Wilwood Pedal Box and Proportioning Valve

[BrianToronto]

So I have the Wilwood pedal box, with 3x 3/4" master cylinders. It includes a balance bar to proportion front/rear brake application. I'm thinking I should install the Wilwood proportioning valve anyways for easier front/rear balance adjustments. So my question is how easy is it to use the balance bar adjuster or should I do both? Who's using both?

[skullandbones]

Brian,

I eventually discussed this same process with a Wilwood technician a couple of years ago. I don't know if Wilwood decided using the balance bar for bias was originally a good idea and changed their mind later or if their policy has always been as he related it to me. He said only use the balance bar to adjust bias very little. He said install the necessary MC to add the necessary bias to the system. Since there are so many variations that people use due to "donor" or other aftermarket choices, it can be rather complicated. Best to get a matched system throughout that works on the roadster.

Personally I have a slightly smaller MC in front (I think 5/8 ") and 3/4 " in the rear. I have a proportioning valve on the rear circuit. My balance bar is perpendicular to the push rods. I found that if you add too much bias it can cause the components in the MC to wear abnormally (assumption). I took the one apart that was leaking after a rather hard track day and did not see any damage but it definitely leaked after that day of banging on the brake pedal over and over before the curves. The instructions I had from Wilwood talked about the angles of the balance bar and gave specific tolerances which I tried my best to follow on original install and induced bias to the front (again assuming that would apply more pressure on the front MC). After I spoke with Wilwood more than once , I set it up with no bias and the different MCs. FFR also changed their kits eventually from the 2 3/4 MCs to what I have (I think). BTW: I haven't actually used my proportioning valve yet but it's there if needed. I like having adjustment in systems even if you don't use it much. This balance bar thing bothered me from the very beginning. So when I found a solution, I feel much more secure with my system.

Good luck,

WEK

[BrianToronto]

This is massively useful feedback. Thank you so much skullandbones. My brakes are the Wilwood calipers/rotors all round (I think 14" front with 6 pot calipers and 12.88" with 4 pot rear). I'll go with adding the proportioning valve on the rear circuit then. The 818 manual shows the circuit on the front brakes which makes even less sense. I have to same, the manual has been a bit of a disappointment on this build.

[Mitch Wright]

Personally I wouldn't use and don't see the need for the additional proportioning valve. I agree with WEK make sure your masters are sized correctly for the calipers you are using.
I have AP 4 pot calipers and rotors on my car front and rear, Wilwood pedal box 3/4 masters (happen to be the correct size for my application) and a brake balance knob attached to the balance bar. I am just a 1/2 turn off center (to the front) on the balance bar, I have impressive brakes that can be adjusted on the fly.

[flynntuna]

This is massively useful feedback. Thank you so much skullandbones. My brakes are the Wilwood calipers/rotors all round (I think 14" front with 6 pot calipers and 12.88" with 4 pot rear). I'll go with adding the proportioning valve on the rear circuit then. The 818 manual shows the circuit on the front brakes which makes even less sense. I have to same, the manual has been a bit of a disappointment on this build.


If your using the stock wrx calipers, then the porportioning valve should be used in the front circuit because the rear calipers are basically too small for a midengine car.
There a lot of threads discussing this and ways to improve this situation.
Putting the valve on the rear circuit will make a less than ideal set up worse.

[BrianToronto]

Ahhh - that makes more sense. I'm thinking I'll go without the proportioning valve then and make the small adjustments with the balance bar. 6 pot front, 4 pot rear on 12.88" rotors should provide plenty of rear stopping power but doesn't sound like it will need to be dialed down.

[EODTech87]

With the larger rotors and 6 pot fronts you'll lock the fronts before the rears so you'd want the valve on the front. There is a thread somewhere that everyone discussed brake bias and it was basically determined that it's very close to 50/50 and the same front and rear setup was preferred.

[skullandbones]

I apologize about not noticing this was an 818 setup. The weight distribution for the 818 is much different than the roadster. However, the comments about the balance bar and such hold true. We actually did many panic stop tests (with observers at the point of braking) to confirm that the roadster I have needed more bias to the front with my initial setup with 2 3/4 inch MC. I would recommend similar testing. It's a lot of fun too!

Good luck,

WEK.

[mikeb75]

Speak with Wilwood tech support about MC sizing for your calipers. I run 4 pot Wilwood fronts with OEM rears with the 2 MC Wilwood pedals and balance bar/adjuster. The tech support line was able to recommend the correct MC bores for my setup so I only need the balance/adjuster for fine tuning.