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Hard Brake Pedal

Posted By: JT01

Hard Brake Pedal - 05/24/13 10:47 PM

I have a 69 Charger and installed a new SBBC brake system its disc on front drums on rear everything is brand new from front to rear including the lines my pedal is very hard to push and only moves just a little bit. I checked the vacuum and it has 16 inches of vacuum Ive put 2 new boosters on it with the same issue.Whats going on here with this thanks for any help.
Posted By: radar

Re: Hard Brake Pedal - 05/24/13 11:39 PM

How much vacuum is the booster seeing?

Is the m/c bore too big?
Posted By: RapidRobert

Re: Hard Brake Pedal - 05/25/13 02:16 AM

I'd check how much clearance you have between the rounded nub on the end of the pushrod coming out of the booster & the bottom of the M/C rear piston (thimble). Want ~.060" or a bit less. Might crack a corner bleeder (either side) on the front then on the rear (seperately) & see if you get a full stroke. Might work the pedal & have a helper see how the front calipers are acting & might take off the rear drums & same deal but just a moderate amt of pedal travel when the rear drums are off so he dont pop the rear wheel cyl pistons out
Posted By: DoctorDiff

Re: Hard Brake Pedal - 05/25/13 05:57 AM

This is a common problem with SSBC brakes.

You probably need a 15/16" bore master cylinder.
Posted By: a493demon

Re: Hard Brake Pedal - 05/25/13 06:03 AM

if you take off the master cyl. from the booster the rod should be adjustable , the rod might be adj. out too far try turning it in and see if that helps.
Posted By: JT01

Re: Hard Brake Pedal - 05/25/13 02:07 PM

Quote:

if you take off the master cyl. from the booster the rod should be adjustable , the rod might be adj. out too far try turning it in and see if that helps.


Allready did that never changed anything
Posted By: DoctorDiff

Re: Hard Brake Pedal - 05/25/13 04:20 PM

What master cylinder are you running?
Posted By: JT01

Re: Hard Brake Pedal - 05/25/13 04:38 PM

The one that came with the ssbc kit. Should I get a different one.
Posted By: DoctorDiff

Re: Hard Brake Pedal - 05/25/13 04:54 PM

I don't think SSBC provides the correct master cylinder with their brake kits. Measure the bore size to confirm.

You need a 15/16" master for a '73-'75 A-body power disc brake application.
Posted By: JT01

Re: Hard Brake Pedal - 05/26/13 12:02 AM

Quote:

I don't think SSBC provides the correct master cylinder with their brake kits. Measure the bore size to confirm.

You need a 15/16" master for a '73-'75 A-body power disc brake application. [/quote. Where can I get one of these master cylinders and is it a 2 bolt application
Posted By: RapidRobert

Re: Hard Brake Pedal - 05/26/13 12:21 AM

An 89 Dakota 15/16" M/C would be a 2 bolt app. The 73-75 A body 15/16" app would not
Posted By: John_Kunkel

Re: Hard Brake Pedal - 05/26/13 12:30 AM


Be sure the booster pushrod isn't preventing the rear piston in the MC from fully returning. If the pushrod is adjusted out too far the rear piston won't allow the fluid to return to the reservoir and you'll get a hard pedal.
Posted By: JT01

Re: Hard Brake Pedal - 05/26/13 12:58 AM

Quote:


Be sure the booster pushrod isn't preventing the rear piston in the MC from fully returning. If the pushrod is adjusted out too far the rear piston won't allow the fluid to return to the reservoir and you'll get a hard pedal.


We adjusted the pushrod all the way in and it still has a hard pedal
Posted By: JT01

Re: Hard Brake Pedal - 05/26/13 01:06 AM

Quote:

An 89 Dakota 15/16" M/C would be a 2 bolt app. The 73-75 A body 15/16" app would not


Would this M/C have the lines going in on the drivers side
Posted By: RapidRobert

Re: Hard Brake Pedal - 05/26/13 01:08 AM

I would think so but I'm not sure. I'd have your parts house pull it off the shelf & let you know
Posted By: JT01

Re: Hard Brake Pedal - 05/26/13 03:52 AM

would this work http://www.ebay.com/itm/380584877050?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
Posted By: JT01

Re: Hard Brake Pedal - 05/26/13 04:37 PM

I also found this one and could buy a adapter plate to make it work. Let me know guys if any of the se I listed will work thanks. http://www.jegs.com/i/Right+Stuff/965/DBMC15/10002/-1
Posted By: John_Kunkel

Re: Hard Brake Pedal - 05/26/13 06:57 PM

Quote:

Quote:


Be sure the booster pushrod isn't preventing the rear piston in the MC from fully returning. If the pushrod is adjusted out too far the rear piston won't allow the fluid to return to the reservoir and you'll get a hard pedal.


We adjusted the pushrod all the way in and it still has a hard pedal



You still need to make sure the rear piston is returning. With the lid off the MC, have somebody gently depress the brake peddle and look for a burble of fluid on the fluid surface in rear reservoir....if no burble the piston isn't fully returning.
Posted By: DoctorDiff

Re: Hard Brake Pedal - 05/26/13 07:49 PM

Loosen the master cylinder mounting nuts. If the unit springs forward, the input rod must be shortened.

I can provide a new, aluminum 15/16" bore master with billet adapter for $100, or a new, 4-bolt iron version for $75.
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