Proportioning valve to go with brake upgrade?

[lifespeed]

I've been reading about the various brake upgrade options available for our cars. But I have seen no mentioning of replacing the proportioning valve. Surely y'all aren't overlooking this critical step?

There is no way that more powerful brakes in the front will retain the same ratio of stopping force to fluid PSI. I know that when I upgraded my old '97 Crown Vic to the 'big' '98 brakes it was glaringly obvious the proportioning valve needed to be changed. The fronts locked up when I hit the brakes hard one time. I replaced the proportioning valve with a Wilwood unit immediately afterwards, and it worked perfectly.

[RR|Suki]

I know we have a lot of sad out dated parts on the car. With the brakes though they didn't stick with the bronze age tech, pretty sure it's all controlled electronically by the ABS system.

[fastblackmerc]

I've been reading about the various brake upgrade options available for our cars. But I have seen no mentioning of replacing the proportioning valve. Surely y'all aren't overlooking this critical step?

There is no way that more powerful brakes in the front will retain the same ratio of stopping force to fluid PSI. I know that when I upgraded my old '97 Crown Vic to the 'big' '98 brakes it was glaringly obvious the proportioning valve needed to be changed. The fronts locked up when I hit the brakes hard one time. I replaced the proportioning valve with a Wilwood unit immediately afterwards, and it worked perfectly.

I have the TCE brake upgrade on my MM with the rest of the stock system. No front brake lockup. I believe the ABS system controls it all.

[lifespeed]

Guys, I know the ABS works. But don't you realize that having the ABS kick in as a last-ditch effort to control wheel lock is not right? Under braking conditions other than near-lockup the balance of force front/rear affects vehicle balance and is controlled by the proportioning valve.

Any change to braking hardware has to address this. Like I said, I found this out from experience.

[lifespeed]

with the bronze age tech . . .

The Bronze Age ride isn't so bad. I convinced my brother he wanted one of these too, and he just bought a 2004. He loves the full size body-on-frame hotrod ride and handling. He commented the solid axle positraction thrust was "like his old Chevelle".

[musclemerc]

The only way I can see a use in changing out the PV is if the MC is upgraded to one that puts out more pressure, other that that it's not needed.


I use to build 90~93 mustangs and we often did the Cobra brake upgrade with a 5 lug conversion, it required swapping to a Cobra MC that was much bigger than stock so the PV was necessary because only 1 line went to feed the front brakes and the DS brake was naturally weaker than the PS.

[RR|Suki]

Guys, I know the ABS works. But don't you realize that having the ABS kick in as a last-ditch effort to control wheel lock is not right? Under braking conditions other than near-lockup the balance of force front/rear affects vehicle balance and is controlled by the proportioning valve.

Any change to braking hardware has to address this. Like I said, I found this out from experience.

No one said anything about the ABS itself kicking in. The ABS system controls brake bias electronically, which adjusts itself to keep the bias as it should be. If it was still manual valve someone would have noticed in the last 8 years.

Hell I'd have noticed a problem in the last 6 years of track events.

[lifespeed]

The ABS system controls brake bias electronically, which adjusts itself to keep the bias as it should be.


Really? OK, I'll admit this is my first ABS Panther platform car. But I'm not so sure you're correct.

Please reference the 'brake bias adjustment valve' part number or schematic diagram. Most ABS I'm familiar with takes action only under lockup conditions, pulsing the individual lines to the calipers. This would not be a mechanism for bias adjustment.

I'm always willing to learn, but your description of this additional function inside the ABS is not something I've heard of. Yes, the ABS can contain a hydraulic proportioning valve, and I believe that is where our cars locate it, rather than the MC. But I doubt it is adjustable, manually or electrically.

[lifespeed]

The only way I can see a use in changing out the PV is if the MC is upgraded to one that puts out more pressure, other that that it's not needed.


I use to build 90~93 mustangs and we often did the Cobra brake upgrade with a 5 lug conversion, it required swapping to a Cobra MC that was much bigger than stock so the PV was necessary because only 1 line went to feed the front brakes and the DS brake was naturally weaker than the PS.

