Have replaced v-brakes and they still squeak. What to do?
Is there a chance the rim is wearing out? Have you tried a different wheel? Have you tried toeing the brakes in the opposite direction? It sounds like you've tried just about everything else. I'm leaning towards the wheel being the issue. Otherwise it sounds like the frame is just prone to resonance with the vibration of the brakes. I've got a mtb frame that doest this horribly with the back brake. Several friends have the same frame with different brakes but the same issue. Some frames are just more likely to resonate than others, though it's usually more of a wheel issue with rim brakes.