STI Master Cyl. and Brake Booster SWAP SUMMARY for LGT

Just got my STI BB/MC and am doing this in conjunction with upgrading the outback brake system to LGT system. Really looking forward to the increased braking capacity. Thanks for the mod. Cheers!

Hate to burst everyone's bubble, but this mod isn't as great as advertised. I just got my OBXT back from Cobb Socal on Saturday. YES, there is a noticeable difference in pedal travel and pedal firmness, but it's hardly better.

 

As a quick refresher, I've installed LGT calipers, LGT Stoptech rotors, LGT Stoptech pads, SS lines, Motul fluid, Grimmspeed MC Brace, and now, the STI MC/BB. Short of a full Brembo swap, or race pads, I can't imagine this thing being better than it currently sits.

 

And it still isn't good enough.

 

Before the STI MC/BB swap, I was actually getting used to it (wife's car, I only drive on weekends).

 

Me, From 6/17:

 

I took my wife's OBXT to Cobb SoCal yesterday. They installed LGT calipers, LGT spec Stoptech rotors, LGT Stoptech pads, SS lines, and the GrimmSpeed MC brace.

 

I drove 80 miles on the OB today and the brakes still suck. To qualify my observation, allow me to say that I'm an automotive journalist and I drive 2-3 different cars every week, and I'm adept at picking out the subtle nuances in every vehicle.

 

The OB still has a long brake travel, the depression is still mushy, and there is no discernable increase in clamping power. That much is subjective, but even stomping on the brakes for a quick start--it still doesn't feel like it will stop quicker, or in a shorter distance than before.

 

*edit '05 OBXT 5AT, no VDC

 

and

 

The brake package that was installed included new oil. I did not watch the technicians bleed the system, but only one of the three bottles I bought from brakeswap.com came back to me. So, either they bled the system and added new oil, or they kept two bottles. I'm not that jaded to believe I got ripped off.

 

As for my own car, I drive a WRX Wagon with H6 rear brake upgrade, Goodridge lines, Axxis ultimate pads, and atb600 fluid. I'm happy with the travel, the sensitivity, and what I perceive as clamp/lockup when I depress the pedal quickly.

 

and on 7/20, in my photo/profile thread:

 

At the moment, I am waiting on the vacuum hose for the STI Master Cylinder and Brake Booster install. I ordered it a week ago (from this posting) and it seems to be out of stock in Socal. Thanks to Craig, btw, for the details and info related to this install. Hoping for install on August 4, or August 11.

 

In the meantime, allow me to share what the OBXT is like with LGT calipers, LGT Stoptech rotors and pads, SS lines, and Grimmspeed MC brace:

 

For the first week, I felt almost no difference. This is surprising to me, as I really felt the SS lines and GS MC Brace would have done something positive for the pedal feel and brake performance. As I've mentioned in the brake thread, I am an automotive journalist. I drive 2-3 different brand new cars every week. That said, the OBXT has the worst brake FEEL of any car I have ever driven. Statistically, I don't know if it is the worst PERFORMING brake system I've driven, but reports from 2005 indicate a stopping distance of about 160-165 feet from 60 mph.

 

That is unacceptable under every circumstance in my book.

 

This is my wife's car and it is driven city mileage almost exclusively. It will not see a track, despite the hardcore suspension. That is simply how my wife wanted her car to look and drive around town. Yes, she's awesome. The OB is also our family car, since it has a lot more space than my WRX wagon. So, that means it is our road trip vehicle when I'm not driving a new car from work. As much as I'd like to have more power, the tires, brakes, and suspension are more important and practical safety considerations than big time power, hence why we went this route first.

 

Now that the OB has 500+ miles since the brake install, allow me to reconsider some of my earlier thoughts:

 

There is a slight difference compared to the first few miles. Although I am an auto journo, I don't know a lot about brakes to accurately reflect what it is I feel. Also, I only drive the OBXT on the weekends, coming from my own WRX.

 

I feel more friction in clamping power when I step on the brakes. With a casual slowing down to stop at a light, the brake pedal is still mushy and it doesn't begin to clamp until halfway down on the pedal. AFTER the mush is where I feel the increased "friction" in the clamp.

