Track Radius: Why 12-Inch and 15-Inch Track Are Not Interchangeable

Track radius is one of those specifications that never comes up until something has been mixed and matched, and then it explains a binding door that nobody can diagnose.

What radius means

It is the curve where the vertical track turns into the horizontal track above the door. Residential systems commonly use a 12-inch or 15-inch radius, and the choice is driven by available headroom: a tighter radius needs less clearance above the opening.

Why it has to match everything else

The radius determines the arc the rollers travel through as the door transitions from vertical to horizontal, and that arc has to suit:

• The section height. A door with taller sections needs a wider radius to make the turn without the section corners binding.
• The hinge numbering. Hinges on a sectional door are numbered by position, and the offset built into each one is calculated around a particular radius and section height. Fitting the wrong number in the wrong position is a common cause of binding that people chase around the track for weeks.
• The roller stem length.
• The headroom available.

What mismatched radius looks like

• The door binds or slows at the same point in travel every cycle — right at the transition.
• Rollers wear unevenly or pop out of the track at the curve.
• The top section flexes visibly as it goes through the turn.
• Hinges show wear or cracking at their pivot points.
• The opener strains at a specific point rather than throughout.

Where it goes wrong

Almost always in a partial repair. A section gets replaced with one of a different height, a set of hinges gets replaced with the wrong numbers, or a length of track gets swapped from another door. Each individually looks like a like-for-like part and none of them is.

What we do

On any track or section repair we check the radius, section height and hinge numbering as a system rather than replacing the visible part in isolation. It is the difference between a repair that lasts and one that comes back. Call (423) 262-3147.