Reference
Garage Door Parts Glossary
Every part a technician might name on your invoice, explained in plain English — with typical 2026 Denver replacement costs so you can sanity-check any quote.
Torsion spring
$225–$385 replaced- The wound steel spring mounted on a shaft above the door opening. It counterbalances the door's weight so the opener only has to move it, not lift it. Rated in cycles — a standard 10,000-cycle spring lasts about 7 years at four openings a day.
Extension spring
$185–$310 replaced- Springs mounted along the horizontal tracks on either side, stretching as the door closes. Common on older Denver homes and lighter doors. Must have safety containment cables.
Lift cable
$145–$265 replaced- Braided steel cable running from the bottom bracket to the cable drum. It transfers the spring's torque to the door. Frayed cable is a common failure after a spring breaks.
Cable drum
- The grooved aluminum spool at each end of the torsion shaft that winds the lift cable. Mis-set drums make one side of the door hang low.
Bottom bracket
- The bracket at the bottom corners where the cable attaches. It stays under full spring tension even when the door is open — never unbolt it yourself.
Roller
$85–$140 per set- The wheel that runs in the track. Steel rollers are loud and wear fast; 13-ball nylon rollers are quiet and last far longer in dry Colorado air.
Track
- The vertical and horizontal steel channel guiding the rollers. Bent or spread track causes binding and doors coming off track.
End bearing plate
- The plate at each end of the torsion shaft holding a bearing. A dry bearing is the source of most rhythmic squealing.
Center bearing bracket
- The middle support for the torsion shaft, mounted above the door center.
Photo-eye safety sensor
- The paired infrared sensors 6 inches off the floor. If the beam breaks or the eyes are misaligned, the door reverses — the single most common reason a door won't stay closed.
Auto-reverse (2x4 test)
- The federally required safety function that reverses the door on contact. Tested by laying a 2x4 flat under the door and closing it; the door must reverse on contact.
Travel limit
- The opener setting that defines fully open and fully closed positions. Wrong limits make the door stop short or slam and bounce.
Force setting
- How much resistance the opener applies before it stops or reverses. Over-forcing masks a mechanical problem and burns out the motor.
Belt drive vs chain drive
$395–$795 installed- Belt drives use a reinforced rubber belt — quiet, ideal for a bedroom above the garage. Chain drives are cheaper and louder, fine for detached garages.
Battery backup
- An opener battery that runs the door during a power outage. Valuable on the Front Range where wind and snow outages are routine.
Astragal (bottom seal)
$65–$145 replaced- The rubber seal in the bottom retainer. Cracked seals let snowmelt, dust and rodents in.
Stop molding / weatherstrip
- The perimeter seal on the door jamb. Critical for keeping an attached Denver garage above freezing.
R-value
- Insulation rating of the door. Polystyrene doors reach roughly R-6 to R-9; polyurethane (e.g. Clopay Intellicore) reaches up to R-18.4 — a meaningful difference in an attached Colorado garage.
Panel / section
$285–$650 per panel- One horizontal segment of the door. Individual panels can often be replaced instead of the full door.
Strut
- A horizontal reinforcing bar across a panel. Required on wide doors and on the top panel when adding an opener.
Cycle
- One full open-and-close. Spring life is measured in cycles, not years — a family with two drivers can burn through a 10,000-cycle spring in five years.
Door balance
- A properly balanced door stays put when lifted halfway by hand with the opener disconnected. Loss of balance is the earliest sign of spring fatigue.
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