[Flathead Fever]

some older copper brake washers had raised concentric circles that helped make the seal. The modern ones you get now are just flat copper washers which might or might not seal. It depends on if the part on either side of the washers have the concentric circles or are smooth. I had problems at work using smooth washers with smooth parts. Trying to use the smooth flat copper washers that came with the new calipers. A few times I had to remove the new washers and put the old ones with the concentric circles back in to stop the leaks.