OT but hopefully interesting: single to dual brake line conversion Options

[Tdskip]

So I need to get this thing ready for a charity event and that includes new brake lines. I converted it to a two line, split front and rear, brake system for safety purposes but haven’t finish3s the hard lines yet.

I’m thinking having a proportioning valve in the system so I can adjust the front/rear bias would be a good idea but am not sure how to plumb that.

I have a conventional mid ‘90s Toyota dual M/C now.

Figured our racers here have dealt with that so thought I’d ask. For those that have done this where did you put the valve? I’ve seen two types - one where both lines from fhe MC go to a combination valve and splitter (pictured below, just an example I haven’t ordered this yet or decided to go this way) OR a set up where only the rear line goes through the valve.

Thanks in advance for any ideas and coaching.

[Superhawk996]

Just a quick word of advice from a former automotive brake engineer.

Race cars with bias valves are great for the track . . . not really a good idea for the street.

On track, too much rear brake and the car starts to get loose (i.e oversteer) but you have a skilled driver (hopefully (IMG:style_emoticons/default/biggrin.gif) ) sort of expecting it and plenty of runoff if he wasn't. On the track loads are more or less known, surface grip is more or less known, weather is known.

On the street grip is unknown, dry pavement, wet pavement, snow? New tires or nearly worn out tires?

On street loads are unknown (Frunk full tank of gas or empty)? Luggage in Frunk? Or, maybe you loaded the trunk with depleted uranium? Who knows & it varies trip to trip. These extra loads will dramatically affect how much bias you can put on the rear.

You have no opportunity on the street to "tune" the system for that day without risking your life.

More than likely, you'll end up setting it "safe" with way more bias to the front to keep things stable. Then you're giving up whatever you potentially could have gotten out of the rear with a proper proportioning valve.

No easy advice off the cuff on picking proper (fixed) proportioning valve without writing a dissertation. Use OEM is your best bet.

Side note: Diagonal split isn't out of the question and might be safer for your application. If you've ever driven a vehicle with both fronts failed, it's an eye opening experience.

In your FJ40 example, if you over bias the front on a front/rear split and then do fail the front circuit, you'll find you basically have no brakes. Short wheel base (FJ40, Jeep CJ) and high Cg will only make this exponentially worse.