Anybody know where I can find the table comparing "swept area" for Wrx front calipers of various years? I have '02 WRX calipers on front of my 818S, need to decide which calipers to use to improve rear beaking.
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Anybody know where I can find the table comparing "swept area" for Wrx front calipers of various years? I have '02 WRX calipers on front of my 818S, need to decide which calipers to use to improve rear beaking.
Is the Legacy GT front caliper larger than my current '02 WRX front rotor? I already have H6 rotors in rear of my 818, I would like to be able to use them.
This is what is in the service manual:
Last edited by Bob_n_Cincy; 04-18-2019 at 02:41 AM.
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Isn't there a difference in size/swept area in various WRX brake caliper models 2002-2008?
From the rockauto page, it looks like the same rotor was used from 2002-2010
brakess.jpg
818S #22 Candy Blue Frame, Front Gas Tank, 2.5L Turbo, Rear radiator, Shortened Transmission, Wookiee Compatible, Console mounted MR2 Shifter, Custom ECU panel, AWIC soon
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What about the diff. in piston area between 2 pot and 4 pot front calipers?
The impreza 2 piston sliding caliper has 1.685 diameter piston. Which is 2.230 square inches times 2 is 4.460 square inches.
The master cylinder is 1.0625" diameter piston. Which is 0.887 square inches.
Master cylinder to caliper squeeze gain is 4.460/0.887 = 5.030
The wrx 4 piston fixed caliper has 1.591 diameter piston. Which is 1.988 square inches times 2 is 3.976 square inches.
The master cylinder is 1.0" diameter piston. Which is 0.785 square inches.
Master cylinder to caliper squeeze gain is 3.976/0.785 = 5.062
As you can see the caliper squeeze force gain is very close between an impreza and impreza WRX.
Bob
Last edited by Bob_n_Cincy; 04-19-2019 at 12:19 PM.
818S #22 Candy Blue Frame, Front Gas Tank, 2.5L Turbo, Rear radiator, Shortened Transmission, Wookiee Compatible, Console mounted MR2 Shifter, Custom ECU panel, AWIC soon
My Son Michael's Turbo ICE Build X22 http://thefactoryfiveforum.com/showt...rts-818S-Build
My Electric Supercar Build X21 (on hold until winter) http://thefactoryfiveforum.com/showt...e-Build-Thread
On the 4 piston caliper, isn't the math 4 times the 1.98 square inches?
No, but it's hard for me to explain.
On a 4 pot system, 1/2 is the applied force and 1/2 is used as reaction force.
On a 2 pot system the pots are the applied force. The back side of the pots push the sliding caliper resulting in that reaction force being applied to the outside pad.
Bob
818S #22 Candy Blue Frame, Front Gas Tank, 2.5L Turbo, Rear radiator, Shortened Transmission, Wookiee Compatible, Console mounted MR2 Shifter, Custom ECU panel, AWIC soon
My Son Michael's Turbo ICE Build X22 http://thefactoryfiveforum.com/showt...rts-818S-Build
My Electric Supercar Build X21 (on hold until winter) http://thefactoryfiveforum.com/showt...e-Build-Thread
I have the same as 20boxer except I am running the DBA rear rotors. Just to be clear, we are running the 2 pot sliding front calipers on all four corners. I have run about a dozen track days with no problem with any brake fade. This setup gives me 150% of braking capacity over standard Impreza with a car that weighs about 60% of a standard Impreza. I am using some Powerstop street performance pads. The have plenty of grip but do emit a lot of brake dust. https://www.powerstop.com/product/power-stop-z26/
Last edited by Bob_n_Cincy; 04-20-2019 at 08:34 PM.
818S #22 Candy Blue Frame, Front Gas Tank, 2.5L Turbo, Rear radiator, Shortened Transmission, Wookiee Compatible, Console mounted MR2 Shifter, Custom ECU panel, AWIC soon
My Son Michael's Turbo ICE Build X22 http://thefactoryfiveforum.com/showt...rts-818S-Build
My Electric Supercar Build X21 (on hold until winter) http://thefactoryfiveforum.com/showt...e-Build-Thread
I will be ordering a pair of two pot front calipers to use in the rear over the H6 rotors that I already have. I know that I will have to re-drill the mounting holes in the rear backing plates and use spacers in the rear calipers to avoid having the pistons run out of travel. I will also trim some friction material from the outside of the rear brake pads so they don't overlap the outer edge of the H6 rotor. Anything else?
Here is a picture of that setup. Notice how there is room for bigger rotors. IMG_20141013_173428719_HDRs.jpg
818S #22 Candy Blue Frame, Front Gas Tank, 2.5L Turbo, Rear radiator, Shortened Transmission, Wookiee Compatible, Console mounted MR2 Shifter, Custom ECU panel, AWIC soon
My Son Michael's Turbo ICE Build X22 http://thefactoryfiveforum.com/showt...rts-818S-Build
My Electric Supercar Build X21 (on hold until winter) http://thefactoryfiveforum.com/showt...e-Build-Thread
The rotors in your pic. don't look like my H6 units - yours is vented.
That picture is the first rotor I tried.
https://www.rockauto.com/en/moreinfo...=1435927&jsn=1
it was used on IMPREZA 2006-2007 and LEGACY 2005-2009
Below is the picture of my current rear DBA rotors.
brake_DBA.jpg
818S #22 Candy Blue Frame, Front Gas Tank, 2.5L Turbo, Rear radiator, Shortened Transmission, Wookiee Compatible, Console mounted MR2 Shifter, Custom ECU panel, AWIC soon
My Son Michael's Turbo ICE Build X22 http://thefactoryfiveforum.com/showt...rts-818S-Build
My Electric Supercar Build X21 (on hold until winter) http://thefactoryfiveforum.com/showt...e-Build-Thread
So the DBA is bigger diameter - does it require modified e-brake shoes?
The DBA 2657 fits Impreza standard 170 mm e-brake and is 316mm diameter and 20 mm thick.
dba_2657_cat_a.jpg
818S #22 Candy Blue Frame, Front Gas Tank, 2.5L Turbo, Rear radiator, Shortened Transmission, Wookiee Compatible, Console mounted MR2 Shifter, Custom ECU panel, AWIC soon
My Son Michael's Turbo ICE Build X22 http://thefactoryfiveforum.com/showt...rts-818S-Build
My Electric Supercar Build X21 (on hold until winter) http://thefactoryfiveforum.com/showt...e-Build-Thread
So the DBA 2657 is bigger diameter than my stock '02 WRX front rotors (276 mm)? Is that going to lock my rear brakes before front?
The portioning valve would be moved to the rear to trim down the backs a bit. This almost unavoidable really. No rear Suby brakes are going to give you the stopping force required for a balanced setup.
The other option vs. the expensive DBA rotors are thicker ebrake shoes (godspeedbrakes in the UK sells them), and standard '04 STI rear rotors (can get blanks for $40/per).