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BBK Brake Bias List


praedet

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Ok folks, I have been trying to check the biasing of the many brake systems that are out there.

 

I am going to try and keep an updated list. If you have a BBK system you want to check, or for that matter, if you want to understand what changing brake pads does, post the size of the rotor, the type of caliper (fixed/floating), how many pistons it has, and what diameter they are. If you are asking about simply a brake pad change, post the mu of the pad you will be using…

 

Now, to explain how I did this. I keep everything the same in the brake system up to the caliper. I assume that the coefficient of friction (brake pad mu) is the same from the stock system to the BBK unless otherwise specified. Taking out the inefficiencies and difference due to fixed and floating, and the stiffness of the caliper itself (this does make a difference, but it is small enough that we can simplify for these nonlinearities), the torque generated by the brake set-up is a function of piston size, # of pistons, and effective radius. With the stock front set-up you have 2 42.8 mm pistons that act like 4. With the BBK set-up you have 4 X mm pistons, or 2 X mm pistons and 2 Y mm pistons. I have pulled the effective radius for the Subaru set-ups from another site that got them from FSMs. The BBK effective radius is based on the STi Brembo set-up, with effective diameter = rotor diamter - largest piston size*5/4. With this, I calculated the difference between the torque generated by the stock set-up, and the torque generated by the BBK set-ups. I did not calculate the system’s ability to tolerate heat. This is looking at braking once with the system in a fixed temperature regime. I then calculate the rear set-up the same way. With no proportion valve interaction, the Front bias is Front Torque/(F Torque + Rear Torque) and the Rear bias is R Torque/(F Torque + R Torque). I can calculate this for both the stock system and the upgraded system. I can also compare the F+R torque of the upgraded system to the Stock system. This gives an idea of the pedal force vs. stock. Remember that the pedal force vs. stock does not take into account the “give” of a floating caliper vs. the stiffer fixed caliper.

 

Here is the resource I used to calculate this stuff.

 

Remember, all brake pads are equal in this. Simply upgrading the pad mu from 0.3 to 0.4 increases brake torque by 1/3. If you do a BBK front w/ a mu higher than 0.35, but leave the rear stock (0.35), your bias will drastically shift to the front...

 

Also, I added the Racing Brake rear kit which moves the stock caliper out and uses a 316x18 mm rotor. I have put a calculation in on all BBKs and the LGT/OXT stock set-ups with this kit since it is an easy/cheap upgrade...

 

Now, the list.

 

Front Brakes

           05 LGT     05 OBXT    iON4pt330   iON4pt310    RB4pt322    RB6pt355   Rot4pt330   Rot6pt330   Rot6pt355   STI4pt326
#pot         2           2           4           4           4           6           4           6           6           4
Caliper    float       float        fix         fix         fix         fix         fix         fix         fix         fix     float/fix
Pist 1      42.8        42.8        41.3        38.1        38.0        40.0        42.9        40.5        40.5        46.0    mm
Pist 2      42.8        42.8        38.1        38.1        38.0        38.0        38.2        34.9        34.9        40.0    mm
Pist 3      0.0         0.0         0.0         0.0         0.0         27.0        0.0         30.2        30.2        0.0     mm
Rotor       316         294         330         310         322         355         330         330         355         326     mm
Eff Rot     261         247         278         262         275         305         276         279         304         268     mm
mu          0.35        0.35        0.50        0.50        0.45        0.45        0.40        0.40        0.40        0.40

Rear Brakes

           05 LGT     05 OBXT    iON2pt310   Rot2pt290   Rot4pt330   STI2pt316   RB316Stoc
#pot         1           1           4           2           4           2           1
Caliper    float       float        fix         fix         fix         fix        float    float/fix
Pist 1      32.0        32.0        38.1        40.5        30.2        36.0        32.0    mm
Pist 2      0.0         0.0         0.0         0.0         30.2        0.0         0.0     mm
Rotor       290         266         310         290         330         316         316     mm
Eff Rot     254         230         262         239         292         268         280     mm
mu          0.35        0.35        0.50        0.40        0.40        0.40        0.35

