STI Master Cyl. and Brake Booster SWAP SUMMARY for LGT

I wanted to thank everyone who pioneered this mod, and took the time to post their experiences, problems and solutions. Most appreciated!!! I undertook this myself and I thought I would write a review (if TL, then DR, but will attempt to make this helpful - apologies for duplication) covering the concerns and tricky bits encountered in return.

The part set I used came complete from an 06 STI (booster - "SJ", reservoir, 1 1/16 MBC, vacuum line + check valve).

 

I have had the car for near 2 years now, and have done everything less drastic to cure the legitimately awful brake feel with little avail (caliper work, sliders, sanding/rebedding, fluid (like 10 bleeds -_-), HPS pads, rotors, Grimspeed MBC brace). Clearly the 15/16th bore cylinder is the problem in this car. The difference in FEEL is like night and paper, not to mention heel toe capability . As noted by previous posts, and common sense, this will increase pedal effort significantly, but also induce that "wooden" element. If anyone has any ideas on where to go from here regarding that then woo hoo. I won't rest until these brakes rock.

 

General procedure taken in order:

1) PB Blast hard lines

2) Disconnect brake clevis pin, unbolt booster from firewall (cabin side)

3) Remove TMIC, bracket. Moved other lines in the way (A/C, harness down the driver strut tower, heater core hoses...etc)

4) Un-tensioned my MBC brace (not a stock piece). If you have one (and questions were posed on this in this thread), you do not need to remove it from car to do this mod, simply un-tension it and remove the preload bolt

5) 10mm flare nut wrenched the hard lines (highly recommend to use a flare nut...), pulled the vacuum line and check valve

6) Wiggled out the assembly

7) Inserted check valve from STI vacuum line into stock LGT line. Used generous amounts of lube, and the back end of a 3/8ths ratchet to force it in. BULLET SIDE points to intake manifold

8) Adjusted booster push rod to the recommended 6 threads (note: this utterly failed for me - see below section for more on this)

9) Inserted STI assembly. Don't be a fool like me and bolt up the booster, then try to assemble the pedal pin.

10) Leave the bolts undone on the booster so it can be maneuvered longitudinally as required to allow the pedal to meet the rod at the right distance. Pop in the brake clevis + cotter pin.

11) Now bolt up the booster snug

12) Once proper rod length is dialed in, make sure your brake lights activate at the correct pedal distance

13) Reassemble/undo anything in the way in the engine bay

14) Go heel toe some corners

 

Concerns encountered from inception to completion:

1) I live in Canada, and was having significant trouble finding the correct parts around here/ebay even. Tons of JDM stuff exists on the market, however those are less than ideal (basically it is not worth the trouble). I eventually found the full USDM LHD part system needed (new ebay post ftw!)

a) Getting a JDM MBC means the second hard line bolts up on the opposite (RHD) side - So you would be into extending existing brake hard lines...

b) The booster line input is also on the opposite side - So you would be into extending the stock hose over or around the system to fit it up. Less of an issue than the hard lines but still a PIA

2) Check valve and hose are available with same P/Ns here in Canada from the dealer with no sweat, so acquiring that incredibly small but useful part is no issue

3) Was worried about introducing air into the system, and therefore into the ABS actuator. Sent about 300ml of fluid through each rear line, and 150-200 through each front on the final bleed. Have not seen any problems yet.

4) Bleed order is contradictory, even within Subaru documentation. I used RR, RL, FR, FL in accordance with past experience.

5) Bench bleeding was accomplished with the purchase of one brake hard line with "standard fitting" ends, and a roll of washer fluid hosing. Hard line was cut in two with a pipe cutter to reduce the chance of creating metal shards, then threaded into the MBC. Rubber lines were attached at opposing ends and routed to the reservoir. A 1/4 socket extension was used to pump the cylinder ~50 times (Until I saw crap stop pouring out of it - fluid changed 3 times). Used line pinchers to clamp each end to make it from bench to firewall without introducing air.

6) As mentioned, I used 6 threads on the rod. This did not even meet up with the pin, so I backed it off to probably 8 while on car. Even this locked the crap out of my brakes as others have experienced (you will notice it within 3-5 min of driving and it becomes undrivable). I will post an edit if I remember as to the exact number I use when I actually nail it correctly (hopefully tonight). If you feel the pedal activate the brakes within 1/2-1cm of travel, she ain't gonna work!

