nauri9

Has anyone ever tried fitting two piston rear calipers to our cars? I have been contemplating this, and aside from not having a e-brake I think it would be awesome and aesthetically pleasing, complementing the four piston fronts.



From the little research I have done on the web 2006+ Subaru WRX rear calipers seem best (11.3" rotor 20mm thick) since they are aluminum and the Subaru badge is just painted on.
also Nissan z32 rear calipers could work (11.75" rotor 30mm thick) and some BMWs come with 2 piston rears.

our rear rotors are 20mm thick and 10.7 inches in diameter so the Subaru caliper seems very close, the only problem would be if the Subaru pads were to tall to fit between the inner and outer diameter of our brake rotors. our pads are 39.4 mm tall.

so can anyone find info on the rear pad height for a 2006 wrx. If it would fit all we would need to do is machine a adapter bracket!

10aeRX7

iTrader: (3)

i beleive there is post of a t2 front caliper on the rear conversion done with 2005 mustang gt rear rotors. i think he put 2 4 pot one as the brake other as hydro e brake

nauri9

I saw that car when I was searching the site for anything like this, personally this would be a lot cleaner and probably have the correct brake bias. also this would only be practical for a track car, and would work well for someone who drifts and has a hydraulic hand brake for the rears.

Evil Aviator

You would be better off spending your time and money on something more worthwhile like DOT SS lines and performance pads. Even mid-level competition RX-7s still use the stock rear calipers, so unless you are building a half million dollar GT race car, there is no point in "upgrading" the rear calipers except for looks. If you do just want the looks, then I would recommend a top name brand like AP, Baer, Brembo, Wilwood, etc., as Subaru would look ghetto IMO. You can save money and just spray paint your stock calipers and put on a ricer decal, or buy ricer covers like this:
http://www.sportsimportsltd.com/reddicaco.html

danegerous

iTrader: (10)

OH MY JESUS @ Those fake caliper covers

nauri9

OUCH! The reason I am contemplating this is because their is no multi piston for the rears that I have found and like I stated before the Subaru emblem is only painted on. also some used calipers would be fairly cheap. I am not a ricer and if I ever get off the concept stage it will go on my BP autocross car.

SoloII///M

iTrader: (13)

There's too much rear brake bias as it is, unless you fitted an adjustable proportioning valve or went to a different master cylinder it would be a nightmare.

nauri9

except for the big balloon tyres (and "Superu" emblem) this is what it would be like.



Someone got creative when painting their calipers.

here is the same application but with after-market calipers

danegerous

iTrader: (10)

Aside from how it looks, like Solo II said the brake bias would be off even more. You'd need to run a bigger M/C from a Mazda 929. It seems like a lot of work for not a lot of gain.

nauri9

In BP stuff like this is just part of the game.

clokker

iTrader: (2)

Master cylinder size has nothing to do with brake bias, the proportioning valve handles the bias.

blindboxx2334

iTrader: (2)

true.. but when you up the pistons shouldnt you also up the brake m/s? but then again. your going from a 1 somewhat decent sized piston to 2 smaller ones. so i dont think it would matter

danegerous

iTrader: (10)

I meant needing the m/c to push the bigger brakes

nauri9

thanks for all the replys, I think the next step is to go down to the parts store and measure the pad size for the Subaru calipers to see if they would work with the stock size rotors. and I also found that a master cylinder from a Subaru outback will work. "The Holy Grail (Part Deux)"

SoloII///M

iTrader: (13)

The pressure change is equal to the ratio of the two surface areas (one piston area vs the two piston area).

Evil Aviator

Beats the heck out of going through a lot of work to replace the rear calipers with shiny ones with no significant advantage over the originals.

If you are going the race in the EM class, then you may as well completely upgrade your brakes. A larger-diameter vented rear rotor should yield better results than simply swapping out the rear calipers. About 10 years ago a lot of guys were using Outlaw calipers as a low-priced upgrade, but I have not been around the track lately to see what the highly-modified RX-7s are currently using.
http://www.outlawdiscbrakes.com/calipers.html

nauri9

The Subaru pads are 35mm at their narrowest so everything looks like it will fit. I have a pair of free calipers on the way to test fitment, though i have to return them or pay for them when I am done testing. Everything is looking good so far.

I cannot say yet what the total piston area is but it appears to be greater than our stock piston, so clamping force would increase. Also this setup will fit in 15 inch rims and my future setup will be 275/35r15 Hoosier a6 on 15x10 rims so I definitely can use the extra braking power.

SoloII///M

iTrader: (13)

I guarantee the stock brakes have enough clamping force to lock up a 275 A6. And on an XP RX-7 (BP no longer exists) you'll be focusing on weight savings. i.e. run the smallest diameter rotor you can with the lightest caliper.

fc323

this is cool. if its works im down to put that on my rx7
keep this updated!

Aaron Cake

iTrader: (1)

Pretty sure that this unnecessary brake upgrade will bump you right out of BP. Or is BP even a class anymore?

The rears do such little compared to the fronts that through the entire 2nd and 3rd gen model runs of RX-7, Mazda didn't see the need to upgrade them. Even though there were putting MASSIVE and EXOTIC (for the day) 4 piston calipers up front.

Take some bias OUT of the existing rear calipers and you will find the car a little more predictable.

clokker

iTrader: (2)

"Massive", OK, "exotic"...not so much.
A very popular upgrade to the Datsun Z cars was the 4-piston calipers off a four wheel drive Toyota pick up truck.
(Coincidentally, a Subaru limited slip diff was also a direct bolt in swap...life was pretty easy in Z-world...).

Aaron Cake

iTrader: (1)

Were they aluminium? But that's a pickup, not a passenger car. There are huge brakes on a Ford Excusion but one can't make the comparison.

blindboxx2334

iTrader: (2)

i seriously hope your kidding. i had a 78 280. they didnt make any parts for it and the ones they did they were expensive as hell... i had to buy a fuel pump relay from nissan for 85 bucks. and two weeks later come to find out after i call and ask where its at they dont even make it anymore....

SoloII///M

iTrader: (13)

BP went away a few years ago. It was replaced with XP.

Evil Aviator

I thought the OP meant Bridge Port and I assumed he was racing in E Mod, lol. It is possible that his local region still has the B Prepared class. I think the caliper mod is OK in either class, but I'm not going to spend an hour reading the rules to find out.