Truck pulls right when braking

[dstuart]

I’m stumped on this one and need some help! I’ve got a 67 F100 and recently rebuilt the entire drum brake system top to bottom. New master cylinder, brake hoses, steel lines, new slave cylinders, new shoes, and new hardware/springs. Silicone brake fluid. New front bearings, too. The only original part is the differential valve which I cleaned thoroughly before reinstalling. Bled the system, adjusted the shoes, and everything seemed to be working fine for the first 50 miles or so. Now when I brake firmly, the truck pulls hard right and the steering wheel pulls hard to the right as well. This will tell you how bad it is: If I mash the brakes hard at 25 mph and let go of the wheel, by the time the truck stops, the front wheels are turned about 45 degrees to the right. The rear wheels are working well enough to skid the rear tires. I suspected the left front brake wasn’t working as well as the right, so I removed the drum and had my son pump the brake pedal. The shoes are moving— the front shoe activates first, followed by the rear shoe. I’ve looked through the troubleshooting guide and can’t seem to identify a likely source of the trouble. Any advice will be greatly appreciated!

[ddcrim]

Put a hose on the left bleeder (tight) and the other end in a clear bottle with brake fluid at a measured height.
Have son pump and hold pedal then open bleeder. Do this 3 times. Measure fluid in bottle.
Repeat on right side. With all things the same (pedal pressure, the way you open and close the bleeder) the
fluid pumped into the bottle should be the same. This rules out any clogs in the lines. Don't let the MC run low
during this test. The pressure needed to press on the pedal when the bleeder opens also tells you if you have
a line problem.

[jzjames]

I would start to suspect the new springs/brake shoe retainers or something broken or not installed right
inside the right brake drum -if its not the wheel cylinder itself binding up,
Forward brake shoe smaller rearward shoe larger?

[67 short box]

mine did that too. same truck. the new drums I bought are normal china junk. the right one is not true. I took off the right front and turned it by hand. it would turn free then get tight all within one revolution. you may want to check that at some point. probably have it turned and true it back up. I put the old ones back on and no more pulling to the right.

[Johnnewc]

I had the same problem on my dads 69 f100. I thought I didn't adjust the brakes right. I always tighten them until I can't turn the wheel. I will then back off the adjuster wheel the same amount on each side just until the brakes drag just a little. After adjusting the brakes I checked the cable on the brake hardware that adjusts the brakes automatically when you reverse and hit the brakes. The cable was too long because it was worn out. So I replaced every thing and all was well. There is a little plate that will push on that adjuster wheel. That contact point needs to be fairly firm or else your brakes won't adjust. That was my experience with this issue.