 

When stopping quickly, or suddenly, with hurried but not emergency and medium effort, there is less mush. The bite is more instantaneous, but there is still mush. With this amount of effort, it does get through the mush spot quicker.

 

My own WRX has Autozone OEM replacement rotors, OEM pads, rear H6 rotor upgrade, and Goodridge SS lines. There is no initial mush and they are much more sensitive to tapping. But when I stand on them in greater than medium effort, it doesn't have that friction-kinda feeling. I suspect that is due to the pads since I recently went from Axxis Ultimate to OEM and didn't experience this before. I'm hoping the STI MC/BB gets the OBXT closer to this WRX-like feeling.

 

So how does it feel now?

 

There is what feels like .5" pedal travel. There is no more mush, none at all. At the bottom of pedal depression, it feels like the brakes do not clamp. Stomp it harder and nothing noticeable happens except that it feels like the wheels continue to move and the pads aren't clamping. This could be the tires, the pads, a number of different things. But it isn't better than before.

the point of this swap was to firm up the feel, not improve actual braking.

i believe it works as intended.

 

maybe you need better rotors and pads

Fenominal

I will say if you have aftermarket calipers like brembos, wilwoods, stoptech etc etc

 

you will feel even less travel than the LGT calipers.

 

The difference in the two is the stock calipers are slide style calipers meaning the caliper actually moves to grip the rotor.

 

The HP aftermarkets are fixed and pistons on either side pinch the caliper.

 

The braking with the aftermarkets is quicker and as I remember a bit more firm yet.

 

Here is my review when I put the wilwoods on from Eric at brakeswap

 

http://legacygt.com/forums/showthread.php/brakeswap-com-performance-brake-kit-lgt-installed-outback-xt-102549.html?t=102549&highlight=wilwood+install

 

Ill let you know how mine turns out as soon as I get around to doing it.

I'm sorry, I mistook the purpose of the swap to mean functional, as in it provides an actual benefit to the performance of the brake system. In that case, yes, the swap absolutely firms the pedal and reduces the length of pedal travel. But it also completely negates all "feel," and I'm wondering if it's actually worse because of it.

 

I have brand new rotors and pads, both of which are better than stock. They meet the function of my budget and intended use. My point in commenting is to spread the word that this swap is not really an upgrade, that it isn't functional or superior in providing better stopping power, and that it is essentially just costly swag (though some of that cost is saved if you do the labor yourself; I don't have the space or the tools).

 

My comment serves to inform those, like me, who expected otherwise.

 

In the future, I'll upgrade to a racier pad to provide what I had originally intended to achieve.

 

the point of this swap was to firm up the feel, not improve actual braking.

i believe it works as intended.

 

maybe you need better rotors and pads

Fen i directly disagree with you on the opinion that this is swag.

 

Of course changing the master and booster isnt going to provide a stronger brakeing system, this is a very basic concept and the fact that you didnt understand the first go around makes me second guess your general car knowledge.

 

The purpose for me doing this, and many others, was to remove pedal take up, mush at the top of the pedal travel, AND the sudden ballooning in the braking force that you subsequently have once your pads finally engage. Why? Because there is an ungodly amount of this on most OEM and/or modified OEM LGT braking systems.

 

Negates all feel? Please go into this further. There are three components of feel; pressure, a corresponding increase in brakeing force with the addition of more pressure, and the ability to modulate the brakes at lockup. ALL of these functions, in my experience, were improved apon, ESPECIALLY compared to the severely lack luster OEM booster and master.

 

It may not be perfect, if thats what you were shooting for, but it is sure as hell alot better then the OEM.

I'm sorry, I mistook the purpose of the swap to mean functional, as in it provides an actual benefit to the performance of the brake system. In that case, yes, the swap absolutely firms the pedal and reduces the length of pedal travel. But it also completely negates all "feel," and I'm wondering if it's actually worse because of it.

