[92CXyD]

I use a 15/16" from a 91' EX sedan in my '92 CX with stock booster, no fitment problems.

Will be testing after I finish making new hard lines for the prop valve relocation.

 

[Full_Tilt]

Does that keep the hardlines in the same place or do you have to bend them around?

 

[xotic_crx]

So does anyone know what the number mean? Always wondered and finally got a 4040 since my fronts lock long before my rears on stock 90 So prop valve.

I don't think booster size plays a difference other than just feel. You can still stop the car as hard and balance isn't impacted. I ran no booster after mine blew and the car drove the same I just had to change how hard I pushed the pedal. I think MC will be the same, just feel and overall power, not balance.

 

[92CXyD]

Does that keep the hardlines in the same place or do you have to bend them around?

Just about all of my hard lines are getting made, I have all the tools to do it.

 

[92CXyD]

So does anyone know what the number mean? Always wondered and finally got a 4040 since my fronts lock long before my rears on stock 90 So prop valve.

I don't think booster size plays a difference other than just feel. You can still stop the car as hard and balance isn't impacted. I ran no booster after mine blew and the car drove the same I just had to change how hard I pushed the pedal. I think MC will be the same, just feel and overall power, not balance.

If you upgrade the braking system, to larger piston or dual piston caliper and convert rear disc brakes, it is a good idea to go with 15/16" master cylinder.

My brake setup:
2pot Legend GS calipers (reman)
Si size EBC slot rotors on cx/dx spindels
ebc yellow stuff pads
Sacrebird conversion rear disc conversion
RSX std rear calipers
Mini Cooper non-S EBC slotted rotors
EBC yellow stuff pads

'91 EX Sedan 15/6" Mastercylinder w/ stock booster
relocated 30/30 Prop valve.
New braided steel flex lines w/ black covers
All new hand bend hard lines with double flares and blue colored nuts.

All fits w/ my 14" HX rims.

Almost done with the lines, then everything gets mounted adjusted then remounted, probably take all weekend.

 

[JoelEspinoza]

I don't think booster size plays a difference other than just feel. You can still stop the car as hard and balance isn't impacted. I ran no booster after mine blew and the car drove the same I just had to change how hard I pushed the pedal. I think MC will be the same, just feel and overall power, not balance.

http://www.d-series.org/forums/general-tech/212594-crx-brake-boost-delete-stock-master-cylinder.html

I love my 13/16 MC and booster delete, I have never had a better feeling or reacting brake pedal. It also makes it much easier to run a hydro clutch in EFs.

 

[Chrisfrom1986]

Does that keep the hardlines in the same place or do you have to bend them around?

The hardlines don't need to be bent at all if you use a 15/16ths m/c from a 90/91 ex civic sedan, rs (non abs) dc Integra or da Integra.

 

[xotic_crx]

If you upgrade the braking system, to larger piston or dual piston caliper and convert rear disc brakes, it is a good idea to go with 15/16" master cylinder.

My brake setup:
2pot Legend GS calipers (reman)
Si size EBC slot rotors on cx/dx spindels
ebc yellow stuff pads
Sacrebird conversion rear disc conversion
RSX std rear calipers
Mini Cooper non-S EBC slotted rotors
EBC yellow stuff pads

'91 EX Sedan 15/6" Mastercylinder w/ stock booster
relocated 30/30 Prop valve.
New braided steel flex lines w/ black covers
All new hand bend hard lines with double flares and blue colored nuts.

All fits w/ my 14" HX rims.

Almost done with the lines, then everything gets mounted adjusted then remounted, probably take all weekend.

Not saying it's a bad idea, just saying it shouldn't effect balance. I switched to 10.3" fronts and DA calipers and ran with stock master for a while, only upgraded when I found an EX in the wrecking yard...which went bad so I bought a new 15/16 Prelude unit lol.

