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Old 02-15-2008, 11:49 AM   #101
Jard
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Quote:
Originally Posted by AcquaCow View Post
I'm not sure he would...

If I can run H6's with 4-pots up front, which already transfer brake bias to the rear due to less front brake torque...

Running the H6 rears with RS front calipers shouldn't really upset it that much at all.

Ideally ctimpreza should get wrx rotors for the front as well.

-- Dave
You can run them...the question is "should you?"

I know I noticed a big brake bias change when I added the H6.
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Old 02-15-2008, 12:15 PM   #102
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Find subysouth's spreadsheet and calculate it out?
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Old 02-15-2008, 12:45 PM   #103
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Quote:
Originally Posted by ButtDyno View Post
Find subysouth's spreadsheet and calculate it out?
This one: http://www.main.experiencetherave.co.../brakemath.xls ?

-- Dave
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Old 02-15-2008, 12:51 PM   #104
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That's the only one I know of...
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Old 02-15-2008, 12:58 PM   #105
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According to that then,

He'd be keeping the stock 276x24mm front rotors and upgrading the rears from 266mm to 290mm...

According to the spreadsheet, that's only a 10% shift to the rear if he uses stock pads front and rear and is on stock pads now.

I'll re-run those #'s, as that sheet doesn't have specific info for the GC... I had to find a matching legacy entry...but I haven't had time to look at piston diameters in the calipers...

Using the same substitution, the sheet quotes 13% increased rear bias for 4-pot/H6 over stock RS setup, but only 2% if you do WRX front brakes with H6 rear.

-- Dave
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Old 02-15-2008, 02:39 PM   #106
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Quote:
Originally Posted by AcquaCow View Post
According to that then,

He'd be keeping the stock 276x24mm front rotors and upgrading the rears from 266mm to 290mm...

According to the spreadsheet, that's only a 10% shift to the rear if he uses stock pads front and rear and is on stock pads now.

I'll re-run those #'s, as that sheet doesn't have specific info for the GC... I had to find a matching legacy entry...but I haven't had time to look at piston diameters in the calipers...

Using the same substitution, the sheet quotes 13% increased rear bias for 4-pot/H6 over stock RS setup, but only 2% if you do WRX front brakes with H6 rear.

-- Dave
What's the comparative # for an '02 WRX adding the H6 rear?

Just so I can compare...
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Old 02-15-2008, 03:59 PM   #107
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Quote:
Originally Posted by Jard View Post
What's the comparative # for an '02 WRX adding the H6 rear?

Just so I can compare...
10.38% rearward.

Assuming you are using the same pad compound before/after.

12.64% rearward if you were on stock pads prior to the conversion and street pads after.

-- Dave
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Old 02-15-2008, 04:06 PM   #108
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Quote:
Originally Posted by AcquaCow View Post
10.38% rearward.

Assuming you are using the same pad compound before/after.

12.64% rearward if you were on stock pads prior to the conversion and street pads after.

-- Dave
I went to Bobcats at the same time I did it. That's cool info...thanks for crunching the numbers.

Now I know what a 12.64% rearward bias shift feels like.
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Old 02-15-2008, 04:14 PM   #109
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I'm gonna double-check that spreadsheet this weekend...

I want to figure out which legacy entries = GC, as I figure piston size will play into this...but not my too much...

-- Dave
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Old 02-15-2008, 09:30 PM   #110
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Alright, it looks like all of the caliper piston diameters are the same size for the Legacy/WRX/RS for the years I'm concerned with, so the #'s I posted earlier are right.

The spreadsheet has a calculator tab where you just pick before/after scenarios and it tells you the % difference...there's no manual calculation involved thankfully.

-- Dave
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Old 02-16-2008, 02:39 AM   #111
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I have a brighton with the rear drums . This probally throws the calculations way off of front rear bias %. H-6 brakes seem like a cost effective way to increase braking power, while also coverting to disc. Lots of great information.
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Old 03-18-2008, 11:21 AM   #112
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I recently nabbed a good deal on a set of 06 WRX 2-pot rears and decided to plug them into the brakemath.xls sheet.

The "H6" and rear 2-pots have identical brake torque according to the sheet, so my bias will not change... =)
I will remain at my previous 22% rearward shift.
[Edit]This is possibly not true, please see my post below[/Edit]


Here's some more info from that spreadsheet regarding upgrades from WRX brakes to various 4/2-pot combos...

Assuming stock WRX brakes as a starting point...
Subaru 4-pots added to the front, stock rear: 7.9% rearward, 9.6% rearward if upgraded to street pads all around.
Brembo's added to front, stock rear: 10% forward, 12.3% forward if upgraded to street pads all around.

Subaru 4-pots front, subaru 2-pot rear: 18.2% rearward, 22% rearward if upgraded to street pads all around.
Subaru 4-pots front, brembo 2-pot rear: 11.83% rearward, 14% rearward if upgraded to street pads all around.

