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Disc brake conversion = now brake pedal hits the floor (mounting issue)

Started by Corellian Corvette, October 24, 2007, 04:32:31 PM

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Corellian Corvette

Just when I think I'm around the corner on this disc brake conversion, something else comes up to drive me batty.  :'(

I'm using the MP brakes front and rear disc brake kit. Everything from the kit appears to be mounting fine.

I wasn't happy with the MPBrakes booster setup, so I sourced an original MOPAR Bendix disc brake booster. The pushrod was too long, so I had the unit rebuilt by Prior Remanufacturing and they shortened the rod.

So, I think I'm finally in good shape. I put the rebuilt Disc Brake booster back on, with the mounting plate, linkage, and brake pedal from the original drum brake setup.

NOW I HAVE ANOTHER PROBLEM  :brickwall:

With everything assembled, the brake pedal is VERY close to the floor. In fact, when I push the brake pedal down, it hits the floor well before there is complete compression of the piston. This is without any carpet or padding. I suspect that with carpet installed, the pedal would hardly have any travel at all!

So now I'm at a loss. Was there a different pedal hole for disc brake cars? Was the linkage under the dash different? I don't see any adjustments to make the pedal travel longer but maybe I'm missing something. Please help!

Thanks!

Just 6T9 CHGR

That is very strange.  The pedal assys are the same for power & manual.... Do you have the correct linkage?
Chris' '69 Charger R/T


Corellian Corvette

I'm using exactly what came off the car - it was a power drum car with the single diaphram booster - except I replaced the booster with a bendix dual-diaphram. All the same linkage and everything I put back on.

Does anyone have a correct rod lenght or a picture of their setup from a disc brake car?

bull

I hate to state the obvious but it sounds to me like the rod is too short now.

UFO

Was master cylinder bench bled?Rest of system bled?
Kind of like the toaster that doesn't work,step one -Is unit plugged in?

Corellian Corvette

Well you bring up an interesting point - I have not filled the MC with fluid yet. I did not see how that would affect the position of the pedal relative to the floor, but I'm not sure? I have no idea how the unit works relative to engaging the brakes - it's that the pedal is physically resting only a few inches above the floor, and can easily be depressed with a very short throw and hit the pan; and this is without any carpet or padding - with those I think the brake may just rest on the pad.

What is the correct lenght of a power disc brake pushrod on a correct Bendix Master Cylinder? That would help...

UFO

Cant help you with length of push rod.Pedal height on power brake cars is lower than manual brake cars.Since this is a hydraulic system with no fluid of course there is no resistance.


Just 6T9 CHGR

This is how the linkage is supposed to be hooked up....  The large bolt attaches to the pedal arm.

The booster rod to the M/C has to be adjusted when the master is bench bled & bolted to the booster....looking inside the wells of the master, when bolted up the piston should move ever so slightly so as not to uncover the ports at the bottom....if the rod is too far out & it pushes the piston inside the master past the ports, the brakes will drag......not enough adjustment you will have a spongy pedal....hard to explain but harder to understand from these crappy instructions as well...
Chris' '69 Charger R/T