These are what are called self energizing brakes when rotating forward,
meaning that the way the shoes and hinge points are set up, once
one of the brake shoes contacts the drum, it tends to want to "draw
itself into" the drum. There are springs in the system to retract
the shoes away from the drum when the brakes are released.
This is done to reduce braking effort and pressure requirements.
This is why the hydraulic piston on a drum brake system is so much
smaller than the caliper piston on disk brakes. Disk brake pads
actually move very little and release as soon as the pressure is
removed.
If the brakes are dragging, either they are adjusted too tight (typical
is to adjust until the shoe contacts the drum and then back off seven
or so notches), the release springs are weak, or the shoes are so
gummed or rusted up that they can't freely release. It could also
be that your power brake system includes a residual pressure valve
that keeps 10 PSI or so on the rear hydraulics which could work against
the release springs. Look in these areas and you will find the brake
problem.
One other thought, could the parking brake cable be too tight and
cause the rear brakes to drag?
Bruce K
57 3200
Mt. Iron, MN
At Tuesday, 10 September 2002, you wrote:
>Sorry I haven't been following this thread. If this has been covered I
>apologize. Have you checked to see if the rubber hoses are good.
I know they
>can get weak and expand during braking and then hold pressure afterwards
>making the brake stay on. Check for any bulges in the flexible parts
of your
>brake lines. It seems like it would be both back brakes though if
this were
>the problem on an old truck.
>
>Bill Schickling
>
>-----Original Message-----
>From: owner-oletrucks@autox.team.net
>[mailto:owner-oletrucks@autox.team.net]On Behalf Of Carl & Becky Ham
>Sent: Tuesday, September 10, 2002 12:50 AM
>To: boteler@olg.com; oletrucks@autox.team.net
>Subject: Re: [oletrucks] TF Rear End Rebuild Parts NOW Brake Problems
>
>Thanks Mike, as it turned out the bearings and brakes are fine.
At first I
>thought the shoes were set too tight on the drivers side. I removed
both
>brake drums, cleaned everything up, roughed-up the shoes with sand
paper,
>then reinstalled the drums and reset the clearance.
>
>Took it for a short drive and darn! the driver's side rear is hot
again!
>Checked all four wheels, the only one that's hot is the passenger rear.
>Haven't driven the truck much since a local repair shop installed
the power
>brake conversion earlier this year. They DID tell me they had trouble
>getting the brakes to work correctly and had to make some new lines and
>connections. Also noticed during the drive that at hard braking
the truck
>wants to pull to the right/passenger side. Can't understand whats
wrong!?
>Anybody else have problems like this when they went to power brakes? I
>brought the booster/master cylinder kit from Brothers (mounts under the
>drivers floor just like the original), and plan on contacting them
tomorrow
>to see if I missed something.
>
>Anybody got any thughts or suggestions? Would appreciate the help.
>
>Carl Ham
>'56 Chevy TF stepside
>Pontiac, IL
>
>>From: "Boteler" <boteler@olg.com>
>>Reply-To: "Boteler" <boteler@olg.com>
>>To: "OLETRUCK list" <oletrucks@autox.team.net>, "Carl & Becky Ham"
>><the_hams@hotmail.com>
>>Subject: Re: [oletrucks] TF Rear End Rebuild Parts
>>Date: Mon, 9 Sep 2002 23:53:36 -0400
>>
>>You should be able to get all of the brake/bearing parts from NAPA.
>>
>>Good Luck,
>>Mike Boteler
>>'56 8400 Wrecker
>>
>>
>>----- Original Message -----
>>From: "Carl & Becky Ham" <the_hams@hotmail.com>
>>To: <oletrucks@autox.team.net>
>>Sent: Sunday, September 08, 2002 8:42 PM
>>Subject: [oletrucks] TF Rear End Rebuild Parts
>>
>>
>> > Just got my '56 Chevy 1/2 ton back on the road after 3 months
of work.
>> > After driving it for several miles at highway speed (40-60 MPH),
I've
>> > noticed the driver's side rear brake drum (repainted during
my earlier
>>work)
>> > has most the paint burnt-off and the drum/wheel is hot enough
to fry
>>eggs
>>on
>> > after a short trip. I loosened the brake adjusters on the drum
but it
>>still
>> > gets hot after a short drive. My truck has the stock rear end with
>>either
>> > 3.90 or 4.11 ratio.
>> >
>> > I'm going to pull both rear wheels and drums tomorrow and I'm
hoping the
>> > problem is the brakes. But if it is not, does anyone know how
difficult
>>it
>> > might be to buy new rear axle bearings and where I might get a set?
>> > Appreciate any advice and thanks in advance.
>> >
>> > Carl Ham
>> > '56 Chevy TF Stepside
>> > Pontiac, IL
>> >
>> >
>> > _________________________________________________________________
>> > oletrucks is devoted to Chevy and GM trucks built between 1941
and 1959
>>oletrucks is devoted to Chevy and GM trucks built between 1941
and 1959
>
>_________________________________________________________________
>oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>
===================================================================
EASY and FREE access to your email anywhere: http://Mailreader.com/
===================================================================
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
|