Bearing Bar And Cross Bar Explained

Reading The Notation

A section written 30x2.5 is a bearing bar 30 mm deep and 2.5 mm thick. A cross bar written 8x2 is 8 mm by 2 mm flat; one written with a diameter symbol is round bar. Depth is always the first figure and it is the one doing the structural work.

Depth Carries Load, Thickness Resists Damage

Doubling the depth of a bearing bar does far more for load capacity than doubling its thickness. Thickness matters for local deformation, for corrosion allowance and for how the bar behaves where a wheel lands between supports.

Pitch Is The Number Nobody Sends

Bar pitch, the spacing between bearing bars, changes both the load capacity and the clear opening. It is also what makes a replacement panel match the run beside it. Send it with the section.

Flat Cross Bar Or Round

A flat cross bar squares the panel up more rigidly. A round cross bar is lighter for the same bearing bar and leaves a more open mesh that sheds grit. Both are produced here; the choice follows the environment.

When The Cross Bar Is Structural

In heavy covers the cross bar stops being a spacer. A 30x5 flat cross bar in a 100x5 panel is distributing wheel load between bearing bars, which is why heavy covers are not simply light covers with thicker bars.