While rebuilding the brakes on my one ton, I welded up those grooves and got the backing plate area for the shoes smooth. My grooves were almost holes through the plate and I could see how yours might be hanging up on them, especially if you’ve reused the old shoe springs. A new set of those make a HUGE difference in pulling power. Ask me how I know...😉 I had to replace mine after 500 miles when one broke and made an awful grinding sound in the front drum.
It can’t hurt to weld those grooves up and see what happens. That’s a freebie. Time, yes. Cost, no.