That said, why not switch to 15" wheels and good tires? If you're on anything short of a high performance summer tire you're over-braked for the tire.

http://www.d-series.org/forums/general-tech/212594-crx-brake-boost-delete-stock-master-cylinder.html

I love my 13/16 MC and booster delete, I have never had a better feeling or reacting brake pedal. It also makes it much easier to run a hydro clutch in EFs.

I got so used to it I preferred it. I mostly put it back for my new co-driver that joined me this season. It's much easier on street tires IMHO, but on R comps I felt adding the booster helped because the braking threshold was so much higher.

 

[92CXyD]

Not saying it's a bad idea, just saying it shouldn't effect balance. I switched to 10.3" fronts and DA calipers and ran with stock master for a while, only upgraded when I found an EX in the wrecking yard...which went bad so I bought a new 15/16 Prelude unit lol.

That said, why not switch to 15" wheels and good tires? If you're on anything short of a high performance summer tire you're over-braked for the tire.



I got so used to it I preferred it. I mostly put it back for my new co-driver that joined me this season. It's much easier on street tires IMHO, but on R comps I felt adding the booster helped because the braking threshold was so much higher.

I normally drive with Azenis RT-615k and they grip good for summer, and park in winter.

Looking for 15s soon I already have 2.5 sets of 225 or 245 wide road race slicks Hoosiers can not remember if they are R7 or A6s, got them from a guy is sponsored by Hoosier and they have up 3 heat cycles in them.

 

[JoelEspinoza]

I got so used to it I preferred it. I mostly put it back for my new co-driver that joined me this season. It's much easier on street tires IMHO, but on R comps I felt adding the booster helped because the braking threshold was so much higher.

Did you just remove the booster line? Or actually remove the booster? One of my CRXs has a 13/16" with no booster, and the other has a 7/8 with an HF booster and they are pretty close to the same pedal pressure, the one with the booster has a LOT more play though.

 

[xotic_crx]

I normally drive with Azenis RT-615k and they grip good for summer, and park in winter.

Looking for 15s soon I already have 2.5 sets of 225 or 245 wide road race slicks Hoosiers can not remember if they are R7 or A6s, got them from a guy is sponsored by Hoosier and they have up 3 heat cycles in them.

Stagger that stuff if you're making some power, more tire up front. You probably won't get the rears up to temp even with a 225 at autox, especially if they're R's and not A's.

Did you just remove the booster line? Or actually remove the booster? One of my CRXs has a 13/16" with no booster, and the other has a 7/8 with an HF booster and they are pretty close to the same pedal pressure, the one with the booster has a LOT more play though.

I just unhooked the line since the diaphragm failed. No play in the pedal. New car is an HF so I'm excited to see how it feels.

 

[Mr.Fodo]

So does anyone know what the number mean? Always wondered and finally got a 4040 since my fronts lock long before my rears on stock 90 So prop valve.

I don't think booster size plays a difference other than just feel. You can still stop the car as hard and balance isn't impacted. I ran no booster after mine blew and the car drove the same I just had to change how hard I pushed the pedal. I think MC will be the same, just feel and overall power, not balance.

The way I see it:
Booster = Pedal feeling of pressure
Master = Brake threshold point
Prop = Balance

But the idea is #'s are related to spring pressure of prop valve most likely. So IMO the line pressure out on a 30/30 is equal to line pressure out for 40/40 if all brakes are stopping equally (straight line).

But if the car is braking say while turning (where one tire has more traction or resistance from stopping-- think of one tire completely locked up and the other not) or something, the 30/30 would be more/less sensitive to differences in pressure from one side to the other than the 40/40 which has higher spring rates. I mean the prop valve is just a pressure relief valve really.

So a higher spring rate, like suspensinn, would transfer more of the "jarring/jerking/uneven-ness" where the softer one is more forgiving. But these difference are probably minimal to the average joe. Which makes the whole prop valve thing messy.

 

[Full_Tilt]

^ Yet again, I dont think the "4040" or "3030" actually have anything to do with proportioning. Or at least I havent seen any evidence one that the numbers mean anything. They may only be some kind of part number.