 

I have brand new rotors and pads, both of which are better than stock. They meet the function of my budget and intended use. My point in commenting is to spread the word that this swap is not really an upgrade, that it isn't functional or superior in providing better stopping power, and that it is essentially just costly swag (though some of that cost is saved if you do the labor yourself; I don't have the space or the tools).

 

My comment serves to inform those, like me, who expected otherwise.

 

In the future, I'll upgrade to a racier pad to provide what I had originally intended to achieve.

 

maybe you could take the scientific approach and do a before and after test case between the stock booster+mc and the sti swap to confirm if your beliefs/expectations are true.

what you feel/think may contradict the hard tested data.

 

use same braking force (as best as you can gauge), and measure distance from same speeds to full stop.

something like that.

 

as for me, im pleased w/ the results.

i also have a 'racier' brake setup, so the difference was staggering.

I just installed mine today. It was kind of a pain to get the booster in and out,but I took out the intercooler and was able to squeeze it out. At the same time i flushed everything with ate super blue. I drove it home from work and the brakes we dragging hard so I unbolted the master and adjusted it and it feels fantastic. I feel like there's a lot of things you could do that cost ~80-100 bucks that don't make any noticeable difference and since this mod is all about feel it does what is expected. I really hated the way my pedal felt prior to doing this and I recommend anyone who has the time,money and the means to do it,to do it.

unbolted the rod and adjusted? Not the master correct?

 

Good to hear, be doing this soon.....

Fen i directly disagree with you on the opinion that this is swag.

 

Of course changing the master and booster isnt going to provide a stronger brakeing system, this is a very basic concept and the fact that you didnt understand the first go around makes me second guess your general car knowledge.

 

The purpose for me doing this, and many others, was to remove pedal take up, mush at the top of the pedal travel, AND the sudden ballooning in the braking force that you subsequently have once your pads finally engage. Why? Because there is an ungodly amount of this on most OEM and/or modified OEM LGT braking systems.

 

Negates all feel? Please go into this further. There are three components of feel; pressure, a corresponding increase in brakeing force with the addition of more pressure, and the ability to modulate the brakes at lockup. ALL of these functions, in my experience, were improved apon, ESPECIALLY compared to the severely lack luster OEM booster and master.

 

It may not be perfect, if thats what you were shooting for, but it is sure as hell alot better then the OEM.

 

Swine,

 

I'm not intending to create a thing. I'm only trying to set the record straight for others such as myself, who maybe don't know as much and who just see "OMG TEH BRAKE MOD IS TEH AWESOMEZ! (I'm NOT a brake expert, but I am a writer, and my intent here is to describe clearly what this mod DOES and does NOT do.)

 

We could both have the exact same mods, and if installed by two different sources, could have completely different feeling cars. The constant is reduced pedal travel. If that was your goal, then the object is achieved. This mod significantly reduces pedal travel and mush.

 

I am simply arguing that this may not be a good thing. Obviously, I can't perform a scientific study to actually verify whether one performs better than the other.

 

In my case, which may not be what others experience (due to variance), I believe that the "feel" in the mush may be better than the no feel in the non mush. If that sounds weird, allow me to explain: mush is a feel. With mine, I could feel the engagement, but it happened low in the pedal travel, closer to the floor. Now, with no mush, there is no feel, no engagement. The pedal simply moves what feels like a half inch, then it doesn't move at all any further. Stomp on it and that pedal isn't moving more than half an inch, and once it reaches that point, it doesn't actually clamp up any better than before. It actually FEELS like it doesn't clamp as well.

 

As for your three points, it would be nice if we could measure it. But, it is my opinion that this mod a) does increase pressure, but not beneficially b) does NOT increase braking force, c) does NOT increase the ability to modulate.

 

It simply reduces pedal travel and lessens mush, which comes, in my case, at least, with decreased feel and confidence.

^

 

which basically means, "to each his own." I would rather have some mush and some feel than no mush and no feel.

^

 

which basically means, "to each his own." I would rather have some mush and some feel than no mush and no feel.

 

Agreed, my only agruement against that is that i felt specifically that braking feel greatly improved(imo).

 

If you prefered the feel of the OEM brakes, then so be it, there is nothing else to discuss here.

