Is the distance between the roof and the supporting beams standardized?

HI,

"On the Golf 3 Variant, the original..." The crossbars of the VW roof rack are adjustable, allowing me to freely choose their position on the roof rails, which taper slightly towards the rear.

The 3C supports are rigid, so they define their position on the railing.

The Opel Zafira also only has 3 fixed positions where roof racks can be attached.

The Zafira has a distance of 70 or 115 cm between the front center and the middle, or between the front and rear.

I haven't been able to measure anything yet with the 3C.


Are the distances between the beams standardized in any way?
Because how else could a Kamei roof box possibly fit on different vehicles?

m;

Okay, here's the translation:

"Edit: This refers to the fixed distance 'd'."

I could imagine that the distance is standardized, as the distance is also specified for sedans (e.g., Golf IV: In that model, the roof racks can only be attached at specific points).

Furthermore, a fixed position could offer the advantage of achieving a more optimal weight distribution for the vehicle.

"The roof boxes have several holes in them, perhaps there are several standard sizes?"

Okay,

The original VW roof racks have a distance of 76.0 cm and look like this: