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Old 01-26-2006, 10:18 PM   #1
Legacy777
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Default Brake Math/Torque Spreadsheet

I may have posted this before, but I've had some time to go through the spreadsheet and clean things up, and make quite a bit of improvements. The biggest being a 'Brake Torque Calculator'. Let's say you want to swap some WRX brakes onto your 90 Legacy. Choose your car from the drop down menu, and the WRX as what you want to go to, and the calculator will spit out the percent change in brake torque and whether the shift is frontward or rearward.

If you don't see your vehicle in there and have information on your car, please let me know and I will add it. Likewise, if you see anything that looks incorrect or suspect, please let me know.

http://www.main.experiencetherave.co.../brakemath.xls

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Old 01-26-2006, 11:28 PM   #2
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awesome - thanks for all the hard work...
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Old 01-27-2006, 11:27 AM   #3
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Great job Josh. I have used your previous spreadsheet and it worked very well. Thanks for sharing all your hard work.

Ken
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Old 01-28-2006, 09:35 AM   #4
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Quote:
Originally Posted by Legacy777
I may have posted this before, but I've had some time to go through the spreadsheet and clean things up, and make quite a bit of improvements. The biggest being a 'Brake Torque Calculator'. Let's say you want to swap some WRX brakes onto your 90 Legacy. Choose your car from the drop down menu, and the WRX as what you want to go to, and the calculator will spit out the percent change in brake torque and whether the shift is frontward or rearward.

If you don't see your vehicle in there and have information on your car, please let me know and I will add it. Likewise, if you see anything that looks incorrect or suspect, please let me know.

http://www.main.experiencetherave.co.../brakemath.xls

Josh

The Subaru 4-pots are not an upgrade in braking power from WRX sliders according to this spreadsheet, how is that?
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Old 01-28-2006, 10:15 AM   #5
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Quote:
Originally Posted by richde
The Subaru 4-pots are not an upgrade in braking power from WRX sliders according to this spreadsheet, how is that?
http://forums.nasioc.com/forums/show...&highlight=h6s

http://forums.nasioc.com/forums/show...&highlight=h6s[/quote]
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Old 01-28-2006, 01:09 PM   #6
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[/quote]


Wow, thanks for turning on the clue light!
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Old 01-28-2006, 01:39 PM   #7
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Quote:
Originally Posted by richde
The Subaru 4-pots are not an upgrade in braking power from WRX sliders according to this spreadsheet, how is that?

I guess you know already from reading...

Piston size is down...you give up a little power over the 02-05 2-pots...but gain it back in rearward bias and significantly better braking feel.
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Old 01-28-2006, 07:31 PM   #8
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You're welcome guys. Please let me know if you see any errors in the caliper piston size or rotor data.

Also, if you have any other MY's that you know, please let me know, and I will add them.
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Old 02-14-2006, 12:08 AM   #9
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Josh, I like this version much more.

Here's SVX data if you want to add it: http://www.subaru-svx.net/forum/showthread.php?t=29007

rotor OD is 302mm front 290mm rear
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Old 02-14-2006, 08:53 AM   #10
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the STi only has 2 pot?

Brake Data >> Subaru Brake Caliper Piston Diameter Data >> 04 STi listed twice

??

...i think i may be reading it wrong

and the 1995 L AWD, does that have abs or not, and originally equipped with a rear drum?
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Old 02-14-2006, 06:30 PM   #11
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Quote:
Originally Posted by THAWA
Josh, I like this version much more.

Here's SVX data if you want to add it: http://www.subaru-svx.net/forum/showthread.php?t=29007

rotor OD is 302mm front 290mm rear
Thanks Hardy.

I'll add it to the brake info section. I don't think I'll add it to the part where I calculate brake torques since the SVX calipers are not swappable onto other subaru models. At least that's what I've understood. Correct me if I'm wrong.
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Old 02-14-2006, 06:43 PM   #12
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Quote:
Originally Posted by psyber_0ptix
the STi only has 2 pot?

Brake Data >> Subaru Brake Caliper Piston Diameter Data >> 04 STi listed twice

??

