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Spongy brake pedal with manual conversion

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Old 08-12-2016, 07:41 PM
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Default Spongy brake pedal with manual conversion

I converted my brakes to manual with aerospace rear drag race brakes and their master cycle. I've bleed the brake a dozen ways, except vacuum bleeding, and they still take one good long pump to get strong pedal feel. I'm told its the drag brake because they retract away from the rotor, then gotta make the distance back up.

Any ideas?
Old 08-16-2016, 06:03 AM
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It sounds like your master cylinder might not be the right size for those brakes (too small of a piston). Or, there's still air in there somewhere. If the master cylinder is too small (piston size) you can't move enough fluid to "activate" the brakes properly (you don't have enough fluid volume to push the pistons out of the calipers far enough to get the pads working against the rotors). If the master cylinder pistons are too large, you'll move a lot of fluid and have a very hard pedal and it will take a lot of force to get the car to stop. Somewhere in between is where you need to be.

Have you contacted Aerospace brakes to ask about master cylinder piston size? And are you running the factory front brakes with their rear brakes? All of this is stuff they are going to want to know. Their master cylinder might expect you to use their brake kits on both ends of the car, etc.

Edit: I see you have their rear kit and their master cylinder. I'm assuming this means stock front brakes. I would certainly call them and ask about that setup.
Old 08-16-2016, 10:10 AM
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could be the pedal ratio also. maybe move pushrod up on brake pedal for mechanical advantage?
Old 08-16-2016, 10:19 AM
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Here is some instructions from our kit that may help.
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