Commuting - Keeping bags strapped down

The bumps in the road on my commute have been enough to jar my rear rack bag to fall off a couple times now. The bag I purchased just doesn't exactly fit the rack when using the velcro straps (they turn out too short). I'm temporarily using a tire liner that I wrap around a couple times, but I'm wondering if you guys have a more elegant solution. Thanks!

Old tubes, bungee cords.

several places sell cargo nets (stretchable with bungee hooks on the perimeter). REI, your LBS, probably your LMS.

I use a couple of 2ft Velcro straps I picked up at and electronics store. I have also seen them at Home depot.

See, this is the problem with living in the big city. A good ol' boy wouldn't ask that question before having tried all possible combinations of duct tape, super glue, and bungee cords.

I may be overdoing it on my backpack-on-the-rear-rack. I have:
- Two carabiners locking the top carrying strap to the front of the rack Just In Case
- Two bungee cords, perpindicular to one another
- A cargo net

See, this is the problem with living in the big city. A good ol' boy wouldn't ask that question before having tried all possible combinations of duct tape, super glue, and bungee cords. Well, I'm not a "good ol' boy" but I did live briefly in a place called Ellijay, GA. Does that give me some street (rural route) cred? :D

A cargo net sounds like a great idea--didn't know they made 'em for bike racks.

If Bungee cords don't do it, pick up some very long velcro strips at any hardware store.
(They're also great for rolling up clothing.)

After problems with my elasti-strap du jour, I finally picked up a set of two of these for about $7 at WalMart. Not as effective or aesthetically pleasing as baling wire or duct tape, but it works in a pinch.

A cargo net sounds like a great idea--didn't know they made 'em for bike racks.

Sounds like you might be guilty of the same issue as I. And I mean this sincerely. I often look for bike-specific solutions for problems instead of looking around for other (often cheaper) solutions to the problem.

several places sell cargo nets (stretchable with bungee hooks on the perimeter). REI, your LBS, probably your LMS.

+1 on the cargo nets. I actually got a similar product for motorcycles. They amount to a net made of bungees. Just cover your bag and strap it down, it won't come off. And you don't have to hook it nearly as tight as you do bungees, it's fantastic, and easy to use. You can even slip something extra under it when you need to, like a jacket when you get hot.

Mine set me back $5. Best $5 I have spent in a long time.

I picked up one of the above cargo nets in Wal-Mart's automotive section. Bag hardly moves.