The only way a PV adjustment is not need is if the ratio of braking force somehow remains unchanged with a caliper/rotor upgrade. The force is a combination of hydraulic pressure at the caliper inlet, the piston area, brake pad area and rotor diameter.

Did any of those parameters change? Then you changed the ratio of brake force front/rear, if you did not change the rears in a matching way. There is no need to change the MC pressure to effect a change in braking force. Otherwise the big brake upgrade wouldn't work with stock MC.

Now, I'll admit there is a possibility that you're not changing the balance much, to where it really screws up the car. I'm just saying I did a front-only brake upgrade to a '97 CV, and the results were very wrong. I also did not notice until a hard use situation on a car that did not have ABS to mask it.

Why do do you think Wilwood sells an adjustable proportioning valve? Why do race cars have elaborate dual-master cylinder setups with a balance bar? This is a real setup parameter on any car. My point is simply that it something to consider when messing with brakes, a key safety and handling system in the car.

And if you've been driving around a car with ABS and increased front brakes, I'm going to say the ABS helped you not notice it. I don't know Mustangs, but back then the MC usually contained the PV, so you could have had somewhat correct results because you swapped the MC and PV.

Disable the ABS and hit the brakes hard. You think those beefy new fronts aren't going to lock prematurely? Just from your experience hotrodding cars, this should be apparent.

[RR|Suki]

The whole point of the proportioning valve is to prevent lock up. So having it inside the ABS module (however it modulates) reacting to the wheel speed sensors would in effect be the same thing. . . The control is electronic, maybe not a complete description, or clear since I'm not a brake tech. Either way though the proportioning becomes a non issue. Like I say, if it was an issue it would have shown up by now.

[RR|Suki]

The whole point of the proportioning valve is to prevent lock up. So having it inside the ABS module (however it modulates) reacting to the wheel speed sensors would in effect be the same thing. . . The control is electronic, maybe not a complete description, or clear since I'm not a brake tech. Either way though the proportioning becomes a non issue. Like I say, if it was an issue it would have shown up by now.

PS I can count on one hand the number of times ABS as activated off the track. . . if it was an issue it would come on every time I brake hard.

[musclemerc]

The only varible I think your not considering is the electronic interface within the ABS controller. Race cars run a manual setup as I did with the Mustangs from back in the day. I'm just saying a PV upgrade is only necessary when the MC is'nt putting out enough pressure for the calipers to clamp properly. You have some valid points though. ;)



The only way a PV adjustment is not need is if the ratio of braking force somehow remains unchanged with a caliper/rotor upgrade. The force is a combination of hydraulic pressure at the caliper inlet, the piston area, brake pad area and rotor diameter.

Did any of those parameters change? Then you changed the ratio of brake force front/rear, if you did not change the rears in a matching way. There is no need to change the MC pressure to effect a change in braking force. Otherwise the big brake upgrade wouldn't work with stock MC.

Now, I'll admit there is a possibility that you're not changing the balance much, to where it really screws up the car. I'm just saying I did a front-only brake upgrade to a '97 CV, and the results were very wrong. I also did not notice until a hard use situation on a car that did not have ABS to mask it.

Why do do you think Wilwood sells an adjustable proportioning valve? Why do race cars have elaborate dual-master cylinder setups with a balance bar? This is a real setup parameter on any car. My point is simply that it something to consider when messing with brakes, a key safety and handling system in the car.

And if you've been driving around a car with ABS and increased front brakes, I'm going to say the ABS helped you not notice it. I don't know Mustangs, but back then the MC usually contained the PV, so you could have had somewhat correct results because you swapped the MC and PV.

Disable the ABS and hit the brakes hard. You think those beefy new fronts aren't going to lock prematurely? Just from your experience hotrodding cars, this should be apparent.

[lifespeed]

The only way to know if your brake proportioning is correct is to disable the ABS, and make a few test runs while having an observer note the wheel locking behavior of the car (although if you're good, you can feel which end of the car is locking up).