Brake Bias

[b][color="Red"]05-07 LGT Brakes[/color][/b]                                [color="RoyalBlue"][i]Stock LGT Front            RB 316mm[/i][/color]
                     Front     Rear                                    Front     Rear
Tbrake                10349      2815lb*in        Tbrake                10349      3103lb*in
%                     78.6%     21.4%             %                     76.9%     23.1%
Ttotal brakes          2194lb*ft                  Ttotal brakes          2242lb*ft
F/R                    3.68                       %Stock Force           2.2%
                                                 F/R                    3.34

[color="red"][b]05 OUTBACK XT[/b][/color]
[color="red"][color="RoyalBlue"][i]05 OXT Stock                                      OXT Stock Front            RB 316mm[/i][/color][/color]
                     Front     Rear                                    Front     Rear
Tbrake                 9794      2549lb*in        Tbrake                10778      3103lb*in
%                     79.3%     20.7%             %                     77.6%     22.4%
Ttotal brakes          2057lb*ft                  Ttotal brakes          2313lb*ft
%Stock Force          -6.2%                       %Stock Force           5.5%
F/R                    3.84                       F/R                    3.47

[color="Red"][b]iON[/b][/color]
[color="royalblue"][i]APR 310mm 4-pot            Stock Rear             APR 330mm 4-pot            Stock Rear[/i][/color]
                     Front     Rear                                    Front     Rear
Tbrake                 8244      2815lb*in        Tbrake                 9512      2815lb*in
%                     74.5%     25.5%             %                     77.2%     22.8%
Ttotal brakes          1843lb*ft                  Ttotal brakes          2055lb*ft
%Stock Force         -16.0%                       %Stock Force          -6.4%
F/R                    2.93                       F/R                    3.38

[color="royalblue"][i]APR 310mm 4-pot            RB 316mm               APR 330mm 4-pot            RB 316mm[/i][/color]
                     Front     Rear                                    Front     Rear
Tbrake                 8244      3103lb*in        Tbrake                 9512      3103lb*in
%                     72.7%     27.3%             %                     75.4%     24.6%
Ttotal brakes          1891lb*ft                  Ttotal brakes          2103lb*ft
%Stock Force         -13.8%                       %Stock Force          -4.2%
F/R                    2.66                       F/R                    3.07

[color="royalblue"][i]APR 310mm 4-pot            2-pot Rear             APR 330mm 4-pot            2-pot Rear[/i][/color]
                     Front     Rear                                    Front     Rear
Tbrake                 8244      4122lb*in        Tbrake                 9512      4122lb*in
%                     66.7%     33.3%             %                     69.8%     30.2%
Ttotal brakes          2061lb*ft                  Ttotal brakes          2272lb*ft
%Stock Force          -6.1%                       %Stock Force           3.6%
F/R                    2.00                       F/R                    2.31


[color="Red"][b]RACING BRAKE[/b][/color]
[color="royalblue"][i]RB 316mm 4-pot             Stock Rear             RB 322mm 4-pot             Stock Rear[/i][/color]
                     Front     Rear                                    Front     Rear
Tbrake                 8392      2815lb*in        Tbrake                 8580      2815lb*in
%                     74.9%     25.1%             %                     75.3%     24.7%
Ttotal brakes          1868lb*ft                  Ttotal brakes          1899lb*ft
%Stock Force         -14.9%                       %Stock Force         -13.4%
F/R                    2.98                       F/R                    3.05

[color="royalblue"][i]RB 355mm 6-pot             Stock Rear             RB 316mm 4-pot             RB 316mm[/i][/color]
                     Front     Rear                                    Front     Rear
Tbrake                12454      2815lb*in        Tbrake                 8392      3103lb*in
%                     81.6%     18.4%             %                     73.0%     27.0%
Ttotal brakes          2545lb*ft                  Ttotal brakes          1916lb*ft
%Stock Force          16.0%                       %Stock Force         -12.7%
F/R                    4.42                       F/R                    2.70

[color="royalblue"][i]RB 322mm 4-pot             RB 316mm               RB 355mm 6-pot             RB 316mm[/i][/color]
                     Front     Rear                                    Front     Rear
Tbrake                 8580      3103lb*in        Tbrake                12454      3103lb*in
%                     73.4%     26.6%             %                     80.1%     19.9%
Ttotal brakes          1947lb*ft                  Ttotal brakes          2593lb*ft
%Stock Force         -11.3%                       %Stock Force          18.2%
F/R                    2.76                       F/R                    4.01

