I'm trying to put some life back into a set of rear brake avid SD 7 calipers that have become very gritty. I noticed that the rear calipers didn't want to spring back after you hit the lever. I took them off the bike and realized that the spring didn't want to move freely. I cleaned them off with some rubbing alcohol, squirted a bit of light weight "turbine oil" I have kicking around in them, and worked them for a bit and used a shop towel to wipe away the bit of grit that came out of them. They're smoother than they were, but it seems like the best solution would be to take them apart and clean the bushing out, as there's still a tiny bit of grit in there. Is there any way to clean the bushings out, or do you just oil them and hope for the best once they get gritty? (I could replace them, but they're only a year old, and I want to reuse them if possible.)
I had the exact same problem after a full winter of commuting with these brakes. Avid makes a pretty inexpensive overhaul kit, which was the only way i could bring them back to life. The spring also broke, and the kit comes with the springs, so it saved a lot of hunting around. Make sure you get the right kit for your 7s.
This year I rode with some old school Cantis, and had no problems at all.
Ok, I've got Avid calipers on my bike which locked/gunked up on me at one point this winter. Nowadays they work just like new. Here's what I did:
Unhook the quick release, squirt WD-40 or some other kind of penetrating lubricant all over the joints while actuating the break by hand. Squeezing the break lever just isn't going to cut it. You've got to swing them back and forth as far as they'll go. Do this A LOT (like, for 5-10 minutes) until they run butter smooth again. Wipe off excess lubricant and let dry. Follow up with a drop or two of chain oil (or the like). Voila.