Quick answer
A cable drum is the grooved wheel fixed to each end of a garage door’s torsion shaft that winds the lift cable on as the door opens and pays it out as the door closes.
DASMA defines it as a grooved drum on the torsion spring shaft onto which the lifting cable winds when the door opens. Drum shape is matched to the door’s lift type: standard, high-lift or vertical-lift.
Quick facts
The key facts about Cable Drum, with sources:
- DASMA definition
- Grooved drum on the torsion shaft that winds the lift cable 1
- Mounted with
- Set screws to the shaft; one may secure the cable 1
- Standard residential size
- Commonly 4-inch drums (supplier figure) 7
- High-lift drum
- Contoured to balance a high-lift door 1
- Vertical-lift drum
- Changing-radius grooves to negate spring tension 1
- Under tension
- Always, from the springs 2
Key takeaways
- Two drums, one at each end of the torsion shaft, wind the lift cables.
- Drum size and shape are matched to the door’s height and lift type.
- Springs are sized for a specific drum; changing drums means re-checking springs.
- A cable off its groove, a cracked drum or loose set screws are serious.
- Drums are under spring tension: technician-only.
What a cable drum is
On a torsion spring door, the springs turn a shaft above the opening. At each end of that shaft sits a drum: a wheel with a spiral groove cut around it.
The lift cable from the bottom corner of the door is anchored in a slot on the drum, then winds into the groove as the shaft turns.
DASMA’s terminology defines a cable drum as a grooved drum, fitted on the torsion spring shaft, onto which the lifting cable is wound when the door is opened 1.
It also defines cable drum set screws, which attach the drum to the shaft, with one sometimes securing the cable 1, and a cable stop, a swaged fitting on the cable end that keeps it from slipping through the drum slot 1.
Heavier doors may use a ball bearing drum, which DASMA describes as a drum with a ball bearing for smoother operation 1.
How drums turn torque into lift
The drum is a lever. The spring’s torque turns the shaft; the cable leaves the drum at a certain radius; the pull on the cable equals torque divided by that radius. DASMA calls that the moment arm and defines pounds pull as torque divided by the drum’s moment arm 1.
On a standard drum, the radius stays the same as the cable winds on. On special drums it changes.
DASMA defines a high moment arm as the drum radius at the point of cable peel-off, and a low moment arm as the smallest radius 1, and describes rate of rise as the change per revolution of a drum’s moment arm 1.
Changing the radius changes the pull through the door’s travel, which is how special drums match spring force to the load.
Pounds pull = Torque ÷ Moment arm
Torque- From the springs, in inch-pounds 1
Moment arm- Drum radius where the cable peels off 1
Pounds pull- Force lifting each bottom corner 1
DASMA TDS-160 definitions. A concept, not a sizing method.
Source: [1]
Types of cable drums
| Drum | Shape | Used for |
|---|---|---|
| Standard drum | Constant radius spiral groove | Standard-lift doors (commonly 4 in on homes) 7 |
| High-lift drum | Contoured profile 1 | Doors that rise up the wall before turning |
| Vertical-lift drum | Changing-radius grooves 1 | Doors that go straight up |
| Ball bearing drum | Drum with a ball bearing 1 | Heavier doors |
| Proprietary drums | Matched to a brand’s system | e.g. enclosed or EZ-SET systems 7 |
Example: drum size and spring turns
DDM Garage Doors explains how drum size relates to spring winding. On residential doors with standard 4-inch drums, springs typically gain about 8 coils of length from winding on a 7-foot door and 9 on an 8-foot door. For other drums, turns ≈ door height ÷ drum circumference + 1 7.
| Door | Drum circumference | Turns (DDM method) |
|---|---|---|
| 14 ft (168 in) commercial | 17 in | 168 ÷ 17 + 1 ≈ 10.9 turns |
| 7 ft residential, 4-in drum | About 12.6 in | About 7.7 turns (≈ 8 coils with stretch) |
This is how technicians reason about springs; it is not an owner procedure. It shows why changing drums means changing springs and turns.
