STI Master Cyl. and Brake Booster SWAP SUMMARY for LGT

[Windy Road]

Auto's and the Spec B's have VDC. The 5sp GT for 08-09 have no VDC.

[rpoz28]

I noticed in various parts listings that there's a different part number listed for WRX brake boosters with an automatic vs manual trans. I would assume that the WRX manual and STI boosters are the same. Has anyone with a 5EAT LGT installed an STI booster? I looked through the two threads on the STI booster swap but some folks don't have their trans listed in their info.

[PearlBlueGT]

Would you be able to use perrin brake booster bracket with STI booster on 05GT?

[Scooby2.5]

Well I ordered an 06 STI master cylinder and booster from ebay today and ordered the hose from my local dealer.

 

I have the Brakeswap Wilwood kit on my car and it has the mushy pedal feel to it.

 

Ill let you know how it turns out in a week or so.

 

Putting it on a 2005 Outback XT.

 

I have legacy GT rear brakes, and the Wilwoods up front with DBA4000 rotors and, and Porterfield R4S pads I just put on this week along with Motul RB600 fluid.

 

Hopefully this will cure my mushy pedal.

 

 

Weird thing is a friend of mine put stoptechs on the front of his car and his pedal feels pretty firm.

 

Much more so than mine.

 

I checked the booster and M/C differences between the 05 XT and the 05 GT and they seem to be the same although the numbers were a bit different. The XT did have small 2.5i brakes from the factory.

 

 

Cant wait to see the result and see if this firms the pedal up.

Edited May 22, 2012 by Scooby2.5

[triple_B]

I noticed in various parts listings that there's a different part number listed for WRX brake boosters with an automatic vs manual trans. I would assume that the WRX manual and STI boosters are the same. Has anyone with a 5EAT LGT installed an STI booster? I looked through the two threads on the STI booster swap but some folks don't have their trans listed in their info.

 

 

I too would like to know if there are any differnces for this swap on a 2007 5eat.

why would traction control (VCD) affect the brake booster swap. dont our generation cars all have traction control? the 05-06 just get a button to turn it off, correct?

 

thanks for any info.

Edited May 22, 2012 by triple_B

[Metal2You]

My 2006 5MT does not have traction control. Maybe the automatics do?

[SCHM1AN]

I've got an 06 5EAT and I have TC.

 

it's my right foot.

[triple_B]

^^^^

i have a dog terd:

and its better than that post!

[.blackgt.]

08 Lgt auto with vdc button.

[HtA77]

I too would like to know if there are any differnces for this swap on a 2007 5eat.

why would traction control (VCD) affect the brake booster swap. dont our generation cars all have traction control? the 05-06 just get a button to turn it off, correct?

 

thanks for any info.

 

You can turn of the VDC in the 08 as well; it is just a button.

 

The cars equipped with VDC have a different size flare nut (12mm vs 10mm on non-vdc cars) on the end of the hard lines that run across the engine bay from the master cylinder to the ABS controller/pump. You can either change the nut and re-flare the lines or build an 10mm to 12mm adapter. I Not sure if the hard lines are the same inner diameter on both or not or if the volume change would matter that much.

 

Reflaring is not something you want to get wrong as that would lead to loss of braking ability. But any adapter you build will need flare nuts as well. I believe they are bubble flares but I'm not 100% sure.

 

VDC was standard starting in 2007 on the Spec.B then in 2008 it was standard on Spec.B, 2.5i Limited Autos, GT Autos, and 3.0R after July 2007. It was an option on Manual 2.5i Limited and GTs but I'm not sure if that stared in 2007 or 2008. The easiest way to check is to see what size the flare nuts are on the master cylinder. 12mm = you are engineering something. 10mm = direct swap; afternoon job with the correct parts.

Edited May 23, 2012 by HtA77

[spec.B Dream]

Excellent post! I assume VDC is a fairly calibrated system. I do wonder how the change in volume would impact it. Who will be the first to do this with VDC?

[scoobyscoodle]

The I.D. of the VDC lines is the same. The flares on the lines are double flares.

 

Installing on a VDC car doesn't seem too hard. Just get two adapter fittings, shorten a line, and re-flare the end. Everything else should be the same.

[triple_B]

okay,

so i picked up an 2004 wrx mc and bb. i took one of the flare nuts off the MC and it seems the same size as the nut on my 2007 5eat LGT wagon with NO button (and assumed VDC).

 

would this mean that: i dont have VDC; i cant see the difference between 12mm and 10mm; or my MC takes 10mm nuts or the same as the 04 i picked up?

 

i went to a braks shop that had 12mm female to 10mm male adapter but it looked very large. i will go back with the nut off the wrx MC.

 

but i cant take mine off or i cant drive.

