Grrrrrrrrrrr!!! Drum Brakes !!!!!

[72stepside]

I think I have wrestled with drum brakes for the last time. I have taken apart, cleaned, made new (cylinders, shoes, springs, master cylinder), adjusted, etc the front drums on my truck. Good pedal. Both sides bleed out with consistent flow. Distribution valve isn't stuck. I haven't changed the steel lines, hoses, or little steel lines from hose to cylinder.

Sometimes the truck stops like a champ. Other times, it pulls really bad to the passenger side. ALWAYS to the passenger side. I won't touch a thing... step on the pedal and it's back to stopping perfectly. WHAT GIVES ????

I've had a disc brake set up from a 77 F100 in my shop for a while and have been avoiding the swap. I think I can't avoid it anymore. I was real good about getting the axles, spindles, springs, hoses, radius arms and all. I forgot the proportioning valve. That may have been a fatal error because the local yards have begun to specialize in crap, not cars or trucks.

So, two questions...

1. What am I forgetting on the front drums?

2. Any idea how much a new proportioning valve costs? Local parts stores don't sell them around here. They all say, "go to the dealer."

[theskytoucher]

The problem with the drums could be the rubber lines running from the frame int the wheel cylinder!!! But i dont know why it wouldnt do it all the time???

[FORDification]

If the rubber lines are bad on the inside, which they often do, they're holding pressure when you take your foot off the brake pedal...sometimes.

I'd venture to say you've either got a bad flexible line or a wheel cylinder that's sticking.

[67F250CS]

I think I have wrestled with drum brakes for the last time. I have taken apart, cleaned, made new (cylinders, shoes, springs, master cylinder), adjusted, etc the front drums on my truck. Good pedal. Both sides bleed out with consistent flow. Distribution valve isn't stuck. I haven't changed the steel lines, hoses, or little steel lines from hose to cylinder.

Sometimes the truck stops like a champ. Other times, it pulls really bad to the passenger side. ALWAYS to the passenger side. I won't touch a thing... step on the pedal and it's back to stopping perfectly. WHAT GIVES ????

I've had a disc brake set up from a 77 F100 in my shop for a while and have been avoiding the swap. I think I can't avoid it anymore. I was real good about getting the axles, spindles, springs, hoses, radius arms and all. I forgot the proportioning valve. That may have been a fatal error because the local yards have begun to specialize in crap, not cars or trucks.

So, two questions...

1. What am I forgetting on the front drums?

2. Any idea how much a new proportioning valve costs? Local parts stores don't sell them around here. They all say, "go to the dealer."

I have one if you strike out. 10 bucks plus shipping. Shipping can range from 3 dollars or it can go priority for a couple more bucks.

[71PA_Highboy]

It can also be the master cylinder...

OBTW... I have the same problem...

In the master cylinder there are residual pressure valves that maintain 2-10PSI in the line to keep the wheel cylinders rfom retracting too much... if it doesn't seal it allows the flid to come back into the master cylinder.

Combined with stronger springs on the drivers side, it can cause the drivers side to engage slower... hence the pull...

I have also found the self adjusters to not be workling too well, and this can cause the problem...

HTH,

Eric

[flyboy2610]

Crap in the distribution block?
(A possible suggestion as to the cause, not a recommendation as to how to fix it! )

[67heavystepside]

I WOULD START BY REPLACING THE TWO RUBBER BRAKE HOSES, AND SEE WHAT THAT DOES.

[MadMaxetc]

Since you have almost new everything else then I would do the Hoses. $20 should be about it.

The disk drake swap is easy if you have it all ready to go. I would pull it (77) appart and clean all the peices up. Then have the king pins done.

If you want to know about prices I have a PDF off all the money I spent on my convertion on my Web Site.

[Jake11]

Hot spots

[xxxtina63]

Check the star wheel on the adjustment. Some are automatic and some aren't. When it pulls to one side with new hardware, that's usually it. That or drums. Spin the tire by hand. Adjust the wheel until you detect drag when spinning the tire. I usually back off the star wheel adjustment a little then, so you have zero drag. You may have to rebleed the lines, depending on how off the adjustment is. That's how I've always done mine and have never had any problems, even with crappy drums.

[Zeke71250]

I'll throw in with the brake hose camp... a collapsed brake hose will definitely yank you to one side or the other. A Fordification said, it's not something you can see from the outside.

I've had this happen on a couple different GM products. Basically, the collapsed hose restricts flow to and from the wheel cylinder - so when you step on the pedal after driving a bit the good side gets its fluid first while the collapsed side is constipated and can't squeeze it through the line... you wrestle with the steering wheel while the the slow side plays catch up.

Once the slow side gets some pressure on it, it'll keep some of that and maybe the next few stops are OK because there's enough fluid in there to operate the cylinder.

In really bad cases, you may be constantly fighting a steering pull because not only is the fluid arrving late, but it sticks around (at pressure) for longer periods of time as well - basically the cylinder can't back itself off (reverse constipation?).

My worst case was an '81 GMC - it pulled right all the time, until you pressed the brake... then it would yank left for a split second and slowly start pulling right again. If it was raining out, there would be heavy steam pouring from the right front wheel because the brakes were getting so hot. The truck also felt like it was constantly driving with low air pressure in the front tires.

I replaced both brake hoses - suddenly it braked straight, stayed straight, and I gained almost 5mpgs because the brakes were "free" instead of staying partially engaged all the time.