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5-lug...brake balance?


Numbchux
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just wondering how the brake balance is on those of you using EJ front brakes. anyone using upgraded front calipers? my buddy keeps telling me I should get 4-pot fronts, but but since I can't match it with the 2-pots in the rear, I'll probably end up with some nasty understeer under hard braking....

 

thoughts?

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Right now, I'm running just stock Impreza calipers (single pot) and XT6 calipers in the back of my RX. Stopping is wonderful, no understeer and will stop on a dime. However, since you're buddy is talking about 4 pots in the front, you can still use the stock single pot calipers in the back but I would highly recommend an aftermarket proportioning valve instead of the stock one, so then you can adjust how it stops, front to rear. If you DO want to upgrade the rear to a 2 pot caliper setup, this link might have some information for you since I am also thinking about going 4 pot front and 2 pot rear.

http://www.xt6.net/forum/viewtopic.php?t=6175&postdays=0&postorder=asc&start=0

 

Sexy!:brow:

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i have 2 pot 96 WRX calapers on the front and single pot Nissan SX200 calapers on the rear. stops awesome. no dipping or diving. may consider ceramic pads when the current ones need replaceing...

 

-=Suberdave=-

http://www.suberdave.com

 

nice, currently I'm running stock EA82 front calipers, and 200SX rears. maybe I'll just get 2-pot WRX fronts....that'd be a step up, and wouldn't mess with my balance too badly.

 

I've got all the parts for the swap using '92 legacy front stuff from the same donor car as my engine.

 

it'll be awhile before I can actually get the conversion in there, mostly since I can't bear to waste all these sets of good tires mounted on 13" wheels (specifically the snow tires :headbang: ). But I want to start collecting the parts now, including having the rear rotors turned, and cryo'ed.

 

and definately some nice pads

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I'm also in the middle of the 5 lug swap, just the XT-6 right now, but in secret plans i'll be using the Legacy Turbo front calipers and hubs. I think an aftermarket proportioning valve would be a great idea. Also, if you have the rear discs, which i'm assuming if you are doing the 5 lug then you do, you can use any newer subaru braided steel brakeline kit, just taylor it to your app, forester for the lifted rigs, and impreza for the stock bits.

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I'm also in the middle of the 5 lug swap, just the XT-6 right now, but in secret plans i'll be using the Legacy Turbo front calipers and hubs. I think an aftermarket proportioning valve would be a great idea. Also, if you have the rear discs, which i'm assuming if you are doing the 5 lug then you do, you can use any newer subaru braided steel brakeline kit, just taylor it to your app, forester for the lifted rigs, and impreza for the stock bits.

 

yep, I'll definately be running braided SS lines. and yes, already running rear discs, and will use the larger XT6 ones.

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Just want to comment on the brake balance thing since I went through a lot of stuff on my car.

 

The newer gen subies use a diagonal circuit brake system, and I would venture to say the older gen may use a similar setup to help maintain some amount of braking in the event of a failure. The problem with this is, fitting an aftermarket adj. proportioning valve is pretty much futal unless you replumb all the lines, and/or sacrafice the safety of the dual circuit design.

 

I will caution about upgrading only the front brakes without doing something in the rear. The car will dive severely under hard/panic braking. I had this very problem along with some others when I upgraded to WRX front brakes. I got in a panic situation, the fronts locked up much sooner then I was used to compared to the old brakes and I hit the guy in front of me.

 

There's so much you can learn about braking and tweaking this stuff, but from what I've found, the best balance is about a 10% shift rearward in brake torque compared to the original factory setup. This is mainly because the factory adds a little bit of front bias because your normal driver reacts better to plowing forward in a turn vs. the rear end coming around.

 

Here is a spreadsheet I have created with various newer gen brake caliper & rotor information. It can be used to calculate the changes in brake torque when swapping calipers & rotors. There is a brake torque calculator with drop down menus on one of the tabs. The formulas are pretty straight forward so you could create your own sheet if you have information on the older gen brakes.

 

The main things you need for the calculation are:

Outer disc diameter

Effective disc diameter

Caliper piston diameter

 

Here's the spreadsheet

http://www.main.experiencetherave.com:8080/subaru/techinfo/brakemath.xls

 

Josh

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