Brake booster/MC Setups -testing and results

[BEXE]

Thought I would share some Extensive Testing and results that a super anal friend of mine performed.

And when I say anal I mean like stripped every bolt, braket, pin, etc. From his Subaru project and had them all cadmium plated, then organized them by thread and size to store them for the rebuild. It's to the point at times he's a bit of a douche...

That being said know that this research was done in search of the best overall pedal feel, Performance, and overall system abilities.

The brake boosters tested with were the manual single bubble, and auto/z32 double bubble boosters. Each were used with each MC listed.

The MC list were the
-manual 240
-auto 240
-z32 1"
-z32 1 1/16"

The brake setup is the larger z32 setup front and rear with SS lines and hp pads.

THe single bubble booster with manual MC
-very stiff pedal
-easy to lock fronts with little travel

SB and Auto
-A better overall pedal travel
- still easy to lock the fronts

SB and 1"
- a little too much pedal travel
- fronts are a bit of effort to lock

SB and 1 1/16"
- to much pedal travel
- front lock is with great effort

The DB booster exacerbated the results of each ending with the s14 auto BMC having the best travel and locking distance/effort. It really made his csr a joy to drive and is very predictable even when the brakes fade.

Hope this is helpful

-Dave

[hai1206vn]

What pads did he use? HPS or HP+?

[BEXE]

Hp+ at first, he didnt like the noise, so he went with If I remember correctly some style of project Mu

[cdlong]

That doesn't make any sense, the smaller MCs should have longer travel. You should have a stiff pedal with the 1 1/16 MC and a long pedal with the manual MC.

[BEXE]

I understand where you are coming from, but there is a finite amount of fluid in yOur braking system, the amount of fluid needed to move your brakes is a defined by the size and number of pistons in the system and the size/diameter/length of the lines and material. That being said, with a properly bled brake system (I.e. Near 0 loss in force Hydraulics basics), the smaller BMC will move all of it's fluid out faster than the larger BMC due to the piston length only being so long in the BMC and your pedal travels pivot point setting the fulcrum distance, and power increase of your for force you apply.

Sorry if I am not the best at explaining it, I have been out of school for a while and my career field mainly deals with electronics nowadays; when I was learning about hydraulics I learned that like a turbo system bigger is definitely not better; sized to your systems abilities/expectations is always best.

[cdlong]

Ahh, that's probably booster runout you're running into. The booster only has so much range and will stop providing assistance and the pedal gets incredibly stiff. There should still be travel left in the MC after that to provide some braking force. Once the MC bottoms out, that's it, you won't get any more braking. Thought there would have to be a range of travel where everything is working together before you hit booster runout. blowing through that too quickly is actually exacerbated by air in the lines. The fact that everything is still linear (small MC=short travel, large MC=long travel) makes me still think your notes are wrong. I have z32 brakes, auto s14 booster, and 1 1/16 MC, the pedal is stiff with very little travel.

The z32 booster and auto s14 booster aren't equivilant BTW. The z32 is larger diameter.

[BEXE]

Gotcha, it was my understanding that double bubble was double bubble in booster terms. The booster runout must take up for a bit of it, but at speed it shouldn't have as much of an effect; the lines were bled properly with no air.

Does anyone else have experience they want to share, or thoughts on the matter?

[Tower240sx]

your results are backwards, sorry

if a 1 1/16" piston travels further (as stated) in the same system as a stock (1") then you have fluid disappearing or air in your system,

this is not up for discussion, that is how that works.

please revise your results, retest or rebleed, this info is simply wrong

swept volume closed system, end of story

[Def]

Sounds like lots of air in the lines. A 1" MC with a manual S13 booster gives a SUPER stiff pedal if you actually bleed the brakes properly. I'd say 70% of the cars I've felt in person with a 17/16" MC had air in the lines.

[BEXE]

So you are saying that the system should be best with the 17/16th BMC? I currently have the s14 manual booster and BMC in my car now; and the pedal is pretty rock solid, and with only a little pedal travel the fronts lock up (first), then the rears with nominal force applied. I understand this is the smallest BMC available, but your examples it should have the greatest pedal travel from initial to locked?

