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STI Master Cyl. and Brake Booster SWAP SUMMARY for LGT


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I got 2 sets of flare nut wrenches. One with a lifetime warranty from Advance Auto that began rounding the nuts within 10 minutes of use. The next set I bought was Craftsman, and that set completed the job. The problem with these wrenches is that they are relatively small and flimsy compared to the torque required to break free the nuts. That vice grip appears to be a much stronger unit that would allow for much more torque before deforming.

 

And the bleeders on my wife's Outlander are 6 or 7mm and I'd rather not have to buy a whole additional set when one tool would work for all.

Edited by spec.B Dream
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I've had good luck with my Craftsman set. I think they go from 8mm up to 12 or 14mm. For the bleeders on the calipers, I've always had good luck with the boxed end of a combo wrench.
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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.

 

Yeah, I'm actually interested in eventually running the GS M/C Brace in conjunction with the STi M/C and Booster. I actually posted in the GS Brace thread but as far as I know no one has tried using the brace with the STi M/C Booster swap. Even the GS guys weren't sure if it would fit. When I do my STi M/C and Booster swap gonna be taking a bunch of pics and measurements so I can compare the location of the M/C swap compared to the stock M/C to determine if the GS brace will fit. I suspect that it will, but there's only 1 way to know for sure...

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  • 1 month later...
Is there any specific model year for the STI MC+BB that works better than another? GD or GR? Or are all the model years the same?

 

 

From my quick search 04-07 STI use the same MBC and booster. But for sure 04-05 will work. I'm picking one up soon to round off my brembo, ss lines and fluid flush.

276hp/347tq On a DynoJet

Dyno Video - Had a big lean spot as you can tell in the second pull

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Well, that's not exactly correct. On the Legacy, the brake check valve is not built inside of the booster. It is external to the booster, but uses a different type of mounting than the STi booster. The LGT check valve is on the end of the hose and is press-fit into a rubber sealing grommet on the booster itself. On the STi Booster, there is a 3/8" Hose connection for the vacuum line. I'll take some pics of both to show what i'm referring to...

 

I'll actually be doing this swap either this week or next and going to take a lot of pictures and measurements and will be writing a DIY Walkthrough of the whole process. I'm not going to use the STi check valve though. I'll be using an inline brake check valve from either a Toyota Supra or Nissan S13 or S14...

 

did the swap yet? kind of wanted to see your DIY walkthrough before I proceed..

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I just put my STI master cylinder/booster in tonight after having it sit on the shelf for over a year. Everything went in without a hitch in my MY08. First impressions are good, there is still a bit of 'nothing happening' at the top of the pedal travel but then once it engages the pedal feel is definitely better, not nearly as mushy as it was before. I think with some good pads (bobcats), SS lines, and some ATE superblue, this would make for much better brakes.

 

It wasn't as dramatic as I was expecting, but then again I just spent the weekend driving my parent's IS350 and '10 acura TL. THOSE things have touchy brakes. I flushed a full quart of new Valvoline DOT 3/4 synthetic fluid in using my vacuum bleeder, I had flushed it out a couple months prior with some crappy Wear Ever fluid and it turned back to mush within a couple months so this was a good time to swap the booster in. I flushed/cleaned the crud out of the master cylinder using the same technique of detaching it from the booster and the reservoir, putting it into a cup filled with brake fluid, and working the piston back and forth a bunch of times to work the dirt out of it. I only had to do it a couple times, there wasn't much coming out. I also did rinse/shake the reservoir out with brake fluid as it had a bit of dirt inside it.

 

A word of warning, if you are doing the bench bleed like I did using rubber vacuum caps to plug the threaded holes for the lines, WEAR SAFETY GLASSES. I was working it back and forth and managed to blow one out of the hole and spray brake fluid all over my face and into my right eye. I washed it out right away with saline a bunch and it is fine, but that is nasty stuff you don't want in your eyes.

 

I did have one thing to add to the whole thread, and that was that I had to "clearance" (read, hit with a hammer and bend over on itself) the back lip on the STI booster to give some more clearance to the hardlines right behind it on the firewall on the left side. I have a couple pictures I will add to this thread to show the differences clearer of the boosters. The shape of the STI booster is more flat on the back and puts part of it closer to the firewall and ran into the lines.

 

For clarity: In the first picture, the STI booster/BMC is on the left. In the second picture, it is on the right. In the third picture, you can see where I had to fold the lip over using a hammer on the back side of the booster, from approximately 1-o'clock to 3-o'clock. This should have zero affect on it's reliability/functioning. You can see how the STI booster will be closer to the firewall.