Just driving around with ABS turned on, not driving the car at full racing limits, and saying "I never noticed a problem" is not really an objective assesment.

The ABS does not control brake bias in an adjustable manner. It is a hydraulic valve fixed from the factory, to match factory brakes. When you're wheels aren't locking, what input signal would a (hypothetical) electronic brake bias valve act on? The front/rear fluid pressure ratio is controlled hydraulically under all braking pressures, not just lockup.

Look, I'm not trying to be a jerk or a know it all. I just went throught this with my last car a few years back, and am now looking to fix up the brakes on my Marauder. The best thing to do, when possible, is learn from others mistakes. Saves time and money.

[lifespeed]

The whole point of the proportioning valve is to prevent lock up.

That is nearly correct.

The point of the proportioning valve is to balance the force so that lockup occurs nearly simultaneous at the front and the rear (ideally you want front to lock up a hair before rear so you're less likely to swap ends) for a given vehicle setup. Suspension, F/R weight distribution, tire size, etc all play a role. As does brake configuration.

[lifespeed]

Here, just read this link (http://www.stoptech.com/tech_info/wp_proportioning_valves.shtml) if you're interested. Better than me trying to explain it.

[lifespeed]

Got a Marauder service manual on the way. I'll look at the schematic for the ABS and post any info regarding the extent of electronic control and PV configuration.

[RR|Suki]

Here, just read this link (http://www.stoptech.com/tech_info/wp_proportioning_valves.shtml) if you're interested. Better than me trying to explain it.

From your own link


Based on information gathered from the four ABS wheel speed sensors, the Dynamic Rear Proportioning (DRP) or Electronic Brake force Distribution (EBD) algorithms calculate the front-to-rear slip ratio of the four tires. Then, given preset thresholds and parameters, the ABS hardware can intervene and modify the brake pressure going to the rear wheels automatically.

Because DRP and EBD are based on actual wheel slip and not on brake line pressure, this type of rear proportioning is more flexible and adaptable to modifications one might make to their vehicle. It is also less expensive, as the OEM can now remove the mechanical proportioning valve from the vehicle and replace its function with other hardware already on board.

Whether or not ours is like that I don't know, but really you are really creating a problem where there isn't one. If it was a problem, the ABS would always have to be working hard on cars with big brake kits, that is just not the case.

[Todd TCE]

Assuming no other changes, a front only conversion will shift aprox 4% rear static rear brake bias into the Marauder. A very workable value given the vehicles wheelbase and rearward weight. For some wanting yet more front bias; a pad change to the fronts can easily bring static bias back to oe or beyond.

Often the purpose of the changes in the install of the big brake kit is to enhance the rear bias as well. A vehicle which nose dives hard under braking is generally a good sign of one that is poorly biased placing nearly all the brake demands on the front brakes. With smaller cars and short wheelbases this can prove the only way to enhance braking performance as just bout any change can elevate front bias and the rears are along for the ride. Luckily cars such as the Marauder have better balance characteristics for braking needs.

Changing a master won't have any effect on brake bias at all. Total pressure (assuming an equal bore mc, not split bore size) will remain the same relative to each end of the car; smaller bores producing more overall pressure but at the expense of pedal feel. Larger producing lower pressure but again equal to both ends.

The prop valve works in a manner to reduce output pressure based solely on input pressure: the more you put in, the less you get out. This is the cars dynamic bias. The point at which the pressure begins to reduce is known as the knee point. From here forward rear pressure drops preventing rear lock up. Back to the caliper changes we've elevated pressure needs a bit with the front only kit and as that pressure demand increases it self polices the rears again (perhaps at a different knee) as did the stock brakes.

