Originally Posted by
sauerwald
Ask him if he has taken into account the fact that the pavement is not level, but roads are designed with a crown in the middle so that rain runs to the gutters. As a result of that, a bicycle with no panniers, going straight on a level road could expect to see a greater load on the left hand side of the tire. To even this out, you would want to add a loaded pannier to the right hand side of the bike.
No, you'd want to place the pannier on the left side of the bike. That way the bike will be leaned slightly to the right to maintain proper balance (center of mass over the wheels) and would then be closer to perpendicular to the road surface if that's crowned in the center.
Somewhat paradoxically, adding weight to the right side of the bike will result in added wear on the left side of the tire.