 

 

also, if i do remove my flare nut and try the WRX one could i put mine flare nut (with line still attached) back in the MC and then remove a caliper from the rotor and push the pad in to push fluid back up the line and into the MC resevoir in order to get any air bubbles ouf of the line?

 

thanks for any info

[fenominal]

On a side note, from the two people I met at a local meet today who's done the Grimmspeed Master Cylinder Brace mod, they said it made a tremendous difference in brake feel. They swear by it.

 

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

 

This STI MC/BB upgrade will be next for my wife's OBXT.

Edited June 17, 2012 by fenominal

[triple_B]

THIS MOD IS AWESOME! F BBK's and their price tag. i track the car oftern and actually use my brakes repeatable at speed and the stock calipers hold up great. its the stock master cylinder that sucks.

 

new feel is instant (1/4"), constant and solid.

 

my 2007 LGT wagon does NOT have VDC. (the abs modual has all wheel brake lines in a row on the top with the two master cyclinder lines on the front. VDC has lines stagared and MC lines on top as well).

 

my stock MC has the same thread size as an 2004 WRX MC (10mmx1.0) i got from B&R Auto Wrecking for $55 without the check valve which i got at the dealer.

 

i did not take off my AVO TMIC

 

cleaned and painetd used MC then bench bleed it to clean the cylinder.

 

i took off my fuel lines at the firewall. (may not need to do this, i did cause i have the tool and its easy and gave me room)

 

i seperated the MC from the boosters before removal/install.

 

i loosened the small AC line along the frame and the top of the fire wall for wiggle room

 

i measured the threaded rod of the new booster and it is different than my stock. so when i set the new i i just took off the ubolt that goes around the brake pedal arm. this made it easier to install the booster into the car. my brake pedal arm was 1/16" from topped out against the brake light switch.

 

to install the booster i placed it in perpandicular to its final orientation then rotaed clockwise and slid the threaded rod into the firewall hole.

 

thread on the ubolt retainer and set the height of your brake pedal.then

i bolted the booster in place and bolt the MC onto the booster.

 

i again blead the the MC onthe car by putting a bag over teh MC and having wife push pedal and you plug the holes as she lifts off the pedal.

 

put my lines back on and put 600ml of fluid through the system in 2 stages. furthest to closest then closest to furthest; per the manual.

 

Good luck

[scoobyscoodle]

^It is a great mod, but don't forget, although the bore of the sti mc is larger, the sti bb also helps as well.

[Scooby2.5]

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

 

This STI MC/BB upgrade will be next for my wife's OBXT.

 

I have an extra one ill pm you my cell number and call me.

[maniaxzero]

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

 

This STI MC/BB upgrade will be next for my wife's OBXT.

 

Thanks for letting us know the Grimmspeed MCB just wouldn't cut it. BTW, how did you become an automotive journalist? Sounds interesting

[Swine]

Ive been fighting the, "the GS master cylinder fixes my terrible brakes" pill for a while.

 

Its insane how...uneducated and possibly clueless some people can be.

 

Glad to the light is finally start to shine on the source of the problem for more people now.

 

If i owned a stock LGT and i still hated my brake feel, i would do exactly 3 things at once and enjoy much improved feel.

-booster and master change

-pad change

-and you have to flush your fluid when you change the master anyways, so that as well.

 

Its that simple.

[SBT]

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

 

This STI MC/BB upgrade will be next for my wife's OBXT.

 

You did all of that and didn't flush the brake system after installing the SS lines? Your symptoms sound more fluid-related than hardware-related. A flush (or reflush if you did it) will likely help. Especially if it was bled incorrectly - LGT/OBXTs are different than Impreza/STI setups. (Per FSM: Perform the operation in order from the closest wheel cylinder to the master cylinder.)

 

Even flushing with fresh Subaru OEM fluid (now on ATE Blue) really tightened up the whole brake system. Adding the Hawk HPS and the GS MCB really brought the system to 8-9/10ths of a BBK. Stops are definitely much more "right-now" than even I thought possible.

Edited June 18, 2012 by SBT
corrected spelling and added brake bleeding directions from the FSM

[Swine]

His symptoms are what everyone experiences in LGT's who knows what a real brake pedal feels like.

 

His experiences mirror my own, no amount of any aftermarket add on is going to fix the core issue of a Master and BB that was designed poorly.

 

 

Everyone who has swapped to a new master and BB can confirm, everyone who has not still think its a pad and fluid issue.

Edited June 18, 2012 by Swine

[SBT]

- Sorry - Having driven some really sophisticated cars (including some really great-braking Porsche Carreras and BMW M series), the LGT is pretty decent. Pads and fluids get you much further than you're intimating above and the MCB really adds to that. Not discounting that the MC and BB gets you the extra 10%, but having driven an STI and my LGT B-to-B, I don't see that much of an improvement in pedal feel, the Brembos notwithstanding.

