1955 Super - Single Brake Lockup

[1955Buick]

Hi,

 

Once every 30 or 40 times I drive my Super, it gets into a state where, with just slight pressure on the brake pedal, one of the brakes locks up. I think the last time this happened, just as I was pulling out of a parking lot but before I applied the brakes, I felt a slight "drag" once per tire revolution. It made me wonder if the drum was out of round (?). Any ideas for how to diagnose? The problem appeared to correct itself after a few stabs at the power brake pedal.

 

Thanks

[EmTee]

First, I'd pull each drum (unless you know the offending wheel) and check for contamination (oil, grease or brake fluid) on the shoes.  It doesn't take much rear axle oil from a leaking axle seal to make the brake very 'grabby'.  If no leaks, look at the friction material and how it is attached to the shoe frame/backing.  Bonded shoes (no rivets) are particularly prone to separating from the steel backing with age.  Rust can form under the friction material and eventually 'pop' them loose.  If the leading edge comes loose, it will prematurely engage the brake on that wheel.

[SpecialEducation]

My first suspect in wonky brake operation is the flexible lines.  The internal layers of the hose will separate and fluid will get in and cause a bubble that acts as a check valve.  Fluid pressure goes down to the wheel just fine, but doesn't come back so easy.  Initially, the issue is usually intermittent, but gets worse as the hose continues to degrade.  I've lost count on how many times I've seen this over the years.

 

That said, I'm guessing that the '55 is like the '56, where there's a single flexible line going to the torque tube and it's all hard lines from there (3 flex hoses total).  Obviously, a bad hose here would affect both rear wheels equally.  

 

Which wheel is giving you trouble?

[trp3141592]

Hi,

 

I vote for a collapsed flex hose.  Been there--took a lot of thought to figure out the problem.

 

BTW, you can't tell from the exterior of the hose that the interior has collapsed.

 

--Tom

[60FlatTop]

If you can't slide a piece of #10 wire through the hose it is probably delaminated.

Bernie

[JamesBulldogMiller55Buick]

If it's not a hose issue

Could be a cylinder sticking. 

the wheel cylinders might need rebuilding (honing)