Add-on brake proportioning valve

[Rttoys]

Doing some autocross, I found that you jamb on the brakes and the fronts lock instantly. Unless you are in a panic stop on the street, you’ll never experience this. At autocross, you find out quickly that you cannot jamb down on the brakes. After doing some research, I decided to decrease the pressure on the front brakes and see how it goes.

I ended up buying a Wilwood adjustable proportioning valve #260-12627. It’s an adjustable valve so you can decrease the pressure as needed. This is a version that will keep all of your fittings metric like on the cobalt/goblin. You will also need a few brake lines (need extra Incase you goof), fittings, bender and flare tools. You will need a double flare and bubble flare tool.

Coming off the front line T, a quick 90* will mate to the valve, then just make a small line to the master. Depending on year you’ll need a m10 or m12 fitting on the master. The master is a double flare or standard flare, all others are bubble flares.

Now to the good stuff. Once adjusted, this thing is a game changer on the brakes. Mine are adjusted where the front barely lock. Doing this, the rears are actually working and working well. This thing flat out stops. The rear works as it should now and the whole car “sinks” down when it stops. The brake pedal needs a little more pressure to work, but the feed back is great now. It’s not a brick hitting the brakes.

a few others have done this and I’m sure they will chime in on things I may have forgot.

important stuff-
Lines 3/16”
bubble flare everywhere but master
double flare on master
M10 fittings (there’s a difference between double and bubble flare fittings)
Wilwood prop valve 260-12627

 

[Ark :D]

I like it. Someone should sell a brake line kit.

 

[Rauq]

Yeah I'm definitely going to do this. Thanks for writing it up!

 

[Rttoys]

I like it. Someone should sell a brake line kit.

I made 2 sets of brake lines. Going to test fit them this weekend, so it is possible for me to make more.

 

[TheDon]

Without ever seeing a goblin in person, is there any way to reach the knob after foot well and hood are on?

 

[ctuinstra]

Without ever seeing a goblin in person, is there any way to reach the knob after foot well and hood are on?

No. I'm sure one could plumb it to an area that could be reached if wanted.

 

[Ross]

Once you get the brake bias set up, is there any need to adjust it again? I mean it looks cool on the dash, but I wouldn't want someone to turn it on me when I'm in a store.

 

[Rttoys]

Where I put it, no. At least not from sitting in the dr seat. You can dive through the pass seat area and reach it or from the dr suspension area, if you have skinnier arms, but not on the fly sitting in the dr seat.

When testing, I left the hood off, so I could reach it easier. I went from all the way out (most restriction on the front) and it was too little. A couple of turns in and it felt better, then one more turn in felt great. I ended up leaving it there until after my first autocross, then made another adjustment and thats where it’s at now. so far it has been a set it and forget it thing.

 

[Rttoys]

I mean it looks cool on the dash, but I wouldn't want someone to turn it on me when I'm in a store.

ya, that too. That could get bad quickly.

 

[Lonny]

Some of the proposing valves have a jam nut. If you mounted it within reach you could lock it with a jam nut when not racing.

You could also mount it under the hood out of sight but within reach.

 

[Towerdog]

I made 2 sets of brake lines. Going to test fit them this weekend, so it is possible for me to make more.

I would be interested in a set as I only have single and double flaring tools and would rather not buy a tool to use once.

 

[k.rollin]

The P2 build had a proportioning valve attached to the shifter to adjust the rear brake bias, but that car also had 10" rotors all around instead of 11" rotors in front, so the rears were locking up first without the valve. I have a picture in my email somewhere.

 

[Waterdriver]

Once you get the brake bias set up, is there any need to adjust it again? I mean it looks cool on the dash, but I wouldn't want someone to turn it on me when I'm in a store.

For most driving you wouldn't need to touch it once its set.
If your tracking your car, it might be nice to make adjustments on the fly. Adjusting for lack of surface grip or to aid in getting the car to rotate. (Moving bias towards the rear)

 

[Brian74]

I’m going to add one. Trying to figure out how to route a new front brake line to make it accessible from the driver’s seat.

 

[Carbon Soul]

I've been thinking of using an arduino for some telemetry. I bet you could set one up with a encoder on the dash that would send signals to the arduino, which would turn the brake valve.

 

[Scott #321]

Added a proportioning valve. Like many I did not wish to purchase a bubble flare tool for a single use and could not locate one for rental or to borrow. Purchased a 12 in line (CNE-312) and bent the existing line and new line as shown. Valve is hidden but adjustable without raising the hood and the plumbing was only 6 bucks.

 

[Rttoys]

Nice. How was the test drive?

 

[Scott #321]

I wish still waiting on wheels/tires.

 

[Rttoys]

Lol ok. Hard to drive it without that.

 

[Ark :D]

I think I need to do this. I had my first "under duress" hard brake today when an idiot 4 cars in front of me, decided to turn left without signalling. Needless to say, the three other cars in front of me slammed on their brakes at the last minute, and so did I ... left two nice long, thick patches of rubber with the front tires.