Current Projects chat and miscellany

I was an ass and didn't clean my road bike after taking it out in January when it got a bit grimy and now I'm back training properly I find that the rear brake calliper doesn't quite spring all the way open. I've cleaned it now and everything runs smoothly but still the calliper only springs back to about 80% open, it's only when I manually spear the arms of the break that it opens fully.

I don't think it's the cabling because everything else seems smooth. There is some small rust on the return spring, might this be the problem? I'm unconvinced. Is the most likely scenario that there is still dirt somewhere in the mechanism and I need to remove, dismantle and clean the whole calliper thoroughly? If so is this reasonably easy, I've not taken a brake apart before.

Brakes are SRAM Rival.

They're simple dual pivots. It's unlikely you'll need to dismantle them.

There is likely a little corrosion/dirt in the center pivot (this one is the most exposed to road grime). Take it off the bike, take the pads off it, and shoot it with some wd-40 or gt-85 while actuating it manually to work it in. Then maybe even apply a drop of lube to each pivot, wipe off the excess thoroughly and re-install. It should be fine, and I doubt the corrosion on the spring is the problem.