wrote:

I've heard people say use the shortest extension bar you
can get your hands on. I don't understand why. It should be the same torque
if I used a 16-inch extension bar, right?


no because some force will just be twisting the bar, Imagine a bar a
mile long, you twist one end with a known force, the other end would not
move.

That makes too much sense for Usenet!

I guess there are two faults with a 20" extension bar that a 2" extenstion
bar wouldh't have then.

1. Some of the measured torque is wasted in twisting the bar, and,
2. Any extension bar not at 90 degrees to the nut also changes the torque.

Both effects are probably slight - but perhaps measurable?