More rear brake bias needed

[mitsuturbo]

I've come to realize, after riding in some other peoples' cars of different makes/models, both new and old, that my rear brake bias seems to be lacking. I assume the 13" wilwoods up front likely exacerbate this. I've been looking into a rear prop valve, but due to the diagonal configuration of the factory proportioning valve, and a 1:1 A/B configuration from the master cylinder, i may want to delete the booster, install a Wilwood master cylinder with a 2:1 A/B configuration, and an adjustable proportioning valve to modulate the rear better, especially for AutoX duty.

I'm unable to find any info posted anywhere regarding the factory brake pedal ratio. I'll have to measure it myself, i suppose.

Has anybody on here done an aftermarket Master Cylinder and prop valve? I'm not looking to go with a dual master, moving seating position back, modifying firewall, or extending a steering column for a full on "race car" setup, but something a bit more simple yet effective. The dual master thing is something i'd only want to do around the time i decided to put a cage in the car and take it to a track on a trailer... Which will not likely be ever.

It SEEMS like a chasebays booster delete kit and a tandem MC from wilwood would work wonders, provided i have a decent pedal ratio. I'd expect SOMEBODY has done something like this with these cars, right?

 

[slugsgomoo]

I think I'm the first to be doing a manual brake setup, and right now it's just parts in the garage, which I know isn't super helpful.

My setup is a billet plate from Jake Lehmkuhl (has an insanely built 2g hill climb race car), twin Tilton master cylinders, and a wilwood balance bar. I don't remember what the sizes were off the top of my head, but they were calculated based on the Wilwood BSL6 fronts, and BSL4 rears that I'm running. My main reason for not having it installed yet is I need to make new lines and eliminate the prop valve, and I felt like that would be much easier with the engine out of the car.

 

[mooserage]

I admittedly need to read up more on these types of brake setups, but I was wondering, slugs, why the two master cylinders instead of a proportioning valve?

 

[slugsgomoo]

In order to have a margin of safety, you need two have two separate systems, which is why the OEM system though in line has separate feeds & outputs, and there are technically two masters (even though the arrangement is inline). From here: MPBrakes writeup about single vs dual

Quote:
Dual reservoirs came about simply from a safety standpoint. A single reservoir master cylinder is providing pressure to both the front and rear systems. Should a failure exist or happen in the master cylinder, there is a very good chance that all brakes will be lost in the vehicle. With a dual reservoir system that splits the car into front and rear, you stand a chance should a failure occur.



In our cars, I believe each master feeds into the prop valve, which then sends the fluid diagonally (i.e. LF&RR, etc). In my new setup the smaller master will send the fluid solely to the rears, and the larger master will send it to the fronts. Then the balance bar allows setting bias so you can achieve the front:rear ratio you want.

 

[mooserage]

Thanks Slugs, that makes perfect sense and thanks for the link. I forgot that the OEM MCs were internally separated. I can also see how that setup will make the F/R bias adjustments much simpler compared to adapting something to the the OEM setup, especially with the diagonal prop valve that was used.

Sorry to take the thread off topic, but appreciate the explanation!