The short version
- A drum in hat parking brake hides a small drum brake inside the rear rotor.
- It is why a rear rotor will not come off even with every bolt out and the handbrake released.
- Worn shoes cut a ridge in the drum, and the shoes have to be backed off through an access hole.
- Find the hole first. It is either in the rotor face or behind the backing plate.
The caliper is off, the bracket is off and the parking brake lever is down. The rotor still will not move.
The obstruction is usually a drum in hat parking brake, and hitting it harder will not help.
What a drum in hat parking brake is
The rotor hat is machined as a small drum on its inside face. Two curved shoes sit inside it on their own backing plate.
The foot or hand parking brake expands those shoes against that drum. The service brake caliper has nothing to do with it.
So releasing the parking brake relaxes the shoes but does not retract them past the wear they have created.
Why the rotor still will not move
The shoes only ever contact a band in the middle of the drum. Over years they wear a groove, leaving a raised ridge at the open edge.
The rotor cannot slide over that ridge with the shoes still adjusted out. Pulling harder changes nothing.
This is also why a rotor that is genuinely just corroded feels different. Corrosion resists everywhere; a ridge stops it dead at one point.
The corrosion version is on the stuck rotor page.
Finding the adjuster
| Location | How to use it |
|---|---|
| Hole in the rotor face | Rotate the rotor until it lines up with the star wheel |
| Hole in the backing plate | Reach in from behind, often with a rubber plug |
| Hole behind a wheel stud | Common, and easy to miss |
| No hole at all | The shoes retract by cable slack instead |
Turn the star wheel to contract the shoes. Which direction depends on the side of the car, so if it gets tighter, go the other way.
A parking brake cable that has seized or stretched can hold the shoes out even with the lever fully down.
A rusted cable is common on older cars and it makes the adjuster fight you for no reason.
While it is open
The drum surface, the shoes and the springs are all visible exactly once, during a job like this.
Look for grease on the linings, which points at a failed seal, and for shoes worn near their rivets.
Reading grease where it should not be is on the grease leak page. The wider checklist is on the checks page.
Putting it back
Back the shoes right off to get the rotor on. Then expand them until it just drags, and back off a click or two.
Do the same on the other side. Uneven parking brakes pull the car sideways when they are applied on a slope.
The equivalent job on a full drum rear is on the drum brakes page.
Working through it
- Release the parking brake fully and check the cable is genuinely slack.
- Find the access hole, in the rotor face or the backing plate.
- Back the star wheel off until the shoes are clear of the ridge.
- Remove the rotor, using jacking bolts if it is also corroded.
- Readjust both sides after reassembly, to a light even drag.
Common questions
What is a drum in hat parking brake?
A small drum brake built into the inside face of the rear rotor. It is worked by the parking brake, not the caliper.
Why will my rear rotor not come off?
The shoes have worn a groove in the drum, leaving a ridge the rotor cannot pass. Back them off through the adjuster.
Where is the adjuster?
Behind an access hole in either the rotor face or the backing plate, sometimes hidden behind a wheel stud.
Which way do I turn the star wheel?
It depends on the side of the car. If the shoes get tighter, reverse the direction.
Do I need to adjust it afterwards?
Yes, and on both sides. Uneven adjustment makes the car pull when the parking brake is applied.
Could it be the cable rather than the adjuster?
Often on an older car. A seized cable holds the shoes out even with the lever down.
Is this the same as a rear drum brake?
No. This is a parking brake only, and the service braking is still done by the caliper on the rotor outside it.