 

I particularly found the brakes to feel more like a BBK/other sports cars brakes ive had the opportunity to get track time in, and greatly prefered that feeling and how it translated into my braking action while driving athletically/on the track.

Agreed, my only agruement against that is that i felt specifically that braking feel greatly improved(imo).

 

If you prefered the feel of the OEM brakes, then so be it, there is nothing else to discuss here.

 

I particularly found the brakes to feel more like a BBK/other sports cars brakes ive had the opportunity to get track time in, and greatly prefered that feeling and how it translated into my braking action while driving athletically/on the track.

 

Nooo, I HATED the stock brakes, which is why I looked into this. I was confident that LGT calipers, stoptech rotors and pads, SS lines, and the GS MC brace would significantly better both the feel and performance of the brake system. There was a minimal benefit. I again expected a significant benefit to the STI MC/BB mod. The change was significant, but I don't believe beneficial.

 

Now? I want to drive your car.

So does this mod reduce feedback from the brakes? Or is that just Fenominal's impression?

ok i did the brake swap for my 2.5i legacy. (STI MC and BB). i have a situation that i hope someone could help clear up for me. my brake pedal feels very soft hardly any resistance. when i press down on the pedal its very soft and then about 2-3 inches down my brake pedal stops almost like something isnt letting it compress. My car brakes when i press down on the brakes slightly but like i said it feels like theres no resistance at all in the pedal travel. does that make sense to you guys? i bench bleed the MC and bleed the brakes twice but for some reason i feel it has something to do with the brake booster rod length. When i uninstalled my stock brake booster i measured the rod length and then adjusted the STI booster to the same length. When i installed the STI BB rod to the back of the brake pedal the brake pedal didnt push out far enough to hit the brake light switch that turns the brake lights off. I didnt realize the brake pedal wasnt touching that switch and my battery died. Anyway i had to re adjust the rod and make it longer, but i think thats the reason why i have this really soft pedal with hardly no resistance for about 2-3 inches and then the pedal stops and doesnt compress. Sorry for the long explanation but im not to sure whats going on with my car.

ok i did the brake swap for my 2.5i legacy. (STI MC and BB). i have a situation that i hope someone could help clear up for me. my brake pedal feels very soft hardly any resistance. when i press down on the pedal its very soft and then about 2-3 inches down my brake pedal stops almost like something isnt letting it compress. My car brakes when i press down on the brakes slightly but like i said it feels like theres no resistance at all in the pedal travel. does that make sense to you guys? i bench bleed the MC and bleed the brakes twice but for some reason i feel it has something to do with the brake booster rod length. When i uninstalled my stock brake booster i measured the rod length and then adjusted the STI booster to the same length. When i installed the STI BB rod to the back of the brake pedal the brake pedal didnt push out far enough to hit the brake light switch that turns the brake lights off. I didnt realize the brake pedal wasnt touching that switch and my battery died. Anyway i had to re adjust the rod and make it longer, but i think thats the reason why i have this really soft pedal with hardly no resistance for about 2-3 inches and then the pedal stops and doesnt compress. Sorry for the long explanation but im not to sure whats going on with my car.

 

I can't comment on the installation procedure since I'm a tool dummy (I don't have space or tools), but the pedal feel that you describe is somewhat consistent with what I described. The biggest difference is your estimation of the pedal travel (2-3 inches) versus my estimation of pedal travel (.5 inch). But yes, mine feels the same, in what you described, as "no resistance."

 

It just stops, right?

FYI - per subarupartsforyou.com all of these share the same master cylinder, part# 26401AC191 which should be the 17/16" version:

• 04-07 STi
  
• 03-05 Impreza ALL exc WRX AT
  
• 06-07 Impreza non-turbo
  
• 02 Impreza w/ ABS
  

Just some more options to search. On eBay Impreza parts generally seem cheaper than STi (surprise!). I've not been able to find the same cross-reference info for brake boosters (04-07 STi = F01G061023?). I just ordered my parts and the MC brace so I'll get to see the relative merits of each on an already-Brembo'ed LGT wagon.

