Building 4 wheel disc system from scratch, all input welcome

[FLYNAVY53]

Hi guys. This winter, Im going to be completely gutting the brake system on this guy:



My 1972 C20 Suburban. Its my 3 season daily driver that I built three years ago with a 6.0L iron block LS and 4L65E. Initially it was a factory disc/drum set up. In the process of building the truck, I found some brackets that allowed you to mount the factory D52 front calipers to the rear along with the factory front discs. I went ahead and made the "upgrade" and have been running the set up ever since. It works relatively well, but given the fact that Im still running the original proportioning valve, its probably not ideal.

My plan at the moment is to retain the factory discs at all four corners while using the Wilwood D52 replacement caliper #120-10936 in the front. This gives a piston area of 6.28 inches and a pad volume of 3.9 inches. For the rear calipers, I was planning using # 120-10938, which is a similar caliper but with a piston area of 2.46 inches and a pad volume of 3.9 inches. Ill be running 100% new stainless line with -3 fittings. I was planning using the Baer "Remaster" master cylinder, mostly because I prefer the screw on servicing ports, the low profile integrated proportioning valve, and the fact that I can spec it with outlets on the right side of the unit. Ill retain the factory brake booster and pedal assembly with its 5.6:1 pedal ratio as it was previously a boosted set up.



My biggest question is what bore size should i be running on the master cylinder? Additionally, any other comments or suggestions would be greatly appreciated. Obviously this isn't a track car, its just a fun daily driver that sees a lot of miles. I want it to be capable and reliable. I do a lot of road trips up through the smokey mountains and some of those down grades were particularly taxing on the more or less factory brake system this summer.

All input is greatly appreciated!

[1989GTA]

Normally with a booster you would run say a 1 1/8" master cylinder. What brakes are on the front? Are they D52's? Also what size rotors are on the front? Regarding the proportioning valve, I would just buy a disc/disc version.

[FLYNAVY53]

Currently has stock, single piston, D52s at all 4 corners. They're 10 inch rotors on all 4 corners.

[Skip Fix]

Look at '96 Impala SS/Caprice D614 pads they fit the D52s but have a bigger pad area.

[andrewb70]

I hate to say this, but what's wrong with the stock drums in the rear?

Andrew

[FLYNAVY53]

Well, the rear drums were replaced with the same discs as the fronts 3 years ago. The issue is that he bias is off for two reasons....first the front and rears are the exact same calipers, plus the proportioning valve is still the original unit from the disc/drum set up. The idea here is to use the Wilwood D52 replacement calipers that have the same pad volume front and rear but different piston area, in combination with a proper proportioning valve to achieve the proper front to rear bias.

My biggest question, is what is the right size master cylinder for this set up? Based on the research Ive done, it looks like 1 1/8 is probably the way to go.

[Skip Fix]

614 pads will fit Wilwood D52s.
Pretty sure the standard 2 15/16" piston D52 will have more piston sq in than the Wilwoods largest dual piston version.

79-81 Trans Am 4WD used a D52 front and a D154 rear(basically with ratchet E brake built in) and used a 1 1/8" MC with a 9" dual diaphragm booster.

[Peter Mc Mahon]

I think pad coefficient is what you care about not surface area

[Skip Fix]

There are a number of 614 performance pads available also. Hawk has some. Now I bought some of the heavy duty Wagners to look at and they looked like a lot of metallic in them but just have an EE rating.