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Old 06-15-2020, 04:23 PM   #1
Chuckable
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Performance Pack Brembo Rear Brakes

If this has already been answered, please point me to the right direction and I will be happy to read up on it. I looked, and didnít find anything, but it wouldnít be the first time I missed something right in front of my face.

I found a set of used but good condition rear Brembo calipers, and as best as I can tell after looking at parts diagrams they will bolt on in place of the factory sliding piston calipers. Obviously, the brake lines, brake pads, etc. are different, but I was under the impression that they bolt on and work without any brackets or need for a different master cylinder or anything else.

Is that assumption correct? Thanks!


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Old 06-15-2020, 04:49 PM   #2
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It is, but they only properly pair up with PP front brembos, and nothing else.
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Old 06-15-2020, 04:56 PM   #3
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As Mike said, they will " bolt on" in the sense that they fit, but they will disturb your brake bias in a negative way.
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Old 06-15-2020, 05:09 PM   #4
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Performance Pack Brembo Rear Brakes

I have the Stoptech ST40 calipers with 328x28mm rotors. From what Iíve read, the brake bias is compatible, but Iím not sure?


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Old 06-15-2020, 06:22 PM   #5
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I have the Stoptech ST40 calipers with 328x28mm rotors. From what Iíve read, the brake bias is compatible, but Iím not sure?


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You *can*, but it will affect your biasing and hurt stopping distances.
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Old 06-15-2020, 06:26 PM   #6
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Thank you, CSG. I just called Stoptech and they confirmed that the setup is compatible. They also said any change in brake bias will be very slight. I guess I need to do some more research.


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Old 06-15-2020, 06:36 PM   #7
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@CSG Mike, would you be able to share the data that led to your conclusion?


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Old 06-15-2020, 06:44 PM   #8
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Thank you, CSG. I just called Stoptech and they confirmed that the setup is compatible. They also said any change in brake bias will be very slight. I guess I need to do some more research.


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a 1.5% shift in bias may seem like very little, given that it's a small number, but a 1.5% shift in bias in a typical car means your stopping distance is going to be hurt by ~10%.

10% may not seem like a lot, but lets say you slam on the brakes at 65mph to avoid hitting the car that just shot out in front of you and now you're trying to not t-bone them. Lets also assume that you're a professional, and you can threshold brake at 100% of the limit of your braking system. That 1.5% shift in bias compounds into the difference between stopping just in time with your bumper ever so slightly grazing them with no real damage, versus slamming into them at 7.5mph, and totalling two modern cars.
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Old 06-15-2020, 06:45 PM   #9
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@CSG Mike, would you be able to share the data that led to your conclusion?


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piston size * radius of rear PP Brembo, vs piston size * radius of base model.

I don't have the exact numbers as I did the math years ago, but the deviation was north of 14%. It's just a simple ratio, disregarding caliper stiffness and pad compound.

If a kit is made for the base model rear, it never works with the PP Brembo rear, on this platform. Likewise, the PP Brembo front never works with the base model rear, or any other rear, on this platform.
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Old 06-16-2020, 12:16 AM   #10
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Performance Pack Brembo Rear Brakes

Thank you to CSG.

This article says that the Stoptech ST40 setup on the front with OEM rear single piston calipers move brake bias rearward by 0.86%: https://www.pointmeby.com/2016/09/24...z-frs-gt86-86/



With that in mind, I did some research and find the following piston sizes for the different caliper setups:

OEM front Brembos:
40mm x 4 pistons

Stoptech ST40 front:
34mm x 2 pistons
40mm x 2 pistons

Stock rear sliding calipers:
40.5mm x 1 piston (though the above chart lists it at 38.1mm which conflicts with other sources and may undermine the calculations in that article if the wrong rear piston size was used)

OEM rear Brembo:
40mm x 2 pistons

@CSG Mike, when you wrote the above estimate about brake bias (1.5%) I took it to mean you were basing it off a stock front 2-piston sliding caliper coupled with the OEM Brembo rear calipers. Is that a correct assumption?

I used an online calculator and came up with the following:







Do any of these calculations look close? If so, then it appears that the Stoptech front with Brembo rear is 0.031% different than the stock all Brembo performance pack setup. Math was never my strongest subject, though.

Thanks for all your help!

Last edited by Chuckable; 06-16-2020 at 01:01 AM.
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Old 06-16-2020, 02:59 AM   #11
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The math is sound; I'll have to check on the actual numbers via measurements!

However, logically speaking, as you can see, Brembo front base rear has a different bias from Brembo front/rear. Therefore, the stoptech can only match the base rear, or the brembo rear, but not both!
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Old 06-16-2020, 08:08 AM   #12
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Performance Pack Brembo Rear Brakes

Quote:
Originally Posted by CSG Mike View Post
The math is sound; I'll have to check on the actual numbers via measurements!

However, logically speaking, as you can see, Brembo front base rear has a different bias from Brembo front/rear. Therefore, the stoptech can only match the base rear, or the brembo rear, but not both!

Thank you again for your feedback!

I can confirm that the base rear caliper piston is about 40.5 mm. (From a 2017 Toyota 86).


You wrote: ďTherefore, the stoptech can only match the base rear, or the brembo rear, but not both!Ē

Would you mind clarifying what you meant by this? Not sure I understood?


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Old 06-16-2020, 05:28 PM   #13
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Quote:
Originally Posted by Chuckable View Post
Thank you to CSG.

Do any of these calculations look close?
Appreciate this thread as in the future I was considering swapping the Front Brembo's for the AP Sprint kit for weight savings, etc...

Cobalt Friction has drawings of the Brembo and Stock pad shapes. The radial depth #'s don't quite line up with what you have.

Stock front : 50.25mm, 1.978" :
Stock rear : 34mm, 1.337"
Brembo front : 59.35mm, 2.337"
Brembo rear : 47.3mm, 1.860"
Stoptech front : 49.25mm, 1.939"

Is the overall pad height in those drawings the right value to use for "radial height" ?

@CSG Mike : Sounds like the Brembo and stock brake bias percentages are different - which is better for track use in your opinion?

Last edited by 86league; 06-17-2020 at 11:04 AM. Reason: Added Stoptech pad
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Old 06-16-2020, 05:39 PM   #14
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@86league thank you for taking a closer look at the numbers. For the measurements you referenced I just used the default numbers provided by the calculator. With your updates though, we are getting closer to a more accurate calculation that will be useful to us and others in the future.


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