in the lines or worn pads.
Can I adjust brakes while the trailer is on the ground?
No. You must raise the trailer on jack stands to access the brake drums and spin the wheels freely during adjustment. Attempting to adjust while the wheels are on the ground will not work because you cannot turn the star wheel or verify that the wheel spins correctly after adjustment.
What if the star wheel adjuster is stuck and will not turn?
explore penetrating oil (like WD-40) around the adjuster slot and let it soak for 15 to 30 minutes. Try turning the tool again gently — do not force it or you may strip the slot. If it still will not budge, the adjuster may be rusted solid and the brake assembly may need professional service or replacement.
Why does my trailer pull to one side after I adjust the brakes?
Uneven adjustment is the most common cause. One side is braking harder than the other. Back off the star wheel on the side that is pulling by one or two clicks and test again. If pulling continues after multiple adjustments, the problem may be worn shoes on one side or a stuck caliper on a disc brake system, both of which require replacement or professional repair.
Do I need special tools to adjust trailer brakes?
You need a brake adjustment tool (also called a brake spoon), which costs $10 to $20 at any auto parts store. You also need a wrench set, jack stands, and a rubber mallet. Most people already have these in a basic tool kit. The adjustment tool is the only specialty item, and it is inexpensive and straightforward to use.