If one were to execute to much of a shift in static bias trying to exploit to much rear brake the dynamic bias adjusted to reduce rear lock up my be exceeded. Then no matter what you'd find the rears wanting to lock up as the prop valve can only reduce so much pressure. How much is too much can be dependent upon wheelbase, weight distribution, tire choices, tire diameters, and of course road conditions. So why do mfgs offer such adjustable devices?? Well, so you can work around all those outside influences and set it to your needs. Adding one to a car with an oe system also is frowned upon as you're trying to reduce something that's already trying to be reduces and in a constant state of variable pressure.

ABS works to prevent wheel lock up as a safety device and shouldn't really be used as a biasing tool. If ABS kicks in under hard braking the first thing to consider is where? And then why? Turning on gravel may produce an ABS moment preventing the front tire from locking up as you're braking, whereas braking hard in the rain in a straight line may be the rear tires losing adhesion to the road. Not knowing where or why first makes diagnostics of how to change or prevent it difficult at best.

I don't know of any front kit that I sell personally that greatly elevates front or rear bias by any significant amount. That would be foolish. If you want to adjust it for your needs however the best means is by way of pad choice. You can swing bias by 6% or a bit more with a pad change alone. General rule of thumb: enlarge the rotor, reduce the piston area, tune with pad.





Based on information gathered from the four ABS wheel speed sensors, the Dynamic Rear Proportioning (DRP) or Electronic Brake force Distribution (EBD) algorithms calculate the front-to-rear slip ratio of the four tires. Then, given preset thresholds and parameters, the ABS hardware can intervene and modify the brake pressure going to the rear wheels automatically.


This being the case, as with most EBD systems however the computer doesn't know what brakes you're using or why. It's simply measuring the same values and making a correction to the fluid pressure to correct for it. If it could it would tap you on the shoulder and ask that you drag your feet less as you are upsetting the braking into the corner....It's taking input and defining output only.

[Got_1]

From your own link



Whether or not ours is like that I don't know, but really you are really creating a problem where there isn't one. If it was a problem, the ABS would always have to be working hard on cars with big brake kits, that is just not the case.

Exactly..........

[musclemerc]

Glad we have access to you on this site Todd. You are a wealth of knowlege. This is my favorite quote: You can swing bias by 6% or a bit more with a pad change alone. General rule of thumb: enlarge the rotor, reduce the piston area, tune with pad.

[Todd TCE]

Glad we have access to you on this site Todd. You are a wealth of knowlege


Certainly don't have all the answers but I've been doing this for some time now and learned a few things along the way. Always open to new ideas though.

[lifespeed]

Assuming no other changes, a front only conversion will shift aprox 4% rear static rear brake bias into the Marauder. A very workable value given the vehicles wheelbase and rearward weight. For some wanting yet more front bias; a pad change to the fronts can easily bring static bias back to oe or beyond.

Sounds like the total piston area remains the same, or even decreased slightly?

I suspect this was the source of the problem with the popular upgrade to '97 and earlier panthers using the '98 and later brake calipers and rotors. Many people did this. It was cheap, used factory parts, and greatly increased front brake power. However, the change was from a small single piston to a large twin piston caliper. And 12" vs 10.5" rotors to boot. Predictably, a huge brake imbalance problem was created. Many, many people did this with no change to the proportioning valve. A safety nightmare.


If one were to execute to much of a shift in static bias trying to exploit to much rear brake the dynamic bias adjusted to reduce rear lock up my be exceeded. Then no matter what you'd find the rears wanting to lock up as the prop valve can only reduce so much pressure. How much is too much can be dependent upon wheelbase, weight distribution, tire choices, tire diameters, and of course road conditions. So why do mfgs offer such adjustable devices?? Well, so you can work around all those outside influences and set it to your needs. Adding one to a car with an oe system also is frowned upon as you're trying to reduce something that's already trying to be reduces and in a constant state of variable pressure.

An adjustable PV, if needed, is a replacement for the factory part. Of course it should never be used in series with the factory valve.


ABS works to prevent wheel lock up as a safety device and shouldn't really be used as a biasing tool. If ABS kicks in under hard braking the first thing to consider is where? And then why?

