Brake pedal is really stiff

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Is the pedal just as hard the next day on the first pump?
 
Revhendo said:
Is the pedal just as hard the next day on the first pump?
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There isn't really any pumping action to it. There's about an inch of pedal play and then it's damn near as hard as a rock after that. It's not like my Duster where first thing in the morning the pedal travels farther than normal. Once I back out of the driveway and head down the street, the pedal is back up to normal. This Valiant pedal is just the same no matter what.

I'm going to replace the front shoes and get a smaller bore MC and see what happens.
 
ESP47 said:
There isn't really any pumping action to it. There's about an inch of pedal play and then it's damn near as hard as a rock after that. It's not like my Duster where first thing in the morning the pedal travels farther than normal. Once I back out of the driveway and head down the street, the pedal is back up to normal. This Valiant pedal is just the same no matter what.

I'm going to replace the front shoes and get a smaller bore MC and see what happens.
Click to expand...

I was going to suggest checking for pedal pushrod length. I think someone else had mentioned the pushrod being engaged in the master cylinder properly. I was thinking it could just be building pressure without fully releasing. If you crack a bleeder, does it just dribble out, or more of a squirt?
 
I don’t think it is a master cylinder diameter problem. I have manual K&H disks on the Dart and same general sized diameter MS, and the brakes work & feel normal. My pedal is solid and firm once friction material contacts metal.

Granted on car equipped with power brakes there is a mushy soft feel before engine is started, and a bit of dead zone pedal travel when car is running as friction material contacts drum or rotor. Manual brakes give a much more positive direct feel without the vacuum assist acting as a middle man when compared to power brakes.

I still think you have an obstruction in the system, and need to blow out all the steel lines, and replace your soft lines.
 
you prob have a combination of small bore, 7/8 wheel cylinders, where 15/16 is avail, and a larger bore M/C.. where a smaller bore is avail, . . that'll give you a super hard pedal..

I saw several posts asking you to measure m/c bore size,, did you ever measure it??

and for the heck of it,, pull a piston outta your wheel cyls.. I bet they're small.. jmo
 
Re MC sizes. I just checked that recently for my cars. rockauto.com shows a 1"D bore MC for both my 65 C & A bodies, whether manual or power brakes. A bit strange because I recall reading that A-body power brakes should have a smaller MC bore. While that sounds opposite, A-bodies have a lever in the stand-off brackets that decreases the force on the MC.

I was concerned because I used an MC from a 99 Breeze in my 2 A-bodies, with a 7/8"D bore and was worried about too much pedal travel, i.e. maybe bottoming out on the floor. I didn't measure, but maybe 1-2" pedal travel in my Dart w/ power assist, which feels fine. I worried after I investigated an ebay ad for a new alum MC for a Volare w/ manual brakes for $25. Turns out those have 1.125" bore, which is much larger than mine. Indeed, not sure how that works since all Volare's were front disks. Volare's must have had large pistons in the calipers to match.

Most people would consider a stiff pedal to be great, assuming it doesn't take too much force, which sounds OK in your current configuration. Another way to get a little more motion like you desire without changing MC or wheel cylinders is to use DOT 5 (silicone) fluid, since it is more compressible (why one can't use w/ ABS). It eliminates rust in the brake system and won't eat your paint if it leaks, but does cost more.
 
I've blown all the lines out but I didn't take the distribution block out and mess with that yet.

The MC is 1" bore. I've checked that already.

The wheel cylinders I put in it are

Raybestos WC34876 in the back
Raybestos WC37102 and 03 in the front.

When I bought them I went on RockAuto and got the 9" brake wheel cylinders but they don't say what the bore size is. I've tried researching it and the only info I've found is ebay says the fronts are 1" bore and the rears are 7/8" but I don't know if I trust that. Does anyone know what bore size these cylinders are?
 
You lucked out because I am just now upgrading the 9" drum brakes in my 64 Valiant. Parts from rockauto.

The rear calipers are Raybestos WC34876 (x-ref Bendix 33504). They measure 0.810"D bore = 13/16"D.
The front calipers are Bendix 33242 and Centric 134.63008. They measure 1.00"D.
These are the same dimensions that rockauto lists.
 
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