7) TO FIX BRAKE LOCK UP WHILE OUT DRIVING: Don't listen to girlfriend and brother about calling CAA... Pop the hood, remove vacuum line from booster (under a lot of suction). Brakes will unlock instantly. Limp home on alternate forms of braking + whatever possible on the pedal. Readjust accordingly.

8) Clearance issue on the new booster. It does hit the hard lines on the firewall as mentioned by previous posters. I felt a pain go through my heart every time I hammered the rim to adjust its shape, ergo I just got some rubber padding and protected the affected lines instead.

 

That should do. Hope it was helpful. I am sure happy with this mod!

Cheers

Edited June 4, 2014 by taka
Dope hit reply before finishing

So can a 07-14 model STI brake booster and MC be used for this mod or does it need to be an 04-05?

edit I am stupid^^ Edited October 9, 2014 by RallyMachine

Nope, that model year range won't do.

I have an extra STI MBC if needed.

If anyone is interested. I still have my Sti booster and MC with the required booster brake line. Sitting in Storage.

 

First $95 gets it. That's shipped and tracked.

Sub'd.

 

Bought an 05 mc/bb from eBay this past week, will be installing sometime in the near future-

 

Will likely be installed with new pads and ss lines, so won't be able to comment on - from stock performance, but will offer feedback nonetheless.

Are you going to be installing a new shortblock along with that?

 

I am curious how much of an increase over stock that combined upgrade will be. Let us know when you finish the install.

Hey guys, I want to perform this swap in LGT 05 with AUTO trans. I see there are 2 different STI 04-05 MCs and Boosters; 1 for manual and 1 for auto.

 

Sounds like a dumb question, but do I need to put the AUTO version only? Looks like it's pretty hard to find them on eBay and brand new, there are pretty expensive...

 

thanks!

I don't see why they would be different... unless it has something to do with one of Subaru's hill holder features. But, the STI never came in an auto, at least not in that generation

Hey guys, I want to perform this swap in LGT 05 with AUTO trans. I see there are 2 different STI 04-05 MCs and Boosters; 1 for manual and 1 for auto.

 

Sounds like a dumb question, but do I need to put the AUTO version only? Looks like it's pretty hard to find them on eBay and brand new, there are pretty expensive...

 

thanks!

 

Yeah, I bought like, the last one, apparently. Went looking for them shortly after mine arrived, to send a link to a friend and there were none to be found.

 

Check valve shouldn't make a difference, AT/MT.

Thanks Taka and MrTris, I just bought this one: http://www.ebay.com/itm/130950504539

[important] tip so you don't have to guesstimate the correct number of turns on the clevis:

 

 

 

After removing your stock brake booster,

 

 

1) Grab some calipers and measure the distance from the clevis hole to the mounting surface of the stock brake booster.

 

2) Adjust the clevis on the STI brake booster so the distance from the mounting surface to the clevis hole matches the stock distance.

 

 

Continue installation.

 

 

 

Doing this will ensure the correct clevis distance is hit the first time. No further adjustment is required to reduce play or scary/dangerous overheating situations on the highway. As always, drive carefully after the mod is performed and check for leaks or signs of strange performance before driving hard. Don't forget to install the check valve in the brake booster vacuum line.

 

Hoon responsibly.

 

 

 

 

 

 

*Photo taken and edited from another post in this thread (posted by sjwelna). Stock MC/BB on right, STI unit on left.

Edited January 26, 2015 by legacybt
Photo Credit

Good stuff. I should have done that ^

 

For the record, I decided to try the 1 inch MBC out of an 06 WRX recently, and like the performance better.

When initially deciding between the WRX and STI units, I attempted some shoddy math, and that told me the STI part should end up being closer to a stock set up on a WRX.

In short I compared master cylinder bore sizing in relation to the calipers - noting that the fronts are 2 pot, and the whole system uses sliding (so x2 on travel for that). Like I said, the STI numbers came out better, but there are other factors such as the pedal geometry...etc.

 

TDLR: I recommend sourcing a WRX 1 inch MBC over the 1 1/16th STI part, unless your pants get all hot knowing you have some diseased parts in your car...