Agreed. ABS is a great safety mechanism, but has nothing to do with brake balance. In fact, if one is attempting to judge the results of a brake modification and tune accordingly, the ABS should be disabled for the tuning session so it won't interfere with the evaluation process.

[Todd TCE]

Sounds like the total piston area remains the same, or even decreased slightly?

I suspect this was the source of the problem with the popular upgrade to '97 and earlier panthers using the '98 and later brake calipers and rotors. Many people did this. It was cheap, used factory parts, and greatly increased front brake power. However, the change was from a small single piston to a large twin piston caliper. And 12" vs 10.5" rotors to boot. Predictably, a huge brake imbalance problem was created. Many, many people did this with no change to the proportioning valve. A safety nightmare.



An adjustable PV, if needed, is a replacement for the factory part. Of course it should never be used in series with the factory valve.



Agreed. ABS is a great safety mechanism, but has nothing to do with brake balance. In fact, if one is attempting to judge the results of a brake modification and tune accordingly, the ABS should be disabled for the tuning session so it won't interfere with the evaluation process.



Well said on all accounts.

[2vmodular]

all the 2003-2004 mercury marauders have electronic brake force distribution (EBD). so no proporitioning valves are used in these cars anymore.

controlling brake force distribution through software allows for better optimized braking through a wider range of conditions than a mechanical proportioning valve could ever provide.

one bad thing about EBD is that when your antilock brake controller develops problems and goes into failsafe mode, full brake pressure is applied to the rear brake calipers. this can make for really dangerous handling characteristics during hard panic stops. here's a thread that i posted about this topic:

http://www.crownvic.net/ubbthreads/ubbthreads.php?ubb=showflat&Number=2083040

[2vmodular]

the antilock brake system has everything to do with brake bias in the 2003-2004 marauders. if you pull the abs fuses to disable the system, you'll have full line pressure always applied to the rear brake calipers. this is definetly not a good thing during a hard panic stop.

these cars use a bosch 5.3 abs controller, and unfortunelty no one seems to have figured out how to modify the programming tables inside to alter the brake bias. so you're stuck with the programming that ford installed. and unless you want to rip apart the hydraulic brake system in your car, remove the abs controller, and install a mechanical proportioning valve then you won't be altering the brake bias.


ABS is a great safety mechanism, but has nothing to do with brake balance. In fact, if one is attempting to judge the results of a brake modification and tune accordingly, the ABS should be disabled for the tuning session so it won't interfere with the evaluation process.

[2vmodular]

be warned that the people who wrote the ford service manuals didn't appear to talk with the production engineers that installed braking components into the car. electronic brake force distribution was mentioned in the crownvic service manual a couple years before these cars actually got the feature installed.


Got a Marauder service manual on the way. I'll look at the schematic for the ABS and post any info regarding the extent of electronic control and PV configuration.

[lifespeed]

these cars use a bosch 5.3 abs controller, and unfortunelty no one seems to have figured out how to modify the programming tables inside to alter the brake bias. so you're stuck with the programming that ford installed. and unless you want to rip apart the hydraulic brake system in your car, remove the abs controller, and install a mechanical proportioning valve then you won't be altering the brake bias.

Do you know if the proportioning is accomplished as a pre-programmed curve reducing rear pressure as a function of front (input) pressure similar to a mechanical valve, only using the ABS control hardware?

Or is the dynamic watch-for-wheel-slippage technique used?

[ik04]

I have a KVR 14" brake kit on my car and OEM size slotted rotors on the rear.

The brake force is really not noticeable except that the pedal pressure to stop the card is higher. The composition of the pads is a huge factor in how "grabby" the brakes are. My brakes are getting old and the ceramic pads are getting really hard and require more pedal pressure than when they were new.

Really hard braking, like after a 1320, requires a very heavy pedal force. The big brakes work best when pushed hard and will do it all day long with no fading. I do feel a slight shift in braking force to the front, but there is no antilock input that is different from the stock setup.

When I get new pads, I'll pay attention to the pedal force required and see if the balance feels different...