Touring - Backpacks?

What do you guys think of using backpacks for an overnight 35 to 40 mile tour? My girlfriend and I are going to bike the Leelanau trail and neither of use have panniers. We're wondering what sort of cons there are to using backpacks to hold a change of clothes, camera, some personal items, snacks and a bit of extra water? The backpacks we have are technical hiking packs from REI (traverse 30 or something) and have straps across the chest and waist for stability as well as some textured material so that it doesn't press flat against your back.

Thanks for your help

I use a similar, though smaller, pack as a pannier. I use carabiners on the side cinch straps and hang it on the non-drive side. You may need to fiddle with the fit a little, but i have had great results with the set up. I don't use panniers anymore.

Backpacks are fine for overnighters. Day packs might be more like it (smaller). Stow your sleeping gear and tent on a back rack to get rid of the bulk. That's how I used to do it before I discovered panniers.

Thank you to both of you. As we already have the backpacks and we'll be using new bikes (we hope to buy them a week before the trip), I think it will be less of a headache to just use them.

Thanks!

You might want to buy the bikes a little earlier and build up to a 35-40 mile ride (or even 17-20, if the 35 to 40 is a round trip figure). The camping will be more enjoyable if you're not in intense pain from riding too far.

She's been biking since Spring, I've been working up to it on my Dad's old ten-speed. I know conditions aren't ideal, but it's the trail isn't too rigorous.

Also, even though it'll be approximately 17 to 20 miles each day, we'll be staying the night in a hotel room with a whirlpool. I definitely lucked out in finding a room that nice during Traverse City's film festival. :-)

Sure, for an overnight hotel trip, just pack as light as you can and go for it! My first tour I carried a change of clothes and snacks in a camelback and my friend carried all the camping stuff. He must have known what he was doing - I got hooked!