I have a mountain bike with a rear suspension system on it. The back fork is attached to a spring and a piston so that it can give a bit when I hit a bump. Will one of those rear pannier racks fit on it or would it lock itself onto both the wheel and the frame. If it locked to both the frame and the wheel I suspect the up and down movement of the rear wheel would break it.
Rear Rack For Mountain Bike
If you only need to carry a modest amount of gear a seat post rack like McG recommends will work. This type of rack won't support enough weight to carry much gear, though. Plus, be sure you have a good, metal seat post. It'll toast a fancy carbon post in the first couple of rides. In any case, you are correct. You can't mount a rack that affixes to both the rear dropouts and the seatpost on a full suspension bike. Basically, you can mount a rack on any two points that don't rotate or move independently. Depending on the design of the rear triangle of your bike, you should be able to mount a rack that affixes to the rear dropouts and upper seatstays. Or, if your bike is equipped for rim brakes, you can affix the rack to the rear brake bracket. If there is a pivot at the dropout and seatstay, you should be able to affix the bottom of the rack to the lower seatstay. Personally, I'd recommend taking the bike to your favorite bike shop and get them to help you out. Hope this helps.