Truth about using STI Brembos on the twins

[fasteddy]

I would take Brembo at their word about this seeing as they designed the WRX STI calipers.

Pat

[wparsons]

Originally Posted by mikeTee

The second statement from the article about the piston size being incorrect for the FRS/BRZ is bullsh*t because the BRZ tS in Japan comes with the exact same Brembo set up as the WRX STI - 4 piston front, 2 piston rear - though I can't know for sure what the size of the pistons themselves are, IMO the possible difference could only be marginal.

That article is talking about just swapping fronts. if you swap matching rears the bias won't be affected. Incorrect piston sizes will change how the pedal feels and how much travel you need though.

[Fizz]

Originally Posted by wparsons

That article is talking about just swapping fronts. if you swap matching rears the bias won't be affected. Incorrect piston sizes will change how the pedal feels and how much travel you need though.

Actually IIRC if you swap the rears to Brembo as well, the front bias will be even greater compared to just using our stock rears. This is apparently due to the rear brembo piston being smaller than that stockers . But the rear brembo's will gain more "torque" (i think that's the right term?) due to the larger rotors. It all gets very technical and mathematical when you compare on paper.

But what I do know for sure is that my front + rear brembo setup behaves no differently to other WRX STI's that i've driven before. Even a couple of buddies who own STI's commented that my brakes feel very "OEM-like".

[CSG Mike]

Originally Posted by mrk1

Very good read. Calipers are not just calipers.

https://racetechnologies.wordpress.c...or-subaru-brz/

I've been saying that for years... glad Race Tech finally wrote something about it.

[CSG Mike]

Originally Posted by Tbird232ci

He is correct.

The bleeders not being inverted means the air gets trapped in the top of the caliper. Air naturally travels upwards and without the bleeders, it will just stay in the caliper. That will not create uneven pad wear, but it will create a soft and spongy pedal.

The incorrect piston staggering leading to pad wear is all theory. If nothing else, it will only be noticeable towards the end of the life of the pads, If you care enough, you could probably swap the inside pads for the outside pads to even out the wear. Brembos are incredibly easy to swap pads so it really isn't as inconvenient as it sounds.

It's not theory. Street driving only? Sure you'll probably never see uneven wear. Tracking the car with any sort of experience? You absolutely will see uneven wear.

[CSG Mike]

Originally Posted by Poodles

It's kinda comical that they consider more front bias dangerous when the inverse is the truth...

It's about the same as saying that understeer is safer than oversteer. Both have their inherent pros and cons.

[CSG Mike]

Originally Posted by mikeTee

The second statement from the article about the piston size being incorrect for the FRS/BRZ is bullsh*t because the BRZ tS in Japan comes with the exact same Brembo set up as the WRX STI - 4 piston front, 2 piston rear - though I can't know for sure what the size of the pistons themselves are, IMO the possible difference could only be marginal.

The first statement does address the possibility of an issue if the staggered STI Brembos which in the past have used 46mm and 40mm pistons on the front caliper but again I think the size of the pistons and their positions is marginal - and I do believe that Subaru is reusing the same brembos for their WRX STI as the BRZ tS, I refuse to believe that they had a car specific brembo made for the tS but again I could be wrong about this.

Lastly, is there any validity to the statement about not being able to fully bleed out the caliper? I keep on thinking about how brakes are bled out and I don't really see how the air can't all be forced out.

It is indeed car specific, per the Brembo engineers I spoke with. Brembo is very capable of making small runs of calipers sized specific to an application. They're very similar *looking*.

[mikeTee]

Originally Posted by CSG Mike

It is indeed car specific. Brembo is very capable of making small runs of calipers sized specific to an application.

Thank you for the clarification. If only we knew the piston sizes!!!

[CSG Mike]

Originally Posted by fasteddy

I would take Brembo at their word about this seeing as they designed the WRX STI calipers.

Pat

For the record, Race Technologies is to Brembo, as Essex/Stillen are to AP Racing.

Now, Brembo and AP are owned by the same entity (Brembo), but are still competing brands. Technically, AP Racing is a direct competitor to Brembo Racing, which is a separate brand from Brembo.

[WesleyG]

While I do not have the technical know how to prove or disprove the technical reasoning in the article, I cannot help but notice the advertisement in the bottom and the 3k price tag for the upgrade from them.

Hey guys dont use the second hand calipers that fit on your car, because you will die, but instead buy this kit from us.........

[King Tut]

I love this thread. That wordpress "article" is filled with opinions and no facts. They list 30% but don't mention if that is with just swapping the fronts or swapping fronts and rears and with what pad compound front and rear. ABS problems, haha. All ABS cares about is what that wheel speed sensor is telling the ABS computer. You can lock up your brakes and get into ABS with or without the STI calipers. You won't kill yourself if you do the STI swap, and there are plenty of ways to get the air bubbles out with the pistons in proper orientation and the bleeders swapped. Air bubbles can get trapped anywhere in the calipers not just the crossover bar. That is why you are supposed to hit them with a rubber mallet to dislodge the air bubbles to the bleeder location. Brake bias is something that can be adjusted with pad choices or a brake bias adjuster in more track oriented applications.

[CSG Mike]

Originally Posted by King Tut

I love this thread. That wordpress "article" is filled with opinions and no facts. They list 30% but don't mention if that is with just swapping the fronts or swapping fronts and rears and with what pad compound front and rear. ABS problems, haha. All ABS cares about is what that wheel speed sensor is telling the ABS computer. You can lock up your brakes and get into ABS with or without the STI calipers. You won't kill yourself if you do the STI swap, and there are plenty of ways to get the air bubbles out with the pistons in proper orientation and the bleeders swapped. Air bubbles can get trapped anywhere in the calipers not just the crossover bar. That is why you are supposed to hit them with a rubber mallet to dislodge the air bubbles to the bleeder location. Brake bias is something that can be adjusted with pad choices or a brake bias adjuster in more track oriented applications.

While many of those fixes are hacks that do work at a basic level, as you progress as a driver, you'll hit the limitations of the system much faster.

For example, the front bias can be somewhat mitigated with a more aggressive rear compound, but then now the rear is working harder. As the rear heats up faster, the Mu also rises faster (typical with most pads), causing, now, a rear brake bias. As the rear continues to work harder, it heats faster than the front, and then overheats much earlier than it should. Now you only have front brakes.

How would this constantly changing brake bias benefit a newer driver, who is trying to learn to safely drive on track, when the brakes are changing on him in real time?

[Racecomp Engineering]

I would be pretty surprised if the tS BRZ used the same brembos as the STI. The brake bias with the full front and rear kit is pretty awful (as noted by those who have actually tracked the full set-up).

I'm someone who can do math, so in this case it's something that checks out on paper and in the real world. Yes, it's mostly fine on the street and you can shift brake bias in other ways, but I'd much rather just run a proper kit (which in some cases is not a ton of money).

FWIW, the Brembo front and FHI 2006 WRX 2 pot rear combo is better.

- Andrew

[continuecrushing]

Originally Posted by Racecomp Engineering

...

FWIW, the Brembo front and FHI 2006 WRX 2 pot rear combo is better.

- Andrew

better? as in its not recommend, but if you are hell bent on doing a sti brembo swap, its better to do brembo front/wrx rear? Or better to just avoid it all together since they are both "bad" for bias.

I only ask because I was heavily contemplating doing this. My buddy has a full set of the 06 4 pot/2pot calipers for me, but because of the rear brake bias issue of doing the full 4/2 pot swap I haven't done anything with them yet, and I was thinking of doing the sti brembo front, and the 2 pot wrx on the rear.