Reddit mentions of Tektro Alloy Brake Cable Triangle w/cable Black

I have the same brakes on my ‘85 Miyata. Good advice so far. I usually loosen the bolt on the back of the brake just enough so that you can move the pads and toe-in (using that thick tapered washer with the nub on it) to the correct position but not so that it’s loose and will move on its own.
Ratcheting closed-end wrenches are helpful and you can also use the correct sized Allen key on the other side to hold the post in place with your other hand while you tighten the bolt in the back. It usually takes me a few attempts to get just right on each side. I recommend getting cartridge pad holders (I use the kool stop “cross” ones) and replacing the straddle wire/yoke with the newer Tektro which is a cheap way to greatly improve these brakes. Once they are set up optimally (straddle cables should make a ~90deg angle with the post and attachment point) they actually work quite well.