brake proportioning valve

[Chickenman]

4 hours ago, Richard McDonel said:

Chickenman,

 

I'm not clear on gutting the prop. valve.  With only two connections ( M and R), I don't see how we would achieve a "T."  Would it not make more sense to simply remove the factory valve and install the Wilwwod in its place?  

Best regards All

 

You gut the insides because you cannot have two hydraulic proportioning valves in series. Creates problems with long pedal travgel. You could plumb the WilWood prop valve in place of the factory valve. Depends where the factory valve is located. Meant to say " Coupler " not a Tee. Sorry. 

[sweatybetty]

7 hours ago, Chickenman said:

Not really.  That can create problems in the Dry. You get more weight transfer to the front under dry Road conditions.  That requires less braking force from the rear brakes. From us PNW Road Racers who always race in the Wet, you actually crank in more rear brake bias  ( Wet ) because you don't get as much weight transfer to the front..

Setting the brake bias up for maximum braking in the wet, can cause the rears to lock before the fronts when it's dry.  That's a good way to spin out.  An in-Cockpit knob for Race cars alleviates the problem somewhat.  But for a street car with the proportioning valve in the engine bay, it's best to set up Brake bias in the dry. 

Hill climbs also allow more rear brake bias as you're going uphill and the rear wheels have more weight on them under braking than when on a flat road.. or a downhill. I'd typically have to add a full turn of rear brake to my Camaro when I ran Hillclimbs as compared to Autocross or track days. And I liked a LOT of rear brake. 

Modern race cars such as F1, Indy Car and WEC have brake bias controls on the steering wheel. and the drivers will adjust them constantly for different types of corners ( Road racing ). You can often see the driver twiddling with knobs or buttons before a corner and see the Dash flash up numbers like 63.2,  63.0 etc. That's the brake Bias percentage. 

i would think better traction on dry pavement vs. wet

[Mark Maras]

 Here in the Pacific Northwest, I'd set it up in the wet.

Edited June 6, 2017 by Mark Maras

[Chickenman]

Well... considering that we just had 7 freakin' months of bloody rain here. You may have a point...  

[gnosez]

Actually a dry, dirt road is best as you can get a better idea of brake input from the plow marks the front and rear tires leave in the dirt.

You can also mark the tires with white shoe polish (one of the only words that changes meaning when capitalized) and have someone watch to see which tire stops rotating first.

[Chickenman]

2 hours ago, sweatybetty said:

i would think better traction on dry pavement vs. wet

It is. But It's all about weight transfer and balance. Grip levels are the same for front and rear Wet or Dry. It affects all four tires at the same time. The weight transfer off of the rear tires ( and to the front )  is less in the rain .  Less negative G forces under braking in the Wet ( obviously ) = less weight tranfer to front tire = rear brakes have more of a percentage of weight on them = more rear brake bias availble.  Part of the " Traction Circle " equation. 

[sweatybetty]

3 hours ago, Chickenman said:

 The weight transfer off of the rear tires ( and to the front )  is less in the rain . 

the rest of it i understand, but why does weight transfer drop in the rain? maybe you could pm me with this. dont want to hijack this thread

Edited June 6, 2017 by sweatybetty

[240260280]

GnoseZ gets his testing skills from a driver that often goes on the dirt shoulder to make things tougher on the guys behind him    thus the dirt road testing.

[Chickenman]

4 hours ago, sweatybetty said:

the rest of it i understand, but why does weight transfer drop in the rain? maybe you could pm me with this. dont want to hijack this thread

PM sent... 

[Richard McDonel]

I have brakes!

Thanks to "Grannyknot" (Chris) who replied to my May 24 post and offered me a clean, used proportioning valve, I now have brakes.  With neither my original valve nor the one I rebuilt passing fluid to the back brakes I was stuck.  I installed Granny's and it works.  Never before been so happy to see $$$DOT 5 brake fluid coming out of a bleeder.

Many thanks Chris. 

[Namerow]

Good to hear... but I'd still like to know how a proportioning valve turned into a no-flow valve.  The more I study the FSM (see below), the more it seems to me that the 'upper' seal is critical to the way the valve works.  It appears to have a unique cross-sectional shape.  Maybe you installed it upside down?

Edited June 20, 2017 by Namerow
FSM dwg added, with comments

[240dkw]

That is good news, I am sure after helping you take it apart and look at all of the parts that the MSA kit came with two "lower" seals and no "upper" seal. But why we could not get it to work using a mix of the old and new parts I do not have a answer for. Glad you are done fighting with it.