[cdlong]

Not necessarily best, but certainly shortest travel with the 17/16ths MC. I assume we're still talking about the z32 front and s14 rear calipers? How much pedal effort is involved?

[Matt93SE]

also, when were the pads changed? you mentioned the guy changed pad compounds sometime. unless the entire procedure was restarted from the beginning, then the results are invalid. Changing the pad material changes the way the entire brake system feels and operates.

i.e. Ferodo DS2500 pads are slightly compressible. didn't matter how well I bled the system, I ALWAYS had a soft pedal with them. I pulled them out and dropped in a set of Hawk HT-10, which are a much harder material (not necessarily better, but it doesn't compress. think metal vs. rubber inside your caliper). I didn't bleed the brakes or change rotors between pad changes, just the pads only. the pedal went from mildly mushy to hard as a rock.

also, you have to change both front and rear pads to really be able to talk about bias and handling issues when you move this stuff around.

[BEXE]

They are z32 brakes F/R. There is moderate pedal travel involved. He switched to the project Mu's in the start. What MC's has everyone ran with this setup; and what are your experiences? I have a 17/16ths in the garage bnib and a s14 auto with auto booster. I have driven his car on all of the setups; each had a different pedal sweep. The longest pedal sweep (greatest range of modulation) was the z32 17/16ths BMC, the manual S14 BMC was the shortest range of motion from none to full lock.

[BEXE]

So i've crunched the numbers and I'm just a dumbass: sorry everyone. The only good explication is air in the lines.

[croustibat]

i got a 17/16" on my S13, and managed to lock the wheels at around 100mph (wilwood superlite + polymatrix pads front and 330x32 brake discs, Z32 rear with project mu pads). And yes, the road was dry...

So yes, it can lock wheels pretty easily, as long as you apply force on it. Short travel too ... i sometimes wish i put the 1" in there to get a little bit more travel and precision.

[Beejis60]

i got a 17/16" on my S13, and managed to lock the wheels at around 100mph (wilwood superlite + polymatrix pads front and 330x32 brake discs, Z32 rear with project mu pads). And yes, the road was dry...

So yes, it can lock wheels pretty easily, as long as you apply force on it. Short travel too ... i sometimes wish i put the 1" in there to get a little bit more travel and precision.

What booster do you have? And why were you attempting to lock at 100mph?!!??

[Matt93SE]

I've inadvertently locked mine at 120 before. Not hard when you're trying to outbrake someone, but its not like I try on the street.

[Beejis60]

Makes sense

[CodyAce]

15/16 Z31
Def/Wilwood setup, Carbotech Xp12 up front
Altima Rotor/S14 Caliper/ Carbotech Xp12 out bac

works fantastic to me. Will lock them in a panic situation, or in a cool guy one.

[croustibat]

What booster do you have? And why were you attempting to lock at 100mph?!!??

OEM S13 ca18det manual gearbox booster.
i got Z32 brakes rear with project mu pads, and 330x32 discs front with wilwood superlite calipers and polymatrix pads.

I was NOT trying to lock, just trying to avoid some retard that thought it was the best time and place to overtake someone, without looking in its mirror.. I recovered and avoided him so no damage, but that was quite surprising. I did not think it could lock at that kind of speed tbh.

[Beejis60]

OEM S13 ca18det manual gearbox booster.
i got Z32 brakes rear with project mu pads, and 330x32 discs front with wilwood superlite calipers and polymatrix pads.

I have read that the 17/16" MC is a bit too stiff for some users with the BB from an MT vehicle; seems most like the 1" with the MT BB or 17/16" with the AT BB. I personally prefer the stiff pedal.

I was NOT trying to lock, just trying to avoid some retard that thought it was the best time and place to overtake someone, without looking in its mirror.. I recovered and avoided him so no damage, but that was quite surprising. I did not think it could lock at that kind of speed tbh.

Ya, retards exist... gotta be aware. At least you avoided an accident.

[konjiki7]

Stupid question is there a difference between abs ms and non abs or?

I had an abs ms and it was replace with a non abs and the car doesn't seem to lock at all.

I'm wondering if the reman unit is bad or there just a difference in performance.

[BEXE]

ABS and non- ABS have different BMC's the ABS's are 1 inch with a single front and a single rear output. The Non-abs come in auto which is slightly larger than the manual BMC.