[color="Red"][b]ROTORA[/b][/color]
[i][color="RoyalBlue"]Rotora 330mm 4-po          Stock Rear             Rotora 330mm 6-po          Stock Rear[/color][/i]
                     Front     Rear                                    Front     Rear
Tbrake                 9854      2815lb*in        Tbrake                11402      2815lb*in
%                     77.8%     22.2%             %                     80.2%     19.8%
Ttotal brakes          2112lb*ft                  Ttotal brakes          2369lb*ft
%Stock Force          -3.8%                       %Stock Force           8.0%
F/R                    3.50                       F/R                    4.05

[color="RoyalBlue"][i]Rotora 355mm 6-po          Stock Rear             Rotora 330mm 4-po          RB 316mm[/i][/color]
                     Front     Rear                                    Front     Rear
Tbrake                12422      2815lb*in        Tbrake                 9854      3103lb*in
%                     81.5%     18.5%             %                     76.1%     23.9%
Ttotal brakes          2539lb*ft                  Ttotal brakes          2160lb*ft
%Stock Force          15.7%                       %Stock Force          -1.6%
F/R                    4.41                       F/R                    3.18

[i][color="RoyalBlue"]Rotora 330mm 6-po          RB 316mm               Rotora 355mm 6-po          RB 316mm[/color][/i]
                     Front     Rear                                    Front     Rear
Tbrake                11402      3103lb*in        Tbrake                12422      3103lb*in
%                     78.6%     21.4%             %                     80.0%     20.0%
Ttotal brakes          2417lb*ft                  Ttotal brakes          2587lb*ft
%Stock Force          10.2%                       %Stock Force          17.9%
F/R                    3.67                       F/R                    4.00

[i][color="RoyalBlue"]Rotora 330mm 4-po          2-pot Rear             Rotora 330mm 6-po          2-pot Rear[/color][/i]
                     Front     Rear                                    Front     Rear
Tbrake                 9854      4240lb*in        Tbrake                11402      4240lb*in
%                     69.9%     30.1%             %                     72.9%     27.1%
Ttotal brakes          2349lb*ft                  Ttotal brakes          2607lb*ft
%Stock Force           7.1%                       %Stock Force          18.8%
F/R                    2.32                       F/R                    2.69

[i][color="RoyalBlue"]Rotora 355mm 6-po          2-pot Rear             Rotora 330mm 4-po          4-pot Rear[/color][/i]
                     Front     Rear                                    Front     Rear
Tbrake                12422      4240lb*in        Tbrake                 9854      5780lb*in
%                     74.6%     25.4%             %                     63.0%     37.0%
Ttotal brakes          2777lb*ft                  Ttotal brakes          2606lb*ft
%Stock Force          26.6%                       %Stock Force          18.8%
F/R                    2.93                       F/R                    1.70

[color="RoyalBlue"][i]Rotora 330mm 6-po          4-pot Rear             Rotora 355mm 6-po          4-pot Rear[/i][/color]
                     Front     Rear                                    Front     Rear
Tbrake                11402      5780lb*in        Tbrake                12422      5780lb*in
%                     66.4%     33.6%             %                     68.2%     31.8%
Ttotal brakes          2864lb*ft                  Ttotal brakes          3034lb*ft
%Stock Force          30.5%                       %Stock Force          38.3%
F/R                    1.97                       F/R                    2.15

[color="Red"][b]STI BREMBO[/b][/color]
[color="RoyalBlue"][i]STI 326mm 4-pot            Stock Rear             STI 326mm 4-pot            2-pot Rear[/i][/color]
                     Front     Rear                                    Front     Rear
Tbrake                10778      2815lb*in        Tbrake                10778      3759lb*in
%                     79.3%     20.7%             %                     74.1%     25.9%
Ttotal brakes          2265lb*ft                  Ttotal brakes          2423lb*ft
%Stock Force           3.3%                       %Stock Force          10.4%
F/R                    3.83                       F/R                    2.87

[color="royalblue"][i]STI 326mm 4-pot            RB 316mm[/i][/color]
                     Front     Rear
Tbrake                10778      3103lb*in
%                     77.6%     22.4%
Ttotal brakes          2313lb*ft
%Stock Force           5.5%
F/R                    3.47