Where the drums are
Stand inside with the door closed and look at the ends of the bar above the door. The round, grooved pieces at each end, with cables coming off them and running down beside the tracks, are the drums. They sit just inside the end bearing plates that hold the shaft 1.
From the floor you can see whether the cable is neatly wound in the grooves. Do not touch the drums or their set screws; they are under spring tension 2.
How the cable stays on the drum
The cable stays in the groove because it is under tension. On a standard-lift door, the door’s weight keeps it taut.
Anything that lets the cable go slack, such as a door that binds partway, a broken spring, or a door pushed up by hand faster than the springs take up the cable, can let it jump the groove.
DASMA is especially concerned about wall-mount openers on standard-lift track, because they turn the shaft directly and cable tension is lowest when the door is open. Without the door maker’s provisions, cables can go slack and disengage from the drums 6.
Left and right drums
Drums come in left and right versions, because the cable must wind in opposite directions on each end of the shaft for both sides to lift together.
A left drum on the right end would pay out cable as the door rises instead of winding it in.
Replacement drums are therefore ordered as a matched set for a given door, and a technician checks the side marking before fitting them.
Matched also means the same size and profile. A standard drum on one end and a high-lift drum on the other would lift the corners at different rates and twist the door in its track.
Drums on enclosed and proprietary systems
Some spring systems use their own drums. DDM Garage Doors describes Wayne Dalton’s TorqueMaster, where the springs sit inside the shaft and the cable drums, formed of plastic, support the ends of the shaft; it notes several grooves sit higher than the rest 7.
Clopay’s EZ-SET system places the drum next to a winder at the shaft end 7.
These drums are not interchangeable with standard steel drums. If your door uses one of these systems, replacement parts come from that system, and the technician should know it.
Drums in lift conversions
Changing how a door travels nearly always changes the drums. A high-lift conversion, which raises the door up the wall before it turns back, needs high-lift drums contoured for the longer vertical travel 1, plus longer cables, different springs and new track. A vertical-lift conversion needs vertical-lift drums with changing-radius grooves 1.
Because springs, drums and cables work as a set, a conversion should be quoted as a package from one source, with the maker’s chart behind it. Swapping only the track and leaving standard drums produces a door that will not balance.
Reading drum wear from the floor
Healthy drums show the cable lying in neat, side-by-side wraps. Warning signs are cable wraps crossing over each other, a cable sitting on top of the groove ridges, a gap where one side has fewer wraps than the other, or rust and chips on the groove edges.
Any of these means uneven tension or damage, and a technician should look before the cable frays. Take a photo of each drum from the floor; it helps the technician bring the right parts.
Good drums vs worn drums
Good drums
- Cable winds neatly in each groove.
- Door rises level.
- Set screws tight; no wobble.
Worn or damaged drums
- Chipped grooves fray cables.
- Cracked drums can fail under load.
- Loose set screws let the drum slip on the shaft.
What drums cannot fix
Drums convert torque; they do not create it. A heavy door with weak springs stays heavy whatever the drum. And drums cannot keep a slack cable on; tension does that.
What drives drum repair cost
No prices here; see the cost guide.
- Replacing both drums so they match.
- Cables often replaced at the same time.
- Lift conversions (high-lift) change drums, springs and track.
- Bearings on the shaft if worn.
How a technician replaces drums
Requires releasing spring tension safely first.
- Secures the door and unwinds the springs with proper bars.
- Removes cables and loosens set screws.
- Fits matched drums for the door’s lift type 1.
- Re-anchors cables and sets equal tension both sides.
- Re-winds springs per the maker and checks balance 5 2.
Owner checks
- Look from the floor: cables wound neatly in the grooves on both sides.
- Listen for clicking or grinding at the ends of the shaft.
- Watch for the door rising crooked.
- Book yearly service; never adjust drums yourself.
Danger signs
A cable off the drum, cable wound unevenly or overlapping, a drum that wobbles, cracks in the drum, or the door hanging crooked. Stop using the door and call a technician 3.
Do not touch drum set screws
Drums are held to the shaft against full spring torque. Loosening a set screw can let the drum spin violently. DASMA says repairs and adjustments belong to a trained technician 2.