...i think i may be reading it wrong

and the 1995 L AWD, does that have abs or not, and originally equipped with a rear drum?
The STi Brembro's are definitely 4-pots. The reason it's listed the way it is, is because the pistons are not the same size. The trailing piston is smaller then the leading piston. The reason it's like this is because there is a self-energizing or wedging effect of the pad. By staggering the size of pistons, you include this effect into your calculations, and the resultant setup provides a more equal force distribution from front to rear of the brake pad.


There was a lot of different configurations for the 95 Impreza. The configuration I give is for 4-wheel discs. The calculation is much more complex for drum brakes, and since I don't have all the information needed, I don't include options for drum brakes. The only model that had 4-wheel discs was the 2.2 liter LX, and it had ABS standard.

I will add that clarification to the spreadsheet.

Josh
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Old 02-14-2006, 08:21 PM   #13
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Quote:
Originally Posted by THAWA
Josh, I like this version much more.

Here's SVX data if you want to add it: http://www.subaru-svx.net/forum/showthread.php?t=29007

rotor OD is 302mm front 290mm rear

I posted a question in that thread. Can you answer it?
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Old 02-14-2006, 09:03 PM   #14
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Quote:
Originally Posted by Legacy777
Thanks Hardy.

I'll add it to the brake info section. I don't think I'll add it to the part where I calculate brake torques since the SVX calipers are not swappable onto other subaru models. At least that's what I've understood. Correct me if I'm wrong.
I believe they're swapable. I know the rear calipers are as they are the same exact calipers used on all the other cars with the same size piston (90-94 Leg wagon, Turbo, RS, GT, etc). The bracket is similar to 00-04 legacy except it's designed for the old style of pads. The fronts I believe have the same mounting pattern, but I'll verify that next time I take off the wheels.
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Old 02-15-2006, 09:03 AM   #15
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Yeah it was the mounting pattern of the bracket is what I heard was different....but maybe not. Since the SVX has such large brakes, I would have figured if they were swappable, people would be using them....
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Old 02-15-2006, 09:37 PM   #16
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You'd have to find discs to match, remember 5x114.3mm.
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Old 02-18-2006, 09:20 PM   #17
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Ok....that's what was different.
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Old 02-18-2006, 09:27 PM   #18
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um i get a your port 8080 is borked...
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Old 02-21-2006, 05:22 PM   #19
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Try again,

If it still doesn't work, try this

https://www.mail.experiencetherave.c.../brakemath.xls
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Old 01-18-2007, 05:19 PM   #20
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Stoptech 4pots + 328mm rotor?

I thought we knew the piston diameter for those?
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Old 05-26-2008, 09:01 PM   #21
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No options for Foresters..
I don't know that data offhand.
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Old 05-27-2008, 01:59 AM   #22
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You know, I really want to thank you for writing the spreadsheet. I downloaded it a year or so ago and it's really useful. It's full of stuff that a lot of people can't wrap their heads around so it's a good thing it's getting a bump.
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Old 05-27-2008, 03:32 AM   #23
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The Forester uses Impreza stuff, so 02 and ealier uses Impreza sedan parts. The 03 steps up to the WRX front rotor and becomes increasingly front biased (dumb). That's all.

I can only assume the change to the WRX front rotors was to aid with heat dissipation and braking when towing, although, I hate messing up the bias more. They should have just thrown on the larger Outback rear rotors when they upped the front ones, it's a much better setup, helps more with heat, braking, and actually neutrals out the bias.

Awesome spreadsheet Legacy777!!!

I don't know if I'd worry too much about the Forester setup, but you can add it if you want. Older Impreza setup front and rear. In 03 with the redesign, the front went to the larger WRX rotor, still small Impreza rear, at least for the XT model. I have no clue about the NA models if they were also upped to the WRX front rotor. The brake booster and calipers are just the Impreza stuff, so nothing fancy there. I have no clue about the new 08 Forester though...
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Old 05-27-2008, 03:44 AM   #24
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well, we don't know if the prop valve changed, plus if the car has ebd it doesn't really matter as much.
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Old 08-18-2009, 11:33 AM   #25
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Is there any data for Impreza WRXs newer than 2005?
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