Left side, so that there's weight over the kickstand.

Putting it on the RIGHT puts the weight over the kickstand. Putting it on the left puts it past the kickstand and makes it tippy.

I'm in the "meh" camp. I like to keep panniers as far back as possible, and with the rack I use that means asymmetrical positions for mounting hooks. Plus, at least with my old Ortliebs the lower hook is always asymmetrical. So each of my rear Ortliebs only fits one side of the bike well. If I leave home with just one pannier, I grab one without checking. When I get to the bike, I see which pannier I took and just throw it on the rack.

Speaking of Panniers, I like this one http://ecx.images-amazon.com/images/...L._SL1500_.jpg

Much cheaper than the Topeak version.

' not sure if it'll work with most rear racks, though.

Mine always went on the left, so that in the dark I could run an extra taillight over there and give the impression that I'm farther to the left than I am. I never felt it made a difference in the daylight.

Left, for many of the reasons mentioned above.

Interesting. I've never seen this before. Thanks for sharing.

When I carry one pannier, I tend to carry it on the left side, on roads that have a fair amount of camber I find it easier to have it on the high side (assumes right hand drive countries), rather than dragging downhill.

If I'm carrying that much stuff I'd rather have it closer to the center of the wheel, even if it is only on one side, but I use traditional racks. I can see those that use only a beam rack liking it though.

Regular commuting bike: left, since it doesn't have a kickstand and I dismount left --> lean it on its right

Hauling bike: right, since it has a kickstand and it's more stable that way

I can't imagine it makes a difference with passing cars.

the ortlieb downtown is made to go on the left. On my dirt road bike, the first pannier I found was the right one. So my bikes with single panniers don't have them on the same side

Right side. My rack is just a hair too small, so occasionally I have a heel strike event. When that happens I want the pannier to fall towards the curb and not into traffic. Yeah, a new rack would be a good answer, but so would having the money to afford it.

Right side. The bush I leaned my bike against on by me door was on the other side.

Sometimes the left when I came home, depending on which way I was leaning on the bike rack.

OOps.. ' did not know it only works with seatpost racks. Scratch that one.

Left side.

- I lean my bike on its right side so a left side pannier is easier to load. This is the main reason.

- Reflective material is on traffic side. Hopefully it makes the left side look bigger so drivers give more room.-

- Pannier won't touch the curb.

Someone makes little adpaters that set the rack back a little, those shouldn't cost very much.

Not sure why but I switch sides every week or so. But I always use the same side going home as I used coming in. /shrug