[Swine]

- Sorry - Having driven some really sophisticated cars (including some really great-braking Porsche Carreras and BMW M series), the LGT is pretty decent. Pads and fluids get you much further than you're intimating above and the MCB really adds to that. Not discounting that the MC and BB gets you the extra 10%, but having driven an STI and my LGT B-to-B, I don't see that much of an improvement in pedal feel, the Brembos notwithstanding.

 

Sorry SBT, but unless you have an LGT that is an outlier for some reason, you are flat out incorrect. The results of the people on this board clearly indicate an issue with the OEM LGT braking system. My problems and results mirrored their own

 

 

That fact that you have driven sophisticated cars does not mean much to me, or anyone else. What you can do is explain to me what you think makes a good brake pedal feel, and why you believe your LGT has it.

 

 

Quite frankly from the statements you have made so far, im not so sure you understand how brakes work at all, or perhaps their dynamics. Im surely not an engineer, but i do understand some basics below. Feel free to correct or address, please keep in mind im referring to a "normally" operating brake system in non extreme circumstances.

 

1)All brakes use hydraulic brake fluid. This fluid is not appreciably compressible, regardless of brand or make.

2)The only time you get real compression in your hydraulic brake fluid is after air is trapped in the system and the bubbles themselves are compressing.

3)So changing or flushing fluid, unless air is present, will have no change in A)Pedal feel or B)Pedal take up. A)No change in pedal feel. Why? Because regardless of what fluid you run, there is no compression in your brake fluid unless air and/or contaminates are present. B)Pedal take up not improving. Why? Because when you actuate your brakes, thanks to your Mastercylinder and Booster, the same amount of fluid is still pushed through your brake lines. What does this mean?? This means the brake pads move the exact same distance they did previously. So if your pedal take up sucked then, then its going to suck now.

 

Since you also mentioned Pads, of course pads are going to improve pedal feel and bite once the pads are actually engaged and contacting the rotors. OUR problem is the massive pedal take up and pedal slop before the brake pads actually engage.

 

So if the pedal slop and take up is still a problem after most of us have done the pad and fluid change, whats left? Simple, alter the amount of fluid being compressed to the brake calipers in relation to pedal stroke. With the STI Master and Booster, you get more fluid movement with less pedal actuation.

 

Have owned 2 prior STI's, it literally feels like my old trusty Brembo's are back underneath my brake pedal. Take up is immediate, pedal is firm, power is nicely linear, communication is mediocre but that is likely a function of my Stoptech pads more then anything else. These rating were all poor in OEM form, and improved only slightly with a pad change and fluid flush.

 

If you are going for brake feel

-Master and Booster 70%

-Pads 15%

-Fluid change 15%

 

For others reading this, changing just your master and booster will completely change your braking dynamics. It WILL NOT improve braking performance or fade. Once the pads have made contact with the rotors, its all up to the pads and fluid to handle the heat(as far as the dynamic side of the braking equation, you still have the static side including but not limited to your rotors and airflow for cooling).

Edited June 19, 2012 by Swine

[fenominal]

You did all of that and didn't flush the brake system after installing the SS lines? Your symptoms sound more fluid-related than hardware-related. A flush (or reflush if you did it) will likely help. Especially if it was bled incorrectly - LGT/OBXTs are different than Impreza/STI setups. (Per FSM: Perform the operation in order from the closest wheel cylinder to the master cylinder.)

 

Even flushing with fresh Subaru OEM fluid (now on ATE Blue) really tightened up the whole brake system. Adding the Hawk HPS and the GS MCB really brought the system to 8-9/10ths of a BBK. Stops are definitely much more "right-now" than even I thought possible.

 

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.

 

I don't know how quote multiple replies, so I apologize for this longwinded reply--and I don't mean to threadjack, so perhaps I'll soon start my own picture thread when I get my OBXT on the LGT suspension. Long story short--I did 5 years active army with the 101st Airborne, got out, graduated with journalism degree in 3.5 years, and I found an autojourno job under the largest car magazine in the country...

 

Back to the brakes, I don't know much about wear. The pads are Stoptech and what I presume are OEM replacement. Do they need a few hundred miles to break in? If not, I'll consider a more enthusiast option at replacement.

[Swine]

I to owned 2 prior WRX's, one being a wagon with the H6 rear upgrade. Ive never felt the need to address the master and booster on any of my other cars.

 

Stoptech street pads are rebranded Axis Ultimates FYI, they are a nice economical option that are quiet and medium dust. Ive tracked mine with out any cooking or major fade. Best value based aftermarket pad, but there are certainly higher performing aftermarket pads.