Edited November 5, 2012 by BlackHole

Still havent gotten around to do mine yet but I found a write up on the forester forum. I'd imagine it's somewhat similar to our setup

 

http://www.subaruforester.org/vbulletin/1315326-post84.html

 

and one for bench bleeding the MC

http://www.subaruforester.org/vbulletin/f68/bench-bleeding-master-cylinder-118834/

By chance could someone measure the diameter and depth of the STi brake booster? I'm swapping a EJ208 into my Outback (I know, it's not a GT, but the Outback guys seem to be useless for performance mods!). Anyway, the stock brake booster won't clear the turbo on the LH side, but it looks like the STi booster is actually smaller.

10" diameter. 4.25" from firewall mounting surface to base of master cylinder. All measurements are approximate since I didn't have a caliper but only a tape measure and eyeballs. Edited November 15, 2012 by BlackHole

ok i did the brake swap for my 2.5i legacy. (STI MC and BB). i have a situation that i hope someone could help clear up for me. my brake pedal feels very soft hardly any resistance. when i press down on the pedal its very soft and then about 2-3 inches down my brake pedal stops almost like something isnt letting it compress. My car brakes when i press down on the brakes slightly but like i said it feels like theres no resistance at all in the pedal travel. does that make sense to you guys? i bench bleed the MC and bleed the brakes twice but for some reason i feel it has something to do with the brake booster rod length. When i uninstalled my stock brake booster i measured the rod length and then adjusted the STI booster to the same length. When i installed the STI BB rod to the back of the brake pedal the brake pedal didnt push out far enough to hit the brake light switch that turns the brake lights off. I didnt realize the brake pedal wasnt touching that switch and my battery died. Anyway i had to re adjust the rod and make it longer, but i think thats the reason why i have this really soft pedal with hardly no resistance for about 2-3 inches and then the pedal stops and doesnt compress. Sorry for the long explanation but im not to sure whats going on with my car.

 

there are 3 methods for bleeding the system. 1 for the BB bench bleed (which i dont like, its just as easy to bleed it on the car). this is because some dont get the knack of the install and flipping the MC around, up, over in and and out a dozen times may get air in it. so just bleed in the car.

methods 2 and 3 are for bleeding the brake lines. one is for a fresh start, new fluid throughout empty brake lines (or with massive air). two is if you are just bleeding to push fluid near the caliper out from pure stock in the reservoir . look in the service manual for your car. read the whole section on brakes and MC BB install. it will list both.

if done incorrectly (in order or process) you will have air and have a mushy pedal or late engagment.

 

as for ajdusting the push rod; dont use the measure your stock one and match method. this can be missleading as i think different versions rods are different lengths. this was the case in mine. just adjust the new rod to meet the pedal and light kill switch. see how i did it on page 2 or 3.

good luck

Edited November 17, 2012 by triple_B

Originally Posted by Swine

Fen i directly disagree with you on the opinion that this is swag.

 

Of course changing the master and booster isnt going to provide a stronger brakeing system, this is a very basic concept and the fact that you didnt understand the first go around makes me second guess your general car knowledge.

 

The purpose for me doing this, and many others, was to remove pedal take up, mush at the top of the pedal travel, AND the sudden ballooning in the braking force that you subsequently have once your pads finally engage. Why? Because there is an ungodly amount of this on most OEM and/or modified OEM LGT braking systems.

 

Negates all feel? Please go into this further. There are three components of feel; pressure, a corresponding increase in brakeing force with the addition of more pressure, and the ability to modulate the brakes at lockup. ALL of these functions, in my experience, were improved apon, ESPECIALLY compared to the severely lack luster OEM booster and master.

 

It may not be perfect, if thats what you were shooting for, but it is sure as hell alot better then the OEM.

Swine,

I'm not intending to create a thing. I'm only trying to set the record straight for others such as myself, who maybe don't know as much and who just see "OMG TEH BRAKE MOD IS TEH AWESOMEZ! (I'm NOT a brake expert, but I am a writer, and my intent here is to describe clearly what this mod DOES and does NOT do.)

