Truth about using STI Brembos on the twins
 

Very good read. Calipers are not just calipers.

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

What is interesting is the fact people saying the change in brake bias in actually good. I also feel Brembo has a big reason to tell people they can't be used. As in the $3k starting price of the brake kits.

I've always been weary of doing a swap like that, apparently for good reason.

Only problem is: of course Brembo is going to say you can't make the swap work, they want you to buy their BBKs.

While I agree that they might be trying to steer people to their BBKs, I wonder if this is a valid concern:

Can anyone confirm that the crossover is in fact higher than the relocated bleed screw?

Sent from my XT1095

Somebody should do a test to settle this. Just take three twins, mount one with the a similar Brembo BBK, one with STi, and one stock. Beat the crap out of them with different tests.

I've run mine with the staggered pistons orientated "upside down" and there's hardly any uneven pad wear after approx 7500miles (street use, no track work) so far.

It seems all of the people in the know, ie the guys that are tracking/racing or building cars for that purpose, agree that the STi swap is not an upgrade in performance. Brakes are important. Please don't fuck them up in an attempt to look cool.

As someone that's swapped STI brembos over to a twin, I can confirm a few things:

I didn't die in a fireball (knock on wood)
There is no noticeable decrease in braking performance (as some of stated elsewhere)

I did not invert my bleeders because I could honestly care less about the pads wearing a little unevenly. Even if significant uneven wear were true (which some have proven otherwise), I don't really care if I have to replace my pads a little earlier.

In regular day to day street driving, and the odd "spirited" drive, there is no noticeable difference in bias. I'm going to the local track in May for the first real test on this braking setup, and will report back then. I only really hot lap, so I'm not out for any time attack records. If I were fighting for tenths of a second per lap, I would of just went with an AP Racing setup. With that being said, I don't anticipate any noticeable decrease in performance from my old pad/rotor upgrade on the OEM calipers. The increase in rotor size will also help with heat capacity.

Thanks for posting the article, and although I don't doubt the data in it at all, I can't help but feel that the delivery was skewed to be a bit of a marketing ploy. I realize the science behind why an STI Brembo isn't the #1 choice for a performance upgrade, I don't think i'ts the worst thing you could do to your car either.

Mildly off topic, but since they mentioned the Brembo kits.

Does anyone know if the 4-piston 332x32 front kit will fit under 17" OEM wheels?

http://www.racetechnologies.com/imag...8CE1656666.jpg
http://www.racetechnologies.com/imag...554067E2C7.jpg

AP Racing Factory kit is 330x28, which gives me alot of hope for this. I'm a fan of "better not bigger" brake kits, since I've got 2 sets of 17x7's (OEM & RPF1).

You sure about that ?

No.
Supposedly it is the incorrect staggering of the pistons that lead to uneven pad wear.

Yup, from running the calipers on the opposite side due to not swapping the bleeders :)

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.

Truth about using STI Brembos on the twins
 

You guys are really intent on showing people they're wrong.

I did not invert the bleeders and ran the calipers on opposite sides to compensate.

Ffs this forum is annoying sometimes. People are more interested in proving others wrong than they are contributing to a discussion. Seriously, look at the amount of text has been written to show that I'm dumb for not knowing what I'm talking about. I'll bet I'm the only one of the three of us who has done the swap.

And for clarity: I ran calipers on opposite sides and inverted therefore have inverted pistons. I did this because I wanted bleeders on top but did not swap them.

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

(Front bias)^-1

For street use I'd say there's negligible uneven wear, as I've noticed on mine. I did however notice slight increase in front bias, but fitting rear pads with a little more bite took care of that.

Perhaps with regular track work you'll see accelerated uneven wear, but then flipping the pads from inside to outside should balance it out. Having said that, these brembo's aren't ideal for regular track work anyways.

My personal take... Mine were mounted upside down to keep the pistons correct, and I bled the calipers pointed up, unmounted.

I have been running Front and Rear 13' STI Brembos on my FRS. I started off running Stoptech Posi-quiets in the front and stoptech Street Performance in the rear.(because of the aforementioned bias from other people) I had no plans to track the car when I put the brakes on, and the pad choice reflects that.

I now have 5 track days on this setup. Off the bat I noticed more braking force and better pedal feel, however with that pad setup, I cooked them quickly. I could usually get 3 maybe 4 good laps until I had extreme fade. I only noticed the bias difference when braking hard and consistent from 100+. This setup for the street was perfect.

Last track day I switched out to Winmax W4's front and rear. I was running at Laguna Seca, which is notoriously hard on brakes. The brake bias difference was IMMENSE. I had tons and tons of braking power and consistency(which I attribute mostly to the pads)but the front was so much stronger that the rear would actually dance around on hard braking. I will be switching back to the stock rear setup soon, and test that as well.

I don't plan to have this setup for much longer, as I get more and more into tracking the car. It will be replaced with something actually designed for this car.

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.

Maybe,just maybe, it isn't so much as wanting to prove people wrong but to stop incorrect information being perpetuated.

In this case it would seem that there is negligible difference in having "incorrect" piston stagger but maybe with a different car fitting different model calipers would be disastrous. Where do you draw the line of when to correct?

Have you done the swap?

Now that I have more time...


1) After looking at pictures of split brembo calipers, the crossover indeed is above the bleeders.


2) This may or may not be a problem.


3) It still doesn't explain why there is a blocked bleeder fitting.


4) One could probably get around this by installing an external crossover.


5) Tapered pistons could be up there with crossdrilled rotors on the marketing scale. There's some that say it's bullshit in other words...


Anyway, until someone gets some measurements from the tS brakes, though jp says you have to run 18" wheels to clear them...

The calipers on the BRZ tS is identical to those found on other STi models, meaning they will 100% clear 17" wheels (with correct offset).

I'm no expert, but the posi-quiets wouldn't really be suitable on track. Perhaps keep the W4 rear pads but change to W2/3 fronts with better fluid, and give that a try before you swap back to stock rear calipers?

I have also purchased GDB Brembo calipers but I have not don't the swap.

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They aren't suitable at all for the track, that's why I removed them. I'm not really interested in band-aiding the bias issue. I'm running what is considered to be "great" fluid, and am not having any issues with fade or overheating, just bias. To be honest, the whole setup might come off a all at once if I can find something else I like.

I know stop tech changes the size of their Pistons for each kit. The same st-40 caliper for the sti, m3, vette and brz all have different sized front and rear Pistons. That is, inside the 4 pot caliper, the leading edge piston is a different size than the trailing edge for every model. If a small outfit like stoptech does this, I'm positive subaru, brembo and sti do this as well.

I don't doubt that some part numbers for some bbk's have different piston sizes depending on the application - the reason I said that I refuse to believe that they had a brembo made specifically for the tS is because some if not most of the parts on the BRZ tS were literally pulled out of bins and slapped on the car.

Unfortunately we'll never know for sure unless someone has the part number or measurements of the pistons for the tS brembos. :(

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

Pat

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 :iono:. 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".

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

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.

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

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*.

http://car.watch.impress.co.jp/img/c...625/054/12.jpg

http://car.watch.impress.co.jp/img/c...625/054/13.jpg

Thank you for the clarification. If only we knew the piston sizes!!! :mad0260:

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.

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.........

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?