Flex lines off master cylinder and do I need a proportioning valve?

[JoshT]

So back so slowly working on my V8 swap project and am quickly approaching the brake system portion. Already got most of my brake system squared away.

Cobra 13" brake swap
Explorer 8.8" Disk Brake axle (98 Explorer)
Explorer Master Cylinder (also 98 Explorer)
Explorer 5.0L brake booster (IIRC, or maybe 4.0L Ranger?)
All new Ni-Cop hard line in front and to rear axle
New hoses all round

Next step on the project will actually be running new fuel hard lines down the frame rail to a rear mounted tank. While routing and mounting I also want to get my brake hard lines done before setting the cab back on the frame.

I know on old pre-abs trucks with drum brakes a proportioning valve is used to adjust pressure of the rear drums relative to the front disks. IIRC this proportioning valve was necessary because disks operate at a higher pressure that would cause the drum brakes to lock up. Since I'll be running disks front and rear I'm thinking that a proportioning valve is no longer necessary, am I right?


I know that it is necessary to allow for flex between the master cylinder (or prop valve if used) and the frame. I know that one acceptable method to allow for this flex is to make a coil of brake tube where it comes off of the master cylinder. Is there any reason that I couldn't/shouldn't use a steel braided brake line from the master to the hard line in place of the coil? I'd still be running hard lines down and across the frame, but a flex hose would make for a lot nicer installation and easier maintenance than the coil.

 

[bobbywalter]

a quality aftermarket braided flex line will work fine.


Ideal is as little soft line as possible in the system. but the harder nylon-ish braided flex lines are decent for these applications.


residual pressure is also a key factor for the rear brakes in regards combination/proportioning valves. even with disks in the rear you may need a proportioning valve. the weight transfer is most of the issue combined with this type of vehicles normal weight bias.

I would do just what you are doing... run the explorer master setup for disk/disk. from there(assuming your not using an abs system) you may want to use a proportioning valve if the rear is locking up too much for your tastes...