We could both have the exact same mods, and if installed by two different sources, could have completely different feeling cars. The constant is reduced pedal travel. If that was your goal, then the object is achieved. This mod significantly reduces pedal travel and mush.

I am simply arguing that this may not be a good thing. Obviously, I can't perform a scientific study to actually verify whether one performs better than the other.

In my case, which may not be what others experience (due to variance), I believe that the "feel" in the mush may be better than the no feel in the non mush. If that sounds weird, allow me to explain: mush is a feel. With mine, I could feel the engagement, but it happened low in the pedal travel, closer to the floor. Now, with no mush, there is no feel, no engagement. The pedal simply moves what feels like a half inch, then it doesn't move at all any further. Stomp on it and that pedal isn't moving more than half an inch, and once it reaches that point, it doesn't actually clamp up any better than before. It actually FEELS like it doesn't clamp as well.

As for your three points, it would be nice if we could measure it. But, it is my opinion that this mod a) does increase pressure, but not beneficially b) does NOT increase braking force, c) does NOT increase the ability to modulate.

It simply reduces pedal travel and lessens mush, which comes, in my case, at least, with decreased feel and confidence.

Fen,

i fear you are making things a bit worse. you mentioned yourself that you dont know much and dont have the time and you just write. your deduction in describing "feel" is flawed by personal bias. it has no empirical data just your own "i think" and "i feel".

i track my car a lot in Washington. contrary to popular myth we have nice hot weather here and it does rain a lot. often in the same day. track conditions are fun and you get them all. prior to this mod my pedal often went to the floor and in dire straights in hot times i would run out of pedal stroke and loose braking ability. as a side not i do not ride my brakes and i am a very late braker so i dont over heat and toast pads rotors or fluid.

the "mushy" pedal you like or would like is odd in my approach and practice. if i need to modulate my brake pressure i dont want to pump my entire leg up and down 2 inches in a mushy stroke to find the g-spot. i LOVE my slight toe pressing to modulate. even with the ABS i love what this mod has done. i put my foot down late and hard and if a tire doesnt like it all i do is curl a toe for the correct pressure and all is perfect. this occurs at the top of the pedal.

for giggles i buried (or tried to bury due to pressure and instant contact) the pedal and it will overwhelm the ABS and its a slick 4 wheel squeal. so its got bight! and thats with at temp Star Specs.

as for measuring clamping pressure (and/or line pressure) there is a tool for that. ive read about it but dont have one. could be an easy thing to come across.

as for thinking this mod does NOT change pressure you are wrong. changing bore piston and stroke in the MC all affect pressure. also, by not bottoming out stock setup i also dont loose braking ability.

i cant recall now if the STI/WRX MC piston/bore is smaller or larger than stock LGT or if its stroke (length) is different (if someone wants to cut one open or find the spec it would be great). as math would have it a larger bore is less pressure via equal work but if the stroke changes so does the amount of fluid moved by the piston in the bore before moving into the brake lines (again, if stroke changes so does pressure). assuming the mod is a larger bore i might have to push harder now to get increase in pressure but by no longer bottoming out with "mushy" pedal i get engagement 'instantly' and can continue applying more force (aka pushing harder with foot) to increase pressure and push pads harder. this increase in pressure on track pads and wider sticker tires allows greater braking force to be applied before loss of traction. ie i stop faster.

line pressure could also be affected if the brake lines in the LGT are a different i.d. size than the STI/WRX. if they are this would again be an area for math with volume and pressure change that would affect brake torque.

happy braking and here are some fun reads.

http://www.automedia.com/Better_Brake_Performance/pht20080501gh/1

http://www.popularhotrodding.com/tech/0601phr_braking_systems/viewall.html

http://stoptech.com/technical-support/technical-white-papers/brake-system-and-upgrade-selection

Edited November 17, 2012 by triple_B

Originally Posted by Swine

Fen i directly disagree with you on the opinion that this is swag.

 

Of course changing the master and booster isnt going to provide a stronger brakeing system, this is a very basic concept and the fact that you didnt understand the first go around makes me second guess your general car knowledge.