Subscribed for later mod!

 

Taka - got a PN for that WRX MBC?

 

Anyone else follow Taka's lead and do the WRX MBC? More data is always good...

This is from my notes at the time.

 

Required Parts:

Master Brake Cyl - 04-07 STi (1,1/16") OR 06-07 WRX (1")

Booster - shared between STi and WRX in generation

Vac hose - with check valve

 

Local Dealer Quoted Part Numbers (Subaru of Mississauga - near Toronto ON):

STi Hose P/N: 26140FE131

STi 02-07 MBC: 26401AC191

Booster: 26402FE400

 

Looks like I didn't record the WRX MBC part number because it was an after thought mod. I am sure with a quick call or some trolling you could find it. It is pretty simple, you just need the part from an 06/07 car. Make sure that is the case, and it is stamped "Nabco Japan 1""

 

The stock brake feel on this car was about the worst thing I have ever felt, including neglected sunfires. Absolutely essential IMO to do something about this. It will never be amazing on the stock calipers (the large 2 pot sliding units seem to just always give a pudding like feel), but doing this mod can make the brakes acceptable. It has been my biggest issue with these cars.

 

Since doing this myself, I have switched from Hawk HPS to Stoptech streets on all 4 corners. So far that has been an excellent choice - god I hated the Hawks on this set up. With the Stoptechs, feel is up, initial bite is up, and hot performance seems better if anything (no track time, just auto x and hard street driving). If I had more money to throw at testing, I would want to try something more OEM like and see what that does for initial bite. If anyone has done that, I would be curious to chat about your experiences.

 

PM me if inclined. Happy to help with this if able.

 

PS: I have an STi master cylinder if anyone wants to give that a try to see which set up you like better. Ship it out for cheap I don't care lol.

Edited June 25, 2015 by taka
Added

Ok, I've been thinking of doing this. Forgive my lack of knowledge but I've heard the 2008 Spec B has a VDC, what does that entail?

So, has anyone tried just swapping the master cylinder but not the brake booster? Is there a significant difference between our brake booster and the STi one?

Just a note on pads. I have an STI MC/booster in my basement I haven't gotten around to installing. Stock rotors and calipers, SS lines. Street driven car, my wife's DD. I also tried the Hawk HPS (hated them, soft), then Stoptech Street Performance (massive issues with pad deposits, shuddering brakes). Now I have the new Hawk HPS 5.0. Very nice, rock solid pedal, excellent bite, no deposits. I like these a lot. I don't feel the need to try the STI MC setup with these pads.

 

 

Since doing this myself, I have switched from Hawk HPS to Stoptech streets on all 4 corners. So far that has been an excellent choice - god I hated the Hawks on this set up. With the Stoptechs, feel is up, initial bite is up, and hot performance seems better if anything (no track time, just auto x and hard street driving). If I had more money to throw at testing, I would want to try something more OEM like and see what that does for initial bite. If anyone has done that, I would be curious to chat about your experiences.

 

PM me if inclined. Happy to help with this if able.

 

PS: I have an STi master cylinder if anyone wants to give that a try to see which set up you like better. Ship it out for cheap I don't care lol.

So, has anyone tried just swapping the master cylinder but not the brake booster? Is there a significant difference between our brake booster and the STi one?

 

The bolt holes won't line up. With the LGT they are at like 10 and 4 o'clock. WRX parts are 9 and 3. Gotta go with a booster from the rex or sti (same part as far as I know)

 

emosound, interesting experiences.

For me I found the HPS pads were utter crap as well, but more significantly the deposits and spalling were HORRIBLE!!!! Never ever again on this car.

You didn't like the Stoptechs eh? I have not tried any other pads except the HPS, Stoptechs and mystery stockers. The Stoptechs imo with this set up are far superior. They actually feel fairly good (provided you beat on them once a week or so, else they loose bite) and I found no depositing issues with these on stock rotors. Maybe the difference between the HPS and these has clouded my judgement and not allowing me to see beyond, but I am in love with them haha. What are the HPS 5.0s all about? I can definitely go for more bite if these provide

 

Did you find the SS lines helped alot? Curious as to your full review on that before and after.

