I've searched and searched and read through a looooot of threads about prop valves but I am unable to find a concrete answer so far...

I upgraded my brakes on my 2G to the Evo 8/9 Brembos front and rear. I have JDM knuckles, 3G brake booster, 1 1/16" MBC and have replaced all the rubber lines with braided lines....also running 235/40/18 wheels.

Originally the brakes were AWESOME....so much stopping power.

Then I upgraded my suspension to the Koni yellows with 700 lb/in fronts and 350 lb/in rears.

The car was dropped to 5 1/4" all around measured from the pinch seam. Surprisingly the camber change wasn't as bad as I figured it would have been...only my rears need to be cambered back out a small bit. The change in handling and grip was insane. I cannot break the car loose in first gear at all anymore. Around a tight corner in the middle of a crazy rain storm I dropped the clutch hard with a full left turn and it simply will not break loose....just digs in hard and goes. High speed corners are super fun....its like its on rails now.

Anyways, with the suspension upgrade I noticed the braking improved a lot. It has decreased my stopping distances considerably. The weight transfer to the front is surprisingly high considering i have 700lb/in springs up there....the nose dives way more than you'd think.

With the weight transfer under heavy braking I am starting to get the rears locking up too soon and I am getting the dreaded rear-wants-to-rotate-around-and-become-the-front effect.

Not cool. Super scary the first time it happened. Now I have to modulate the pedal under heavy braking to get the max brake without the car trying to flip around. It still stops fast as fcuk...but I would like to reduce this effect and know I need to change the bias.

The issue I see with adjustable prop valves (like the Wilwood 260-11179 Proportioning Valve) is cars come with diagonally split brake ciruits (FR-RL and FL-RR).

I don't want to change the system to a front-rear circuit split and use the aforementioned valve due to the fact that the factory split really is the best safety wise.

So basically I need a prop valve (or 2 or 3) to try out and see if I can reduce the rear bias. I have read over and over that others have swapped out the prop valves after big brake swaps...but I am unable to find what prop valve they swapped it for.

The real issue is the suspension....it has totally changed the way the weight transfer occurs under braking so I don't think (could be wrong) its as simple as using the Evo 8 prop valve.

Does anyone know what prop valves have what % split front to rear?

At which point do the rears lock up? If it's when you're really really deep into the braking pedal effort you might be able to just fix your problem with a differente brake pad combination (higher bite up front, lower bite on the back).

You on the stock prop valve? Abs or non abs? You have the rear locking up then keep it that way, i have the non abs valve and brembos and i find the rears need more bias as my front lock up alot sooner! Because of this im now ditching my prop valve and system and going to use pedals with a bias bar instead as its what i need to get better F/R braking correct.

What pads are you using aswell as tires as they can also be a part reason as to it breaking loose on you.

Pad balancing is how I deal with it with my race car. Not sure how I would go about it on a street car other than a valve.

Actually I would sort the problem the same way. Porterfield R4S on the end that needs grip, and try HPS and HP+ on the end that needs to lose grip. The HP* pads have a uniform lack of grip at any temperature, and their cf/temp curve is quite similar to R4S, so that would be my suggestion. HP+ have more grip than HPS but they're both quite mediocre, so paired with R4S I think they would be a good match for the OP.

TSiAWD666 said:

Pad balancing is how I deal with it with my race car. Not sure how I would go about it on a street car other than a valve.

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Exactly the same unless the bias is too drastically different. Only change would be having the mindset that pads have to be kept to street duty. Using race compounds can result in worse brake bias as they work on a higher operating temperature which usually means mediocre braking when cold.

I am non-abs stock prop valve....and ya, its deep into the pedal effort. I'd say somewhere between 60-80% of the pedal travel is where it locks up the rears first. 80% for higher speeds and 60% for lower speeds.

I guess I'll try some diff pads and see if I can even it up a bit....good call there. Its an easy fix to just swap around pads instead of bleeding shiiit each time.