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At a minimum you need a dual master cylinder setup with a proportioning valve, and a couple other things with a disc/drum system. Takes different pressures, and fluid volume. The fronts might not be doing much with a single master cylinder.
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Registered Member
Sounds like you need to install an adjustable proportioning valve to set the rear brake pressure. I remember installing one on my 55 Chevy after installing a Dana 60 rearend back in the 80's.sum-g3905_cp.jpgSummit part # G3905.
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A lot of assumptions being made here.
What master cylinder do you have and what is the bore size? It should be 1" or smaller. Some brake conversions supply a 1-1/8" bore, but that should only be used with a booster.
What calipers do you have?
A proportioning valve is only going to help if the rear brakes lock up - which they should first.
Big tires and wheels only matter to this question if they are HUGE - like the tires on a lifted truck, etc.
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i dont know the answer to most of these questions. all gm stuff, including a dual cyl., proportioning valve.
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Sorry I can't help you much without much more detail, and pictures. I'm trying to figure out why I can't get the brakes to lock up on my 02 Camry beater, which probably had crappy brakes when new. Everyone needs good brakes. You might need to find a local professional, which could be infinitely cheaper than what could happen.
Last edited by 55 Rescue Dog; 07-27-2020 at 04:12 PM.
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Have you considered adding a power brake booster? Several different types available. Makes a lot of difference and all OEM disc brake applications use them. For a reason.
Just an idea,
Harry
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Registered Member
If the OP is having an issue with not being able to apply enough pedal pressure to generate stopping force, then I agree he should consider that, but to correct a statement Harry made in the prior post...
No, not "all OEM disc brake applications use them. For a reason." as Harry posted.
There were (and possibly still are) several factory OEM disk brake installations which used Manual brakes. The mid-late '60's 4-wheel disk brakes on Corvettes supplied both manual and power disk brake options (The manual versions used smaller diameter MC than did the PB option). I recall in the '69-70 time frame when I first began looking at NEW cars (Chrysler and Chevrolet), Chevelles... Roadrunners... Darts.. etc all provided for disk brake installations (front only) with a manual MC. I considered those at the time because the Power option was higher priced than the manual disk option and I had NO money!
I'm building my '57 Nomad currently using the big disk brake parts from a '96 Corvette and utilizing a manual MC from a '67-69 Corvette. Before I decided to go this way, I talked to several owners of trifives who were using a manual MC with disk brakes and were happy with them, although a couple did say that their wives didn't like the pedal pressure required.
Last edited by BamaNomad; 07-28-2020 at 04:41 AM.
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My 72 Cheyanne Super came with A/C & PS, but did NOT have power brakes. It stopped much better than the 64 Custom it replaces.
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Ratio?
I am currently building my 55 using Wilwood manual MC and their 12" big brake kit with 4 piston calipers. Wilwood said I need at least a 6 to 1 pedal ratio . 20200726_104645.jpg20200725_154419.jpg
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The stock pedal ratio is 6:1, so no mods needed there. Just use Wilwood's recommendation for master cylinder bore size based on the calipers you've selected. You probably need 7/8" or 15/16" with those, but don't take my word for it.
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