How to Manually Adjust Electric Trailer Brakes β Star Wheel Procedure
Pull the rubber plug from the slot at the bottom of the backing plate. Insert a brake adjustment spoon or narrow flathead screwdriver and turn the star wheel to expand the shoes until the drum drags heavily. Back off 8β10 clicks until you get a slight, even drag. Replace the plug. Repeat on every wheel β always adjust both sides of an axle together.
When to Adjust
Per Dexter's official service manual, electric trailer brakes should be adjusted:
- After the first 200 miles of operation on new brakes β shoes and drums need to seat before the adjustment sticks
- Every 3,000 miles thereafter under normal use
- Any time braking feels weak and voltage and wiring checks out fine
- After replacing shoes, drums, or magnets β new parts change clearance
- Before any extended trip β a few minutes of adjustment is cheap insurance
Under-adjusted brakes are the single most common cause of weak trailer braking in the field. The magnet has to travel farther to contact the drum, reducing the force it can apply to the shoes. Many trailers with "bad brakes" just need adjustment.
What You Need
- Jack and jack stands β wheels must spin freely
- Brake adjustment spoon (Dexter # W80630) β the right tool for the job. A narrow flathead screwdriver works in a pinch but the spoon gives better control
- Flashlight β the slot is at the bottom of the backing plate and can be hard to see
Step-by-Step Adjustment Procedure
- Raise and Support the Trailer Safely
Jack the trailer until the wheel you're adjusting clears the ground. Place jack stands under the frame β never work under a trailer supported only by a jack. Confirm the wheel spins freely before you start.
- Find and Remove the Rubber Plug
Look at the bottom of the brake backing plate (6 o'clock position). There's a rubber plug covering the adjustment slot. Pry it out with a screwdriver and set it aside β you'll replace it when you're done to keep debris out of the brakes.
- Locate the Star Wheel
Some Dexter backing plates have two slots β the star wheel is only behind one of them. Shine a flashlight in and use a screwdriver to probe gently until you feel the toothed star wheel. On some assemblies you may need to try both slots. Once you find it, note which slot works.
- Expand the Shoes Until the Drum Won't Turn
Insert the brake spoon into the slot and engage the teeth of the star wheel. Turn it to push the shoes outward toward the drum. Spin the drum by hand periodically as you adjust. Keep turning until the drum won't rotate freely β the shoes are now pressing firmly against it. This is your starting reference point.
- Back Off Until You Have a Light, Even Drag
Now reverse direction on the star wheel β back the shoes off. Count your clicks. Back off 8β10 clicks and spin the drum again. You're looking for the drum to spin freely with just a light, consistent drag β you should be able to feel slight resistance but spin it without real effort. If you hear or feel no drag at all, go back in a couple clicks.
- Replace the Rubber Plug
Push the rubber plug firmly back into the slot. It keeps road grime, water, and debris out of the brake assembly and prevents the star wheel from vibrating out of adjustment over time.
- Repeat on Every Wheel β Both Sides at the Same Time
Always adjust both wheels on the same axle during the same session. Unequal adjustment side-to-side causes the trailer to pull during braking. On a tandem axle trailer, adjust all four wheels. Drop the trailer off the jack stands, hook it to the tow vehicle, and do a low-speed brake test before loading.
Which Direction to Turn β The Part Everyone Gets Wrong
The star wheel direction to expand the shoes is opposite on the driver's side vs. the curb side. This trips up a lot of people. Here's a simple rule:
| Side of Trailer | Direction to Expand (Tighten) | Direction to Back Off |
|---|---|---|
| Driver's side (left) | Rotate the bottom of the star wheel toward the rear of the trailer | Rotate bottom toward front |
| Curb side (right) | Rotate the bottom of the star wheel toward the front of the trailer | Rotate bottom toward rear |
If you're turning and turning and nothing is happening, you're going the wrong direction. Reverse and you'll feel it engage immediately.
Many Dexter backing plates are identical for both left and right sides β so they're manufactured with two adjustment slots. Only one slot gives access to the star wheel on any given assembly, depending on which side of the trailer it's installed on. If you probe one slot and find nothing, check the other one.
How to Tell If Your Adjustment Is Right
The correct adjustment feels like a very light, consistent drag when you spin the drum by hand β not locked, not completely free. Here's a quick reference:
| What You Feel | What It Means | Action |
|---|---|---|
| Drum won't turn at all | Too tight β shoes pressing hard on drum | Back off 3β4 more clicks |
| Very heavy drag, hard to spin | Still too tight | Back off 2β3 more clicks |
| Light, even drag β can spin with moderate effort | Correct adjustment | Done β replace plug |
| Spins completely freely, zero drag | Too loose β shoes not close enough to drum | Turn in 1β2 clicks |
| Grinding, scraping sound during spin | Possible shoe or drum damage β inspect before adjusting further | Pull drum and inspect |
A drum adjusted too tight will build heat rapidly during towing. Hot drums expand, which tightens the adjustment further, which builds more heat β a cycle that can score the drum, glaze the shoes, and destroy a perfectly good brake assembly in a single trip. If a wheel is noticeably hotter than the others after towing, loosen that brake.
After Adjustment β Break-In
If you replaced shoes or drums as part of this service, allow for a break-in period. New brake components need to wear into the drum surface before they reach full effectiveness. Dexter states this process requires more than 100 stops from 20 mph to fully complete. Braking will feel softer than normal until break-in is complete β this is expected.
