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Old 09-15-2020, 09:23 PM   #15
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Quote:
Originally Posted by gtpvette View Post
Andrew,,, any chance you post the correct numbers?? These are the numbers (42.8 and 38.1) I see in most post. I recall seeing a post where a guy had a picture of the pistons with the digital caliper on it,, dam if I can find it today.
In post #10:

Front:
Hitachi CL25VD Caliper with Dual 40.4mm Pistons (1.591 in.) x 2
FA300 Pad Material with 48.3 cm^2 pad area (7.487 in.^2)
294.0 mm x 24.0 mm Ventilated Rotors (11.575 in. x 0.945 in.)

Rear:
Hitachi CLA12V Caliper with Single 40.46mm Piston (1.593 in.)
FN360 Pad Material with 23.0 cm^2 pad area (3.565 in.^2)
290.0 mm x 18.0 mm Ventilated Rotors (11.417 in. x 0.709 in.)

- Andrew
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Old 09-16-2020, 09:36 AM   #16
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Quote:
Originally Posted by 86league View Post
I measured a stock 2016 piston as 40.4mm (granted with a cheap HF caliper, but it's been pretty accurate). Didn't measure the rear (only rebuilt the fronts), but the subaru parts catalog shows the rear caliper using the same part # for the piston as the front -- just 1 rear vs 2 front...

https://www.ft86club.com/forums/show...1&postcount=16


That was the picture I was looking for,, thanks!!!








Quote:
Originally Posted by Racecomp Engineering View Post
In post #10:

Front:
Hitachi CL25VD Caliper with Dual 40.4mm Pistons (1.591 in.) x 2
FA300 Pad Material with 48.3 cm^2 pad area (7.487 in.^2)
294.0 mm x 24.0 mm Ventilated Rotors (11.575 in. x 0.945 in.)

Rear:
Hitachi CLA12V Caliper with Single 40.46mm Piston (1.593 in.)
FN360 Pad Material with 23.0 cm^2 pad area (3.565 in.^2)
290.0 mm x 18.0 mm Ventilated Rotors (11.417 in. x 0.709 in.)

- Andrew

Thanks you sir!
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Old 11-21-2020, 09:14 PM   #17
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Originally Posted by Racecomp Engineering View Post
For pistons I had 42.8 mm for BRZ front and 38.1 rear non-PP USDM calipers...and after all these years it turns out I was wrong. Those numbers still come up most places you look but I think they're wrong now.

So front FHI 4 pot is same rotor and about the same piston area as OEM BRZ (40.4mm), but the rear FHI 2 pot has smaller pistons than OEM BRZ (38.1 vs. 40.46). So a frontward shift with the front and rear FHI set up due to the rear calipers.

Damn it. I'm embarassed. Gonna go back and edit like 50 posts.



- Andrew
Sorry for the bump on an old thread but just to make sure I am understanding correctly. We should be able to use the front FHI 4 pot calipers (off 06/07 wrx) with no changes to the brake bias at all, correct?
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Old 11-21-2020, 10:43 PM   #18
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So would this be an okay OE+ upgrade? It should be a stiffer caliper right?
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Old 11-22-2020, 01:14 PM   #19
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Originally Posted by Bach415 View Post
Sorry for the bump on an old thread but just to make sure I am understanding correctly. We should be able to use the front FHI 4 pot calipers (off 06/07 wrx) with no changes to the brake bias at all, correct?
Minimal if any change to brake bias with just the front calipers.

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Originally Posted by Jdmjunkie View Post
So would this be an okay OE+ upgrade? It should be a stiffer caliper right?
It would be okay. Stiffer caliper and a tiny bit lighter.

- Andrew
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Old 11-22-2020, 02:06 PM   #20
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Originally Posted by Racecomp Engineering View Post
It would be okay. Stiffer caliper and a tiny bit lighter.

- Andrew
How far forward would adding the complementing rear brakes shift the balance forward? How detrimental if at all would the balance shift be and why?
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Old 11-22-2020, 03:12 PM   #21
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The 4-pots make slightly more brake torque (about 6%), while the 2-pot rears have slightly less (~9%).

My numbers are
65.3/34.7 %f/r for the stock brakes
66.6/33.4 with just 4-pot fronts
68.7/31.3 with 4/2 pots

There are a lot of factors that might make a bias change an improvement, or not. Put on stickier tires, and you have the ability to transfer more weight to the front. Lower the car, and less weight is transferred for a given braking rate. Do both, and maybe it cancels out? Addtionally, EBD and ABS are there to try and sort things out.

Last edited by jamal; 11-24-2020 at 03:44 PM.
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Old 11-22-2020, 07:33 PM   #22
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I would just stick with stock till you need better brakes. Better pads/fluid. CSG has great pads for our stock brakes that work really well!

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Old 11-27-2020, 08:12 PM   #23
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^^^This. I am not overly impressed with the 4pots on my WRX.
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Old 12-01-2020, 11:55 PM   #24
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As a few others have pointed out the OEM calipers are pretty good. Just need better pads and fluid for track duty.

I only went up to AP sprints for the heat dissipation and thicker pads that last longer and are usually cheaper or same price, but longer life, than the OEM front pads due to a common size and being thicker
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