Originally Posted by
mcours2006
If you have a long commute, like over an hour, that backpack against your back is going to be one sticky mess of sweat on you backside. On my 50-60 minute commute I begin to feel the sweat on my back at about the 30 minute mark if I'm wearing a backpack, but without the backpack I can make it all the way without much sweat on the back. That the difference.
I do have a bike with rack and panniers, but I find it to be too much of an aerodynamic drag. I'll only use it when I have loads to carry, and even then I'll still wear my backpack.
I don't know how long the OP's commute is. Mine is under 3 miles each way, and takes about 15 minutes each way. I don't assume most bike commuters are riding 50-60 minutes each way, but I could be wrong. I tend to drop off stuff i need at the office (a few days office attire, lunch and breakfast items for my office fridge and desk "pantry.") That way I can ride with very few items in my pack, but it's where I put my wallet, keys, office lanyard, phone, tire pump, bike multi-tool...