Other than in the honda world, I have never heard of proportioning valves being referred to as any kind of ratio. Plus, most of these ratios make no sense. A 30/30 or 40/40, wouldnt that just be equal pressure front and back, with the 40 allowing for a higher maximum pressure perhaps?
My understanding of a proportioning valve is basically that it tries to limit the pressure going to the rear brakes. So the as the pedal is depressed the pressure rises together freely, then at a certain pressure the rear brake pressure starts to taper off while the front pressure increases. This is setup so ideally the front brakes will lock up just before the rears do.

On the old racecars we would use a "bias-bar" brake setup that had 2 master cylinders, one for front, one for rear, and a linkage like this to distribute braking force proportionally.

With this setup, the graph should be linear, where the slope is adjusted by adjusting the linkage. So you actually are dividing up the brake force and could give it some kind of ratio like 60/40, or 70/30.

 

[Mr.Fodo]

Yea it was a late night drunk rant thing. But I mean ideally it should indicate a difference. And that would be the only thing that comes to mind for me at least.

The other thing is the 6th gen prop valve looks like one solid unit, so maybe they use a different method.

The setup you posted is ideal because you can literally calculate the bias easier. The bias will also be more consistent. The whole spring thing or whatever setup in the 5th gen adjusts the pressure to the rear more dynamic. Which is why you hear the weird talks about rear locks and then "sends" the pressure back to the front before the rear locks up again (at least I've read that more than once).

From what I gather they are describing the feeling of the spring oscillating to steady state (no damper so).

Biggie and I have dissembled the unit before and I think I remember a spring falling out but I couldn't find any pics of it online immediately.

The random diagrams I have found show a spring between the front and rear though. But they don't seem be Honda specific ones either...

 

[Mr.Fodo]

Just to bring it home, I think it's like this:

The 30/30 and 40/40 are the same like you say. But it's the tiny difference of what happens between initial braking to final steady state that makes it different. Point A and point B are the same but the "area under the curve" is a tad different.

But the 30/40 fucks with my logic still. Which is why I didn't talk about it lol.

Maybe one number is the "bias" and the other is the bleeder value. People have leaked from the rubber plug.

 

[JoelEspinoza]

What if the 2 numbers dont refer to the same thing? Instead of being front/rear pressure, they could be rear volume + pressure, or rear pressure + timing delay of some sort.

If they are real measurements and not just random part numbers, the back brakes recieving 30% of the pressure and 30% of the volume isnt unrealistic.

I just unhooked the line since the diaphragm failed. No play in the pedal. New car is an HF so I'm excited to see how it feels.

If you get bored some day and have an extra booster laying around to sacrifice, you should give what I did a try. I have driven for years with an unhooked booster, but the actual removal is a lot nicer, and lowers the effort quite a bit.

 

[Mr.Fodo]

That could be it too. But maybe opposite even. Since the 40/40 is suppose to help the rear not lock up first right?

So maybe 40% less pressure from the front and 40% less volume.

Now that I think of it. We could do a simple test with spare prop valves, brake masters and lines. And literally measure the difference in fluid amounts... I just don't have a spare 30/30 laying around.

 

[xotic_crx]

Fodo, I'm in for this. What did the 3030 come from again?

 

[AutoXCivic]

I like where this is going. Subscribing to watch actual sciencing taking place. I can run to the local pick and pull if between everyone on the forum we don't have enough spare parts lying around.

 

[JoelEspinoza]

I just unhooked the line since the diaphragm failed. No play in the pedal. New car is an HF so I'm excited to see how it feels.

I missed this before.

Yea, the pedal doesnt feel like it has any play with just an unhooked booster, but then when you feel it back to back after a booster removal it is a night and day difference.

Ive driven hondas for 10 years with the boosters unhooked and they felt great, then I removed the booster and realized they could have been amazing.