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Proportioning Valve and Brake Switch


Uber Deaf One

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My 510 has 280ZX front brakes and stock rear brakes... I'm trying to get more braking power to the rear brakes for Autocross. I understand the 510 doesn't have a proportioning valve... so if I were to get an adjustable proportioning valve, I could put it on the front brakes to limit pressure going to the front brakes, which means more braking to the rear, correct? If this is the case, would this mess with the brake switch light?

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brake light switch is just above the pedal, about an 8th inch in from you pushing it they pop on. as long as you dont move that switch, it shouldn't affect your brake lights period.

 

when you push the brake pedal down, the switch tip comes out causing it to ground and switches the lights on.

 

this one is for a honda, but same thing. its the white tip on the bottom of the picture. when you release your brakes it pushes that rod back in breaking the ground connection causing the lights to go off.

auto-part-brake-light-switch-for-opel.jpg

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My 510 has 280ZX front brakes and stock rear brakes... I'm trying to get more braking power to the rear brakes for Autocross. I understand the 510 doesn't have a proportioning valve... so if I were to get an adjustable proportioning valve, I could put it on the front brakes to limit pressure going to the front brakes, which means more braking to the rear, correct? If this is the case, would this mess with the brake switch light?

 

Hahahaha (sorry) for a moment there I thought you said to limit pressure going to your brakes, the biggest safety device on your vehicle. About 80% (if not a lot more) of your braking is done by the front brakes. They have the weight of the motor and transmission over them to increase traction and prevent them locking up. In addition, weight transfers forward when the brakes are applied adding even more front wheel traction. If you think about it again, you will see that anything that reduces your braking (front or backs) is simply wrong headed.

 

Are you still using the 510 master? If so get the proper 15/16" zx master for it. It will move much more fluid needed to work those bigger front calipers. It may over power the rears and cause early lock up. You may be able to turn the back off the rear adjusters to add some rear shoe travel to even it out.

 

 

Sorry I should have clarified, I'm talking about the light that comes on the dash when you're out of brake fluid. I was told the 510s have this...

 

EDIT: Pressure differential switch is what I'm asking about, not the brake light switch lol, sorry.

 

The 510s do not have a sensor in the master to detect low fluid. That wasn't used until the 80s. The pressure differential switch on a dual master system warns that pressure has been lost in one of the systems.

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First make sure your rear brakes are adjusted correctly. When I adjust mine it helped to keep the car level while braking. I am still able to lock up my front brakes.

 

 

Mike, on the 510's their is a yellow/green? (i think green is correct) wire that connects to the divider from the master. What is this monitoring?

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Hahahaha (sorry) for a moment there I thought you said to limit pressure going to your brakes, the biggest safety device on your vehicle. About 80% (if not a lot more) of your braking is done by the front brakes. They have the weight of the motor and transmission over them to increase traction and prevent them locking up. In addition, weight transfers forward when the brakes are applied adding even more front wheel traction. If you think about it again, you will see that anything that reduces your braking (front or backs) is simply wrong headed.

 

Are you still using the 510 master? If so get the proper 15/16" zx master for it. It will move much more fluid needed to work those bigger front calipers. It may over power the rears and cause early lock up. You may be able to turn the back off the rear adjusters to add some rear shoe travel to even it out.

 

 

 

 

The 510s do not have a sensor in the master to detect low fluid. That wasn't used until the 80s. The pressure differential switch on a dual master system warns that pressure has been lost in one of the systems.

 

 

First make sure your rear brakes are adjusted correctly. When I adjust mine it helped to keep the car level while braking. I am still able to lock up my front brakes.

 

 

Mike, on the 510's their is a yellow/green? (i think green is correct) wire that connects to the divider from the master. What is this monitoring?

 

 

there is a wire on the master. When you press the pedal to the floor it will light up your brake light. (on some it may be the parking brake light, but on my 69 it just says brake)

 

is that what he is talking about?

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Mike, actually there is a wire on the master. When you press the pedal to the floor it will light up your brake light. (on some it may be the parking brake light, but on my 69 it just says brake)

 

No wire connected to the master on mine, and it doesnt light of the brake light with a full peddle push (unless you can press the pedal to the floor?).

 

You can see what I am talking about here: its the thing with all the brakes lines...

IMG_5831.JPG

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edited

 

Well then im not sure, i was told that wire was for if you were out of fluid or there was an issue with your brakes it would light up. Thats the only wire connected (that i see) to the brake system that would be able to trigger the brake light switch.

 

It'd make more sense if that was what the wire was for, if it was on the master. But its not, so guess i am unsure.

 

Anyways.. Video/pic

 

2011-09-21_20-53-17_244.jpg

th_2011-09-21_20-55-25_190.jpg

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Mine is quite connected. Even in that picture. So does it just say you lost pressure when the light is on?

 

 

haha sorry, looked like it wasn't connected.

 

To your question, not sure bro. Ill pull the wire tomorrow night when i get home and see if it lights up still. If so, then guess i just had this wire all sorts of wrong.

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there is a wire on the master. When you press the pedal to the floor it will light up your brake light. (on some it may be the parking brake light, but on my 69 it just says brake)

 

is that what he is talking about?

 

Is it the stock master?

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Already running a 15/16" 280ZX master cylinder.

 

The car isn't even on the road yet, but we are getting ready to run all of the brakes lines so I'm trying to figure all of this out now so we don't have to redo things. So I shouldn't even bother with the proportioning valve?

 

Also my pressure differential switch looks fairly corroded... it actually looks a lot like the one in Laecaon's pic.. should I be worried? It hasn't had brake lines hooked up or anything in probably a year. Would it need to be rebuilt? Or just cleaned out?

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  • 2 years later...

so when running my ebrake cables, i noticed that my rear calipers were on the wrong sides so i switched them, not  hooked up to the brake lines i stepped on the pedal forgetting my calipers weren't hooked up.... so i threw the proportioning plunger all the way to the other side  and now when im bleeding the brakes when the pedal is all the way down the light pops up on dash, so im wondering if i have to reset the valve manually or it should eventually go back to center after another bleed ?

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It should self center. It registers a pressure differential between the front and back circuits. Once the low side comes back up it shuts off the lamp.

 

I've replaced front disc pads and had to push the caliper piston back inside to slide the new pads in. It took several pumps of the pedal to bring the piston back out against the backs of the pad. The light came on right away but went out on the third pump.

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Test booster...

 

Pump brakes to bleed any stored vacuum.

Step down on brake and hold.

Start engine.

The pedal should drop slightly as vacuum builds.... normal opperation

 

 

If engine stumbles when applying brake, the booster may be leaking. Pinch hose closed and try again.

If that fixes it then booster has a leak.

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tested seems to be fine its a very small drop though maybe 1/4 in. from what i can tell

 

now while doing this i noticed after the fifth pump the light does not come on and it feels like normal brake pressure ( both car on and off)  could this mean air still trapped somewhere?  

 

Bikuri !

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