 

The purpose for me doing this, and many others, was to remove pedal take up, mush at the top of the pedal travel, AND the sudden ballooning in the braking force that you subsequently have once your pads finally engage. Why? Because there is an ungodly amount of this on most OEM and/or modified OEM LGT braking systems.

 

Negates all feel? Please go into this further. There are three components of feel; pressure, a corresponding increase in brakeing force with the addition of more pressure, and the ability to modulate the brakes at lockup. ALL of these functions, in my experience, were improved apon, ESPECIALLY compared to the severely lack luster OEM booster and master.

 

It may not be perfect, if thats what you were shooting for, but it is sure as hell alot better then the OEM.

Fen,

i fear you are making things a bit worse. you mentioned yourself that you dont know much and dont have the time and you just write. your deduction in describing "feel" is flawed by personal bias. it has no empirical data just your own "i think" and "i feel".

i track my car a lot in Washington. contrary to popular myth we have nice hot weather here and it does rain a lot. often in the same day. track conditions are fun and you get them all. prior to this mod my pedal often went to the floor and in dire straights in hot times i would run out of pedal stroke and loose braking ability. as a side not i do not ride my brakes and i am a very late braker so i dont over heat and toast pads rotors or fluid.

the "mushy" pedal you like or would like is odd in my approach and practice. if i need to modulate my brake pressure i dont want to pump my entire leg up and down 2 inches in a mushy stroke to find the g-spot. i LOVE my slight toe pressing to modulate. even with the ABS i love what this mod has done. i put my foot down late and hard and if a tire doesnt like it all i do is curl a toe for the correct pressure and all is perfect. this occurs at the top of the pedal.

for giggles i buried (or tried to bury due to pressure and instant contact) the pedal and it will overwhelm the ABS and its a slick 4 wheel squeal. so its got bight! and thats with at temp Star Specs.

as for measuring clamping pressure (and/or line pressure) there is a tool for that. ive read about it but dont have one. could be an easy thing to come across.

as for thinking this mod does NOT change pressure you are wrong. changing bore piston and stroke in the MC all affect pressure. also, by not bottoming out stock setup i also dont loose braking ability.

i cant recall now if the STI/WRX MC piston/bore is smaller or larger than stock LGT or if its stroke (length) is different (if someone wants to cut one open or find the spec it would be great). as math would have it a larger bore is less pressure via equal work but if the stroke changes so does the amount of fluid moved by the piston in the bore before moving into the brake lines (again, if stroke changes so does pressure). assuming the mod is a larger bore i might have to push harder now to get increase in pressure but by no longer bottoming out with "mushy" pedal i get engagement 'instantly' and can continue applying more force (aka pushing harder with foot) to increase pressure and push pads harder. this increase in pressure on track pads and wider sticker tires allows greater braking force to be applied before loss of traction. ie i stop faster.

line pressure could also be affected if the brake lines in the LGT are a different i.d. size than the STI/WRX. if they are this would again be an area for math with volume and pressure change that would affect brake torque.

happy braking and here are some fun reads.

http://www.automedia.com/Better_Brake_Performance/pht20080501gh/1

http://www.popularhotrodding.com/tech/0601phr_braking_systems/viewall.html

http://stoptech.com/technical-support/technical-white-papers/brake-system-and-upgrade-selection

 

 

triple_B,

 

Let me elaborate again.

 

I don't have tools. I don't have knowledge of tools. Until recently, I didn't even have space for tools. I certainly don't have money for tools. I am that guy that has to pay for everything. It's not economical, but that's the way it is.

 

When I say I don't have experience, or that I lack brake knowledge, what I mean is that I don't know the brake lingo to describe what I feel. I'm certainly no expert on the matter, but from experience, I know when something is good, or not good. But my knowledge is limited to stock function. I can't tell you how long a pad will last on a track, or how long on a track until the brakes get too hot and don't work.

 

I've driven more than 80 2012-2013 new cars this year (and more than 40 2011's last year). All of them stock, and from the manufacturer. Yes, our '05-06 LGT/OBXT's are now a few years old, and there should be some expectation for regression due to wear and age, etc. But I can say that my stock OBXT was the worst feeling and performing braker among all those cars that I drove. Ordinarily, this could be an isolated incident. My car may have a problem that others do not. But, I found on this forum and on Outback.org, that my brake disappointment is not an isolated matter.

