Long-arm vs short-arm v-brake linear-pull brake: understanding the sizing When a manufacturer's linear-pull brake comes in two versions, a "short-arm" (82mm) and a "long-arm" (108mm) where/how is that measurement taken? 

Is it merely the length of the brake from the tip to base?

Or is the measurement taken on-center from the top-bolt (up near to the noodle) to the bottom bolt (holding the brake to the frame)?
I just measured some Tektro brakes that I have. The measurements coincide with a center to center distance. I measured from the center of the brake arm mounting hole to the center of the cable clamp bolt. One consideration is tire size. Larger tires may hit the brake cable on the short arm models.