Yes I admit it first hand. I'm a nimkumpoop. Bought a pair of used rims. It had some sticker residue. Didn't think much and sprayed WD40 to remove the residue. MISTAKE #1
Installed them on the bike and went for a ride. MISTAKE #2. Rear brakes lost all stopping power. Thankfully the front was disc brake. Otherwise I'd be careening right onto a tree or worse.
I have since applied degreaser on the rims & pads. The result was better, but still not good enough. Any ideas to try?