Q:

Is it common for the left side spokes of a front disc wheel to have more tension than the right side spokes?

Wiping my bike down after a wet ride, I noticed that the left side spokes on my front wheel are tighter than the right side.  I don't have a tensionometer but squeezing pairs on each side and plucking spokes around the wheel yields a feeling of increased tension and a tad higher pitch sound of the left side spokes. This is generally so around the entire wheel. 
The wheel is a 26 inch Mavic 119. The 32 spokes are laced 3 cross.  The 9mm QR axle is fully engaged in the suspension fork's dropouts, and each side of the rim is equidistant to the inside of the fork leg. With the tire still on, can see it seems to run true and centered. The disc rotor is 160 mm Shimano. 
Do disc-brake wheels have greater spoke tension on the left, rotor side?

A:

The side with the disc is dished in more than the other (that is, the spoke flange is closer to the hub's centerline), so yes, I would expect it to have higher tension.

