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Brake Proportioning Valve

on the majority of cars that do have them, they are siezed up anyway, so it's no big deal not to have one.
 
LOL ok mate ;)

On all cars I have in, when they are seized, they need to be un-seized so that the car handles decently let alone safely....This is especially so if the car is stripped out (or if it has a heavier engine up front, or has better brakes)

Its a pretty simple principal really....
 
on the majority of cars that do have them, they are siezed up anyway, so it's no big deal not to have one.

And that'll be why they'll fail MOT then. (See ChrisH's tech thread on them and why they're needed cos you don't seem to believe us)
 
I dont really care what he or anybody else says, tbh, if its contradicting that a brake bias valve isnt going to be necessary on a car with a heavier engine upfront, and with 4pot calipers, then they are wrong to put it bluntly.
 
I can't be bothered to argue cos you obviously know best just because your car doesn't have one therefore no-one elses needs one.
 
look child....the point you are missing here is this, the bias valve you are refering to is a load sensitive valve, that is affected by weight in the rear of the car, if it doesn't have one, it doesn't need one, as this is metered by the master cylinder, so only if the full braking system is being transfered from a vehicle that had one fitted, is one required.


Have a read.


To reduce hydraulic pressure to the rear brakes so the rear brakes don't lock up when the brakes are applied, a "proportioning valve" is required. This valve helps compensate for the differences in weight distribution front-to-rear as well as the forward weight shift that occurs when the brakes are applied.

What we're really talking about here is "brake balance" or "brake bias," which is the difference in the amount of hydraulic pressure channeled to the front and rear brakes. The front brakes on most RWD vehicles normally handle about 60- to 70 percent of the brake load. But on FWD cars and minivans as well as RWD and 4WD pickups and SUVs, the percentage handled by the front brakes can be as much as 90 percent of the load. Consequently, the front brakes need a higher percentage of the total hydraulic force that's applied to keep all four brakes properly balanced.

If the front-to-rear brake force isn't balanced correctly by the proportioning valve, the rear brakes will receive too much brake force causing them to lock up and skid when the brakes are applied.

The other reason for using a proportioning valve to reduce hydraulic pressure to the rear brakes has to do with the design of the brakes themselves. When hydraulic pressure is applied to the wheel cylinder inside a drum brake, the shoes are pushed outward against the drum. When the shoes make contact, the rotation of the drum tries to drag them along. But since the shoes are anchored in place, the drum only pulls the shoes up tighter against itself. Because of this, drum brakes that are "self-energizing" require little additional pedal effort once applied.

Disc brakes, on the other hand, are not self-energizing. It takes increased pedal effort to squeeze the pads against the rotor. In a vehicle that has front disc brakes, and drums in the rear, the drums generate increasingly greater amounts of friction with little additional pedal effort while the discs require increased effort just to maintain the same amount of friction. So the proportioning valve splits the applied pressure so each brake receives just the right amount.

Inside the proportioning valve is a spring-loaded piston that determines how much pressure goes fore and aft. Each valve is calibrated for a specific application by the vehicle manufacturer, so it's important to make sure you get the correct replacement valve for a customer's vehicle if the original valve is defective. The calibration of the proportioning valve is fixed and cannot be adjusted.

Some vehicles have "load sensing" proportioning valves that change rear brake metering to compensate for changes in vehicle loading and weight shifts that occur during braking. This type of proportioning valve has an adjustable linkage that connects to the rear suspension or axle. As the vehicle is loaded, ride height decreases and pressure to the rear brakes is increased. This type of proportioning valve can be found on many minivans, pickups and even some passenger cars (Ford Tempo or Mercury Topaz, and Ford Taurus or Mercury Sable to name a few).

Load sensing proportioning valves are adjustable, and must be adjusted correctly if they are to properly balance the rear brakes to the vehicle's load. The valve linkage is adjusted with the suspension at its normal height (wheels on the ground) and the vehicle unloaded. The adjustment bracket or linkage is then adjusted according to the vehicle manufacturer's instructions, which typically involves adjusting the linkage to a certain position or height.

Load sensing proportioning valves are also calibrated to work with stock springs. Any suspension modifications that increase the load carrying capability (installing helper springs, overload or air-assist shocks for example) may adversely affect the operation of this type of proportioning valve. Modifications that make the suspension stiffer reduce the amount of deflection in the suspension when the vehicle is loaded, which prevents the proportioning valve from increasing rear brake effort as much as it normally would.

A defective proportioning valve or one that is not adjusted properly can also upset brake balance. So if the rear brakes on a vehicle seem to be overly aggressive (too much pressure to the rear brakes), or the vehicle seems to take too long to stop (not enough pressure to the rear brakes), the problem may be a bad proportioning valve. Proportioning valves can be tested by installing a pair of hydraulic gauges (one on each side of the valve) to see if the valve reduces pressure as it should.

On some newer vehicles, the mechanical proportioning valve has been replaced by "electronic" brake proportioning which is controlled through the ABS system. By sensing wheel speeds, the ABS system reduces pressure to the rear brakes as needed to keep them in proper balance with the front brakes.
 
Copy and paste overtime... and please, don't call me a child as i'm far from a child!

Right so i've read that and i'm still not seeing your point... which part of that say's that Bens car doesn't need a "Proportioning" or "Bias Valve"? It doesn't because infact it says that he should have one.