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Edited by sjwelna
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As a follow up the 'nothing happening' at the top of the pedal travel I am almost sure is 100% the booster. When I had everything apart I could push the rod that bolts to the brake pedal in a little ways before it started to move the rod that pushes on the master cylinder. I wish I knew how to make that takeup less, that would make the brakes even better. The upside of having that bit of travel before the brakes bite is that the brake and gas pedals aren't at really different levels, which means you can still heel-toe without having to really crank your foot into a weird position.

 

-Steve

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did the swap yet? kind of wanted to see your DIY walkthrough before I proceed..

 

Unfortunately I haven't gotten a chance to do it yet. Just haven't had the time. Was actually gonna try to do the swap this past weekend, but completely forgot to bring my brake bleeder home from work on friday. :mad:Maybe i'll get to squeeze it in next weekend...

 

sjwelna...thanks for the post and pics. Great comparison of the two boosters...was planning on taking some similar pics when I did mine. From your pics it looks like the STi booster and M/C combo might be a little shorter than the LGT booster/MC. Is that the case or is it just the angle of the boosters, etc in the pics? Just trying to deduce whether the GrimmSpeed MC Brace will work with the STi Setup.

 

As a follow up the 'nothing happening' at the top of the pedal travel I am almost sure is 100% the booster. When I had everything apart I could push the rod that bolts to the brake pedal in a little ways before it started to move the rod that pushes on the master cylinder. I wish I knew how to make that takeup less, that would make the brakes even better. The upside of having that bit of travel before the brakes bite is that the brake and gas pedals aren't at really different levels, which means you can still heel-toe without having to really crank your foot into a weird position.

 

I'm wondering if lengthening the pedal rod on the booster a little bit from the recommended length might work to reduce that pedal travel, however I know from the other STi Booster/MC thread that some people that didn't adjust that rod to proper length have had issues with the brakes locking up after a period of driving. Was probably enough to be constantly sightly applying the brakes causing them to overheat. Hmm...might play with that length a little when I do mine...

One last thing...any chance you got to check if the LGT fluid reservoir would fit onto the STi Master Cylinder? My '06 STi Master Cylinder didn't come with a reservoir and i'm wondering if I can just swap the LGT reservoir onto the STi Master Cylinder. The spacing of the ports looks pretty close between the two but haven't gotten to actually take any hard measurements or actually try fitting it. Anyway, thanks again for the pics.

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As mentioned in the other thread, the take up is easily adjusted by turning the cleavis. If you would like to remove the take up, try turning the cleavis a half turn at a time. I like alittle take up.
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I posted this in the other thread, but the brake pedal free play is very minimal, 2-3mm so it isn't that. (tested by pumping up the pedal until totally firm, then pushing on the brake pedal with 2 fingers lightly to check how far it will still travel, it will move about 2-3mm until it hits the first stop point, then you have to push really firm to get it to move a little bit more, still the total travel is minimal)

 

Also, after driving around with the new booster in, it really does firm up the pedal. There isn't a lot of nothing at the top of the pedal now that I've given it some time, I had to do the first test drive in the rain so that could have been contributing (wet rotors?) Overall I'm very happy. :)

 

-Steve

Edited by sjwelna
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I just put my STI master cylinder/booster in tonight after having it sit on the shelf for over a year. Everything went in without a hitch in my MY08.

 

Wait. Don't 08's have VDC? Did you have to reflair or change the ends the hard lines going to to the ABS brick on the other side of the car? What year were your STi parts?

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Wait. Don't 08's have VDC? Did you have to reflair or change the ends the hard lines going to to the ABS brick on the other side of the car? What year were your STi parts?

 

I'm pretty sure my car must have been an early-year production of the MY08. I checked my hardlines before I bought/installed the MBC/booster and they were the correct size, 10mm. My car also didn't have the stretchbelt that is supposedly part of this model year as well, I had the tensioner so I didn't need all the Gates parts from Grimmspeed. :confused:

 

-Steve

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I'm pretty sure my car must have been an early-year production of the MY08. I checked my hardlines before I bought/installed the MBC/booster and they were the correct size, 10mm. My car also didn't have the stretchbelt that is supposedly part of this model year as well, I had the tensioner so I didn't need all the Gates parts from Grimmspeed. :confused:

 

-Steve

 

I from cars101, the cutover was in roughly July 07. Know what your build date was?

 

EDIT: I went and checked my MBC, 12mm. at the booster and the ABS controller. Damn.

Edited by HtA77
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