 

This modification, as I understood it, would better brake performance. I do not believe that it does this. You are correct, however, that empirical data would tell. I don't have or know of a way to do this. After all, even tires will make a noticeable difference. You would need to have an identical setup, before and after, to accurately conclude a realistic sample.

 

When I describe mush, I don't mean that I like mush. I mean that mush is an actual feeling. There's something there, something happening. Yes, it's not a great thing, but it's a reliable thing in that it's there and you know what's happening. You can count on it and you can adapt to it. With my setup now, there's no indication of any level of brake pressure, meaning, the travel is so waaaaaay short and that there's no feeling from initial clamp to lockup, you have to slam on the pedal to stop at a stop sign, and you have to slam on the pedal with equal force to get it to stop emergency like. See what I mean? With the stock MC/BB, one can casually stick the foot through the jello with just a little pressure to stop at a stop sign, and one can distinguish that, in an emergency, one can stomp on it, to the bottom of its travel, to stop for an emergency. My setup now requires the same hard effort everytime, in every situation.

 

I drove a 2013 Nissan Altima yesterday for a 5-car midsize sedan comparison that I'm writing. Of the five cars, it had the most sensitive brakes, meaning that it was easy to lock them up, that it only needed a little bit of pressure to stop quickly. If my OBXT with STI MC/BB had the same short pedal throw as it does now, but acted like the Altima, then I wouldn't be complaining. My discontent stems from the fact that performance is not improved, and that brake feel has disappeared. The only "advantage" I see is that brake pedal travel has ben reduced.

 

The ace up my sleeve (an appeal to professional authority) is that underground racing legend, John Mueller, who last week built me a custom-fabricated coilover to fix my wretched suspension, commented that the current setup and its travel is dangerously bad. As in, something is very wrong. I didn't tell him about this swap, but I did tell him about the new calipers, rotors, pads, SS lines, and MC brace. All have about 4-5k and were installed at the same time.

 

With that novel said, I believe these are the most plausible conclusions:

 

1. I have a bad installation

2. I have bad/wrong parts

3. This swap is a bad idea

4. I'm a know-nothing idiot

 

I would strike out number 4 based on the professional opinion of John Mueller (and his staff, who drove the car separately), who, without my prompting, and without knowledge of the swap, told me that something there is very wrong. When I get the time, I'm planning on semi-interviewing him about the coilover he designed for me. I'll get him to geek-talk comment on my brakes, too.

 

I hope this clarifies my thoughts, at least until I can get the professional opinion and his professional words.

 

- Jason

After about a year, I finally put my STI MC/BB back on my Legacy GT. I had initial problems a year ago with all four brakes locking up before we all knew that this was an issue of pushrod length. I'm glad to be back w/ the STI setup for pedal feel. It markedly firms the pedal and increases pedal sensitivity. I don't note any improvement in actual braking distance though.

 

A few summary points with my re-install:

 

The Grimmspeed MC brace fits with the STI MC but its close. In addition, I had to redrill a new hole for the piece of the brace that has the threaded rod pushing against the MC. I had to drill the hole about 1/4" below the existing hole to contact the MC near the center of its diameter.

 

To adjust the pushrod, I would start with approximately 6 threads showing distal to the lock nut. Stock Legacy GT MC had 5 threads showing but this locks up my brakes if I leave it the same. If you want the pedal firmer, then turn the pushrod so that less threads are showing (longer pushrod length). If the pedal is too firm and the brakes lock up, turn the push rod so more threads are showing, ie 7-8 (shorter rod). The brakes locking up sucks and it can take a few hours to depressurize. Unhooking the brake booster vacuum line though may relieve enough pressure to get it unlocked though. Err on the side of a looser pedal to begin with (ie maybe 7-8 threads showing).

 

Make sure that the brake light sensor activates with the slightest tap of the brake pedal. If it doesn't, this sensor can be adjusted quite easily with the two lock nuts.