If the front-to-rear brake force isn't balanced correctly by the proportioning valve, the rear brakes will receive too much brake force causing them to lock up and skid when the brakes are applied.

The other reason for using a proportioning valve to reduce hydraulic pressure to the rear brakes has to do with the design of the brakes themselves. When hydraulic pressure is applied to the wheel cylinder inside a drum brake, the shoes are pushed outward against the drum. When the shoes make contact, the rotation of the drum tries to drag them along. But since the shoes are anchored in place, the drum only pulls the shoes up tighter against itself. Because of this, drum brakes that are "self-energizing" require little additional pedal effort once applied.

Disc brakes, on the other hand, are not self-energizing. It takes increased pedal effort to squeeze the pads against the rotor. In a vehicle that has front disc brakes, and drums in the rear, the drums generate increasingly greater amounts of friction with little additional pedal effort while the discs require increased effort just to maintain the same amount of friction. So the proportioning valve splits the applied pressure so each brake receives just the right amount.

Inside the proportioning valve is a spring-loaded piston that determines how much pressure goes fore and aft. Each valve is calibrated for a specific application by the vehicle manufacturer, so it's important to make sure you get the correct replacement valve for a customer's vehicle if the original valve is defective. The calibration of the proportioning valve is fixed and cannot be adjusted.

Some vehicles have "load sensing" proportioning valves that change rear brake metering to compensate for changes in vehicle loading and weight shifts that occur during braking. This type of proportioning valve has an adjustable linkage that connects to the rear suspension or axle. As the vehicle is loaded, ride height decreases and pressure to the rear brakes is increased. This type of proportioning valve can be found on many minivans, pickups and even some passenger cars (Ford Tempo or Mercury Topaz, and Ford Taurus or Mercury Sable to name a few).

Load sensing proportioning valves are adjustable, and must be adjusted correctly if they are to properly balance the rear brakes to the vehicle's load. The valve linkage is adjusted with the suspension at its normal height (wheels on the ground) and the vehicle unloaded. The adjustment bracket or linkage is then adjusted according to the vehicle manufacturer's instructions, which typically involves adjusting the linkage to a certain position or height.

Load sensing proportioning valves are also calibrated to work with stock springs. Any suspension modifications that increase the load carrying capability (installing helper springs, overload or air-assist shocks for example) may adversely affect the operation of this type of proportioning valve. Modifications that make the suspension stiffer reduce the amount of deflection in the suspension when the vehicle is loaded, which prevents the proportioning valve from increasing rear brake effort as much as it normally would.

A defective proportioning valve or one that is not adjusted properly can also upset brake balance. So if the rear brakes on a vehicle seem to be overly aggressive (too much pressure to the rear brakes), or the vehicle seems to take too long to stop (not enough pressure to the rear brakes), the problem may be a bad proportioning valve. Proportioning valves can be tested by installing a pair of hydraulic gauges (one on each side of the valve) to see if the valve reduces pressure as it should.

I've already said on page 1 that just because you don't have one it doesn't mean Ben can get away without having one as your ABS system will sort you out as it does on the non-Cup 172's. Bens 19 doesn't have ABS but he's now running 4 pot callipers and rear discs on a master cylinder setup that's not designed for that specification nor does it have ABS so again, he needs the adjustable bias.
 
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who said any of uswere refering to an OE bias valve....i certainly wasnt. An OE type one would be a start, but if you read (and perhaps understand) what i was talking about earlier you'll see i was on about a bias-bar arrangment in the pedal box...i never mentioned the oe one.

regardless of whether it HAD one or not, it WILL now need one.
 
well youve just proven you dont really understand what im on about....

If, like I suggested, you were to have a pedal box, with a bias bar operating the master cylinders, the master cylinders ARE NOT self proportioning. They are designed for motorsport applications and as such DO NOT have an in built regulation feature....they are designed to be driver adjustable, so bias can be tweaked for optimum vehicle control.
 
so in which case he needs one that is a custom job, so Mick saying that he needs one from a 16v is bollox, as they are not adjustable they are pre set. And very rarely (if ever) would anyone want to adjust it anyway, even on rally cars they are rarely adjusted, around 90% of the braking on a FWD car is carried out by the front barkes, once it's set, unless he is going rallying on really bwndy stuff (which I doubt very much) once it is set, that is how it will stay.

And I'm presuming that he has a tapley meter available to him to set the bias?
 
so in which case he needs one that is a custom job, so Mick saying that he needs one from a 16v is bollox, as they are not adjustable they are pre set. And very rarely (if ever) would anyone want to adjust it anyway, even on rally cars they are rarely adjusted, around 90% of the braking on a FWD car is carried out by the front barkes, once it's set, unless he is going rallying on really bwndy stuff (which I doubt very much) once it is set, that is how it will stay.

And I'm presuming that he has a tapley meter available to him to set the bias?


are you really that thick??

YES...braking effort is split to the front, but the actual proportion of pedal force (as regulated by fluid pressure via a bias bar), is TOTALLY dependent on overall vehicle mass. The point here is vehicl mass is being altered, and it is being slkung over one end...the dynamics of the car will change, and this needs to be compensated. Whats more, he is fitting 4pots...so brake bias will need increasing to the front.

And how many driver DONT touch brake bias?? LMAO!!! have you ever done any track set-up with race cars....i suggest you go look up whats involved, son.
 
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