Standards
Drums are part of the counterbalance system covered by the voluntary ANSI/DASMA 103 standard, which addresses tensioned components 8. On wind-rated doors, replacement parts must be identical to the certified assembly 4.
Drum vs related parts
| Part | Job |
|---|---|
| Cable drum | Winds the lift cable |
| Lift cable | Carries force to the door |
| Torsion shaft | Turns the drums 1 |
| Spring torque | Twist the drums convert to pull |
| Track lift type | Decides which drum is needed |
Myths about drums
- Myth All drums are the same.
- Reality Standard, high-lift and vertical-lift drums differ 1.
- Myth A cable off the drum can be put back by hand.
- Reality It is under tension; call a technician.
- Myth Drums never wear out.
- Reality Grooves chip and drums crack.
Climate and wind
Salt air corrodes drums and cables. Wind-rated doors use specific hardware listed on the maker’s drawing; substitutes can void the rating 4.
What to do
If a cable is off a drum or the door is crooked, stop and call. If you are planning a high-lift conversion, expect new drums, springs and track together. See high-lift track and repair.
Ask for matched drums
Drums should be replaced in pairs and matched to your door’s lift type and springs.
Questions about Cable Drum
What is a garage door cable drum?
A grooved wheel at each end of the torsion shaft that winds the lift cable as the door opens, as DASMA defines it.
What size are garage door drums?
Many residential standard-lift doors use 4-inch drums, according to DDM Garage Doors. High-lift and vertical-lift doors use special drums.
What is a high-lift drum?
A cable drum with a contoured profile that balances a high-lift door, the kind that rises up the wall before turning back. The definition comes from DASMA.
What is a vertical-lift drum?
A drum with changing-radius grooves that offsets spring tension on doors that open straight up, per DASMA.
Why did my cable come off the drum?
Usually because the cable went slack, from a binding door, a broken spring or a wall-mount opener without tension provisions. Call a technician.
Can I replace a garage door drum myself?
No. Drums hold spring torque. Releasing and restoring tension is technician-only work.
Should drums be replaced in pairs?
Yes, so both sides match and the door rises level.
Do drums affect spring size?
Yes. Pull equals torque divided by the drum’s radius, so springs are sized for a specific drum.
What is a ball bearing drum?
A drum with a ball bearing for smoother operation of heavier doors, per DASMA.
Are there left and right drums?
Yes. The cable must wind in opposite directions on each end of the shaft, so drums are made in left and right versions and replaced as a matched set.
Do enclosed spring systems use the same drums?
No. Systems such as Wayne Dalton’s TorqueMaster use their own drums, which DDM Garage Doors describes as plastic drums that support the shaft ends. Parts must come from that system.
Why is my garage door lifting unevenly?
A cable slipping on one drum, a damaged drum or a spring problem can cause it. Stop using the door and have it inspected.
Sources
- DASMA Technical Data Sheet #160, Sectional Garage Door Terminology, retrieved .
- DASMA Technical Data Sheet #167, Residential Sectional Garage Door and Electric Operator Checklist for Home Inspectors and Consumers, retrieved .
- DASMA Technical Data Sheet #174, Building Occupant: Checking a Residential Sectional Garage Door for Damage, retrieved .
- DASMA Technical Data Sheet #183, Garage Door Component Substitution, retrieved .
- DASMA Technical Data Sheet #190, Factors Affecting Spring Cycle Life, retrieved .
- DASMA Technical Data Sheet #1501, Standard Lift Garage Doors with Jackshaft Operation, retrieved .
- DDM Garage Doors (parts supplier), Garage Door Springs: types, measuring and FAQs, retrieved .
- DASMA, The New DASMA 103 (interview on the counterbalance standard, Door & Access Systems, Winter 1999), retrieved .
Expert review
Written by the HyreGarage Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Definitions from DASMA TDS-160; tension warning from TDS-1501; safety from TDS-167 and 174; drum size and winding relationship from DDM Garage Doors; standard from DASMA’s DASMA 103 article.
Suggest a correction. We fix errors and say what changed.