Cables are the part of the garage door system everyone forgets about. They sit quietly in the corner of the garage, carrying the door's full weight every time it moves. They don't make noise. They don't need lubrication. They don't have a battery or a sensor or a chip.

And then one day they snap, and the door comes down on one side.

This post is about catching them first.

What the cables do

Two steel cables run from the bottom corners of the door, up along each side, around the cable drums at the ends of the torsion shaft. They are the mechanical connection between the door's weight and the spring's stored energy. When the spring unwinds, it turns the drums, which wind the cables, which lift the door.

When a cable breaks, the spring's energy can't lift that side of the door. The other side keeps lifting. The door goes diagonal. Sometimes the unbroken cable holds the door at an angle. Sometimes both cables fail in quick succession and the door comes down hard.

Why they fail

Cables are made from 7x19 aircraft cable. That spec means: 7 strands, 19 wires per strand. Galvanized steel. Typical residential diameter: 3/32" or 1/8".

The 7x19 construction is flexible (it can bend around the drum repeatedly without fatiguing) but the small individual wires inside each strand mean that wear-from-bending-friction wears each wire faster than a thicker single-strand cable would.

Three things kill cables:

1. Bending fatigue. Every door cycle, the cable bends 90+ degrees around the cable drum. Tens of thousands of bends, and the individual wires inside the strands start breaking. You can see this — the broken wires push out of the strand like splinters.

2. Corrosion. Salt air, humidity. Same Richmond story as everything else. The galvanizing wears off the surface, the underlying steel rusts, the rust eats into the strands. Worst at the bottom-bracket end of the cable where standing water can pool.

3. Misalignment. If the door isn't level — track is bent, header is sagging, bottom brackets are misaligned — the cable wraps the drum at an angle. It wears unevenly, fails on the heavily-loaded side.

A properly-installed cable on a balanced door in a dry climate can last 25 years. A cable on an unbalanced door in a Steveston garage can fail in 6.

The inspection

This is part of the two-second test (post 1), but I want to call it out separately because cable inspection is easy and the failure consequences are bigger than people realize.

With the door fully closed and the opener disconnected:

  1. Stand inside the garage. Look at the bottom corner of the door on the left side. Find where the cable attaches to the bottom bracket.
  2. Run your eye up the cable, slowly, from bottom to top. You're looking for: - Frayed strands ("splinters" sticking out of the cable) - Rusty patches where the galvanizing has failed - Kinks or bends in the cable that aren't supposed to be there - Cable that's come out of its drum groove at the top
  3. Repeat for the right side.

A healthy cable looks like a smooth shiny grey rope. A failing cable looks fuzzy or scaly. A failed cable is in pieces.

If you're not sure, run a paper towel along the cable (with the door secured, opener disconnected, door fully closed — never near a wound spring or a cable under load). If the paper towel snags or catches, the cable is fraying.

Why cables and springs fail together

About 25% of my "broken spring" calls reveal a frayed cable that probably would have failed within months. About 15% of my "broken cable" calls reveal a spring at end-of-life.

This is because they age together. The spring that breaks because it's been doing too many cycles in too-corrosive conditions has been pulling on the same cable for those same cycles in those same conditions. Both components are on the same wear curve.

My standard recommendation when one fails: inspect the other carefully. If there's any doubt, replace both. The labour for replacing cables-while-doing-springs adds maybe 15 minutes to a 45-minute job. Replacing cables as a separate service call later is a full $215–$345 charge.

How replacement works

Cable replacement requires the door's spring tension to be removed first (you can't unwind the cable from the drum while it's loaded). This means either:

For the first case (already-failed spring): cable replacement is straightforward. Unwind the broken-spring side, replace cable, rewind. About 30 minutes per cable.

For the second case (preventative replacement of intact cables on intact springs): the job becomes a full spring-and-cable service. You're doing the dangerous spring work anyway. Most shops will do this as a combined job for less than the sum of two separate calls.

The spec question

You want 7x19 galvanized aircraft cable for residential. Do not accept 7x7 (less flexible, fatigues faster around the drum), and do not accept anything not specifically rated for garage door use. The cable has to handle hundreds of cycles per year and full door weight every cycle.

The diameter matters too. Standard residential is 3/32" or 1/8" depending on door weight. A 16x7 double door over 65 kg typically uses 1/8" cable.

Premium cable upgrades exist (stainless steel 7x19, mostly for waterfront commercial use). For residential in Richmond, standard galvanized is fine if you replace it on schedule.

The DIY question

I'll be brief: don't.

Spring tension has to be released first. That puts you in the same dangerous job as spring replacement (post 9). And the actual cable work itself requires routing the cable correctly through the bottom-bracket and the drum groove — get it wrong and the cable will derail and fail on the first cycle.

This is the one job where I genuinely think DIY is a worse decision than spring replacement. With springs, careful methodical work can succeed. With cables, the integration with the spring system means you're taking on all the spring risk plus the cable risk for less money saved.

When to replace preventatively

Three triggers:

  1. Visual signs of fraying or corrosion. Anywhere on either cable.
  2. You're already paying for spring replacement. Add cables if they're over 8 years old.
  3. You can't remember when the cables were last replaced. If "never" is the honest answer and the door is 12+ years old, replace them now.

Cost reality check (2026, Lower Mainland CAD) - Cable pair replacement (cables only, on broken-spring door, scheduled): $215–$345 - Cable pair replacement (preventative, on intact springs — includes spring tension release/rewind): $385–$525 - Cable pair + spring pair (combined service, most cost-effective): $525–$795 - After-hours cable repair (one cable snapped, door stuck): $485–$725 - 1/8" 7x19 galvanized cable wholesale: $8–$14 per cable - Stainless steel premium cable upgrade (Steveston / Sea Island only): add $45–$85 per pair

A specific Gilmore story

A horse property owner on Williams Road just east of No. 5 Road in Gilmore called me last winter about a "weird thing" with his garage door. The door was hanging slightly crooked when fully closed. Not a lot — maybe 2 cm lower on the left than the right. He'd noticed it Tuesday and called me Friday.

I drove out and looked. Left-side cable was 90% failed. Three of the seven strands had completely separated. The remaining four strands were holding the door, but two of them were visibly fraying. I gave that cable maybe two more cycles before complete failure.

The door was an older 14x7 double, original to the 1991 build. Springs were 8 years old (he'd had them replaced once). Cables were original — 33 years old.

I replaced both cables and both springs (the springs being 8 years old made the math obvious — get me back out there in 4 years for cables again, or do both now). Total: $785 including the IPPC-90 spring upgrade because his property is exposed to wind off the river.

The cost of doing nothing: the cable would have snapped on the next cycle. The door would have come down diagonal. Best case: a $625 spring-and-cable emergency repair. Worst case: damaged panels (add $885+) or a hood-deep dent in the new horse trailer he'd just bought.

He thanked me for explaining what I was seeing. He also told me his previous garage door contractor had never once looked at the cables in 20 years of annual maintenance visits.

This is the part of the trade I'm trying to change.

That's the post.

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