Brembo 4-pot front, subaru 2-pot rear: .2% rearward, .33% if upgraded to street pads all around.
Brembo 4-pot front, brembo 4-pot rear: 6.9% forward, 7.5% forward if upgraded to street pads all around.

Just some #s to think about.

-- Dave

Last edited by AcquaCow; 04-17-2008 at 12:33 PM.
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Old 04-17-2008, 12:32 PM   #113
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Wow, so upon doing some more research I have discovered that brake torque % F/R is not the same as brake bias F/R.

We can pretty much disregard anything referencing that in this thread

More info here:
http://forums.nasioc.com/forums/show....php?t=1416144

-- Dave
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Old 04-17-2008, 01:08 PM   #114
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I just wanted to quote this post, as I think it is the most important in the brake torque vs bias question.

Quote:
Originally Posted by Legacy777 View Post
Mike,

I've looked at my sheet, and inputted some data in TCE's calculater. However there are some differences in the inputted data....

For kicks, I put in data on TCE's calculator for the STi brembros to try and match my sheet. I used .39 for pad Cf, both front & rear. The main difference I can see is that there may be some difference in how the effective disc diameter is calculated, but it shouldn't change things too much. I do not know the calculation TCE is using to calculate the effective disc diameter, and how it compares to the effective disc diameter given in the factory manuals.

What I did was subtract the effective disc diameter from the outer disc diameter. That is what I used for the pad height. For the brembro front's I got 2.28" & rear I got 1.89". When I put all that info in I got a Percentage of front bias of .742

I did the slider WRX config using 1.85" for the front pad height & 1.41" for the rear pad height.....I came up with a Percentage of front bias of .744

For the 4 & 2 pots I used 1.53" for the front pad height & 1.42" for the rear pad height. I came up with a Percentage of front bias of .694

So....pretty close to your numbers. I used all the data from my spreadsheet....I think you had a slightly different piston diameter then I did for one caliper....I don't remember which now.


Anyway....the bottom line and where I think your seeing the difference coming from is due to the fact I am using a percentage of brake torque change, while the numbers you're getting off of TCE's calculator are actual calculations of bias. It's been a while since I made all the changes to the spreadsheet, but I do recall talking with TCE about this very issue, bias vs. brake torque. A 25% change in brake torque may seem like a lot, but it may only yield a 0.05 percent change in bias when looking solely at the numbers. Actually vehicle response will vary depending on a lot of other variables, including weight shift, suspension, etc.


So that's my stab at what you're seeing, and why you're seeing the differences between the two calculators. I'm open to any and all comments as it's been a while since I've looked at this stuff.

Josh
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Old 06-17-2008, 12:54 PM   #115
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can a similar upgrade be done to the front with the front brackets and front h6 rotors?
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Old 06-17-2008, 01:00 PM   #116
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aren't fronts H6 the same size stock WRX?
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Old 06-18-2008, 04:04 AM   #117
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could be. maybe i'm thinking of the legacy gt calipers that are an inch bigger. i think those are thicker than the wrx rotors though.
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Old 06-18-2008, 04:08 AM   #118
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rotors i mean, rotors are an inch bigger.
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Old 08-04-2008, 02:49 PM   #119
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So after reading everything I'm pretty well confused. Is the rear braking bias something to be concerned with or not? I will be doing the H6 upgrade with Hawk HPS pads, new fluid and SS Lines.
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Old 08-04-2008, 09:10 PM   #120
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Quote:
Originally Posted by BoostUnderPressure03 View Post
So after reading everything I'm pretty well confused. Is the rear braking bias something to be concerned with or not? I will be doing the H6 upgrade with Hawk HPS pads, new fluid and SS Lines.
Do you have the Subaru 4pots up front or stock 2003 brakes?

if you have the stock 2003 brakes up front, there is nothing to be concerned about with the H6 rears. I had that setup for a few years; drove on the street, autoX & track with no issues.

G
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Old 09-17-2008, 10:36 PM   #121
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Quote:
Originally Posted by Gonz View Post
Do you have the Subaru 4pots up front or stock 2003 brakes?

if you have the stock 2003 brakes up front, there is nothing to be concerned about with the H6 rears. I had that setup for a few years; drove on the street, autoX & track with no issues.

G
So what if one was going from full stock to subaru 4-pot fronts and was wanting to do H6 rears? would it be recommended or discouraged based on regular driving with occasional track time?
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Old 01-15-2009, 12:54 PM   #122
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i'm about to do the H6 upgrade on an '02 wrx and i'm seeing on subarugenuineparts that there are 2 options

bracket + clip for $125

or

bracket only for $115

what clip are they talking about and is it necessary or something you can reuse off the stock wrx brakes?

a friend who has done the upgrade said he didnt use a clip but i want to double check before purchasing.
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Old 01-15-2009, 02:31 PM   #123
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nice write up good for people who want better brakes
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Old 01-15-2009, 03:13 PM   #124
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I usually sell the brackets only.
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Old 01-15-2009, 03:23 PM   #125
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you should be able to reuse the clips that are currently on your brackets.
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