Originally Posted by
RI_Swamp_Yankee
I can't stand wearing a messenger bag or backpack on a bike. For those of you who claim it doesn't move around on you or toss you off balance, god bless you, because you're way more talented and/or lucky than I've ever been. The pannier's been a godsend, and the reason why I still commute year 'round.
My first time riding with a messenger bag was almost my last. I returned it and got one with a cross strap. That took care of 90% of the shifting. The rest is making sure it's worn high and that it's packed right. Putting something flat and stiff at the back of the bag can cause problems. The way the straps are designed matters too.
It's been awhile since I've done much riding with a backpack but as I recall once I got a pack with both a sternum and a waist strap, any shifting problems were taken care of.