Brakes.....revisited

[Gbalko]

I have read the brake forums several times and I need some clarification. I currently have 9 inch front rotors and drums in the rear. I am planning on upgrading to wilwood discs in the future but right now I just want to get the brakes working as I have a bad diaphragm in my brake booster. Double venom suggested that a 1985+ corvette master cylinder would work for my current and future setup. DScott was apparently using an 1976 corvette master cylinder that when I cross referenced was for a manual brake system but he was using it with the Mustang II brake booster. Can anyone tell me which one is right so I don't make a fatal error?

[joyridin']

I am not sure which is correct, but a manual master from that year Corvette was $20. I see they are $34 now, so not a huge mistake in dollars. The unit I had could not be used with a power unit as the hole where you put the stem to push the master on a manual was pretty deep. There is a ring inside so when you push in the stem, it locks in place. The one on a power unit is shallow and the stem from the power unit does not lock in place.

With drum rear brakes, I would not use this master unless you have an adjustable proportioning valve. The disk style master pumps a lot of fluid to the rear and could technically pop the rear wheel cylinder. I had a problem on my car with disk brakes as the calipers on the rear had really small pistons and the Corvette master pushed too much fluid to those calipers.

[74proii]

So my question would be why go to Wilwood, unless you are planning to go to like the 6R kit. Because weight of the brakes are not the issue. Sure yes, you can get more pistons, but then you are only going to use their rotors, pads etc forever. Then you restrict your wheel diameters. Better rotors. better compounds are more than adequate. For example switching just the pads from semi metallic to carbon metallic such as Performance Friction. In their test rig using an F150, he vehicle stopped 100ft shorter, merely by changing the pads. Brake masters, proportional valves and calipers are matched for a very good reason. When you start cobbling together components and throwing in a adjustable valve because everybody else does it is not the best or safest method. Especially when most people just adjust the valve until the rear bakes lock up and then "just back off a bit".

[74proii]

https://www.wilwood.com/PDF/DataSheets/ds715.pdf

[Gbalko]

And what about drums in the rear? Are they more than adequate?

Can anyone tell me about the corvette master cylinder? Will both the 1976 and 1985+ work?

[t walgamuth]

I'm not aware of any cars with disc front and drum rear that don't have a booster....that said it is all hydraulics, so anything that creates the right amount of pressure in the lines will activate the brakes. Someone smarter than me can do the calculations to be sure your master will create enough pressure for your brakes.

[SHTMDWN PA]

Any suggestion on a power brake booster to work with 11” Ford Granada front rotor, Jag vented disc rear?

[74proii]

It's not he booster that's the issue other that mounting depths, bolt patterns and actuation rods. They all just multiply force by using the vacuum to aid in actuating the booster, e.g. less force required to move the master cylinders internal piston. Master cylinders have different internal diameters which produce the force. Larger the diameter, the more force applied, basic fluid dynamics. Outlet ports vary in size, a few differ i diameter. There is nothing wrong with drum brakes, they actually hold better that disc. Where the disc brakes are better is in the front, because if you do not adjust front drums correctly you will dive to either side based on how they were adjusted. That is why heavy duty brakes,for heaver vehicles like station wagons use drum rears. Look at 2.5 ton military trucks, drum brakes to prove the point. Discs are easier to service, and have newer compound that hold up to heat better, thus less brake fade.

[74proii]

The stock mII is fine, smaller booster diameter. You could use later single reservoir from like a fox body or later, gut again now your fittings are different. Really just a mater of what brand/kind of parts you want to do.