 

Cheers,

Edited October 19, 2015 by taka

This car is weird. I had awful problems with deposits with the stock rotors and pads from new. Finally got the dealer to change them out. Then I switched to HPS, just soft pedal, but the pads weren't too bad. Then I went to the Stoptechs after fitting them to my M3. I had problems with deposits after bedding, I had to bed them repeatedly, shudder would keep coming back after a while. My M3 occasionally has a shudder, too, but very mild compared to the LGT.

 

I tried the new HPS 5.0 after seeing some good reviews. I took extra care to bed them precisely as the box says, and cool them down with a long drive with no brakes afterwards. No shudder. Rock hard pedal, good bite, little dust. It's been a couple months, I'm happy so far, this is the most firm the pedal in this car has been. I'm not swapping the STi MC on if it stays like this.

 

SS lines did almost nothing for pedal feel, I tried them a few years ago.

 

emosound, interesting experiences.

For me I found the HPS pads were utter crap as well, but more significantly the deposits and spalling were HORRIBLE!!!! Never ever again on this car.

You didn't like the Stoptechs eh? I have not tried any other pads except the HPS, Stoptechs and mystery stockers. The Stoptechs imo with this set up are far superior. They actually feel fairly good (provided you beat on them once a week or so, else they loose bite) and I found no depositing issues with these on stock rotors. Maybe the difference between the HPS and these has clouded my judgement and not allowing me to see beyond, but I am in love with them haha. What are the HPS 5.0s all about? I can definitely go for more bite if these provide

 

Did you find the SS lines helped alot? Curious as to your full review on that before and after.

 

Cheers,

"This car is weird". After years of messing around with the brakes, that is the same conclusion I have come to. I just don't understand some of the behaviors.

 

I have not experienced any shudder, but the rest I concur with. Especially the rebedding on the Stoptechs.

 

So the 5.0s have a totally different feel over the standard HPS? And no deposits? It seems to still be a ferro-carbon. If the new compound it is really that good I may have to give them a try.

 

SS lines would not do much as far as I expect. The problem isn't really a mush, so much as a long pedal travel with pads not biting as they should.

 

The 1" WRX MBC is definitely an improvement over how I had the car set up with Stock +HPS, but it still behaves strangely at times. Often it will feel great, pads will bite, travel will be ok...etc. Other times it feels like the pads hook up like a light switch. Other times again the pads engage right away, but there isn't much bite. Usually some heating helps this a bit, but all of these circumstances occur generally under the same road conditions. Another interesting fact I have noticed is that sometimes the pedal will suddenly relax, as if the power braking system all of a sudden doubles its assistance. Often as the car is dropping to idle (but not from a hard boost situation - engine should be under vacuum the whole time). Recently I have thought maybe this is from an issue with the check valve, but to be honest I am not sure how to diagnose that properly. I feel the ABS hits ice mode far to quickly too. I really need to watch it or my deceleration will go to shit (running 2014 Pilot super sports).

 

Basically I feel I have made the brakes better over the years, but still every time I get in and drive I wonder what the brakes will feel like, and something may feel off/undesirable. I can't say I am happy, but not sure what else to do.

The 5.0 is a totally different feel. The HPS was an ancient compound, I don't know what's different, but it's a whole other world.

 

I suspect the pedal weirdness is a result of the combination of the recirc valve on the intake and the check valve. I don't have a boost/vac gauge, I'd be curious to see at what vac level the booster starts taking vacuum from the manifold. It must need to be a strong vacuum. The thought has crossed my mind to try an electric-motor driven vacuum pump, but I have nowhere near the time or expertise to do it from scratch.

 

Pretty much everything about this car makes me appreciate my 98 BMW M3 even more. Except the wheel bearings, which I understand are a pain on the BMW, but easy to change on the LGT. OTOH, with the same mileage, the LGT bearings failed, while the M3 bearings are fine. So...

:spin: best update I've done to the lgt yet! Feels like Brembos! Strong early bite and consistent pedal feel!

 

My 5eat brakes on steroids!

I still have a sti booster and mc if anyone wants to make an reasonable offer on it.

Sooo.. Wouldn't the 17/16" master cylinder bolt on to our stock booster? Have we determined which part actually makes the biggest difference?