[b][color="Red"]STOPTECH[/color][/b]
[i][color="RoyalBlue"]ST 332mm 4-pot             Stock Rear             ST 332mm 4-pot             RB 316mm[/color][/i]
                     Front     Rear                                    Front     Rear
Tbrake                10133      2815lb*in        Tbrake                10133      3103lb*in
%                     78.3%     21.7%             %                     76.6%     23.4%
Ttotal brakes          2158lb*ft                  Ttotal brakes          2206lb*ft
%Stock Force          -1.6%                       %Stock Force           0.5%
F/R                    3.60                       F/R                    3.27

[color="royalblue"][i]ST 328mm 4-pot             Stock Rear             ST 328mm 4-pot             RB 316mm[/i][/color]
                     Front     Rear                                    Front     Rear
Tbrake                 7106      2815lb*in        Tbrake                 7106      3103lb*in
%                     71.6%     28.4%             %                     69.6%     30.4%
Ttotal brakes          1653lb*ft                  Ttotal brakes          1701lb*ft
%Stock Force         -24.6%                       %Stock Force         -22.4%
F/R                    2.52                       F/R                    2.29

 

Brake Pads

Man.        Type       Type       min T   max T   min mu  max mu   Rating
Endless   Vita Nuv non-asbesots     32     570     0.30    0.35    Street
Endless     SS-Y      ceramic       32     716     0.38    0.48  A. Street
Endless     SS-S      ceramic       32     932     0.35    0.43    Auto-X
Endless     SS-M      ceramic       32     986     0.30    0.40   L. Track
Endless     CC-X   semi-metalic    120     1300    0.38    0.50    Track
Endless     CC-R   semi-metalic    300     1500    0.35    0.42   H. Track
Carbotech  Bobcat     ceramic       40     900     0.45    0.45    Auto-X
Carbotech   XP9         ???        ???     1400    ???     ???    L. Track
Carbotech   XP10        ???        ???     1600    0.60    0.60    Track
Carbotech   XP11        ???        ???     ???     0.65    0.65   H. Track
Ferrodo   DS 2500       ???        ???     ???     0.50    0.50     ???

Pad Levels from Low to High: Stock, Street, Agressive (A) Street, Auto-X, Light (L) Track, Track, Heavy (H) Track

Edited by praedet
:spin:
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I pm'ed Street Image to try and get the info I need for that. I will post it when I get it Allen.

 

Interestingly, if you were to use SS-Ms in the front (mu = ~0.4) and Bobcats in the rear (mu = ~0.5) you would get 68.7%/31.3% F/R bias...

:spin:
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Dan,

The mu values for the Endless and Carbotech offereings are on their sites, and has been posted here. I don't know for those two though. I would do a search on nasioc, or e-mail the vendors.

Ted

 

Does this deserve a sticky? :D

:spin:
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Ted - where can you get teh mu data? I checked Hawk and Cobb for mine and got nada.

 

Hawk tends to be very stingy with their technical data, don't know about Cobb. I have Ferodo's(ds2500), and they do give out their specs: 0.5 mu across their MOT up to 1000.

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Hey, do the Rotora 4-pot! :D

 

I emailed my contact at Rotora.

 

Here's a copy of it

 

xxxxx, got another question for you.

 

Is it possible that you could get me the following:

 

Front 330mm 1-piece kit

# of Pistons = 4

Type of Caliper =

Piston Size =

Rotor Diameter = 330 mm

 

Rear 2-piston 1-piece

# of Pistons = 2

Type of Caliper =

Piston Size =

Rotor Diameter =

 

If you could also give me the information regarding the 2-piece kits it would be appreciated.

 

Front 2-piece kit

# of Pistons = 4

Type of Caliper =

Piston Size =

Rotor Diameter = 330 mm

 

Rear 4-piston 2-piece

# of Pistons = 4

Type of Caliper =

Piston Size =

Rotor Diameter =

 

Thanks for taking the time to help out.

"some say, his arms are made of coiled adamantium fibers. And that he tops his cereal with nuts and bolts. All we know is, he's called the Jose."
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Excellent, I ask him for the:

4-pot front piston sizes, I know the rotor is 330 mm

6-pot front piston sizes and rotor diameter

4-pot rear piston sizes and rotor diameter

4-pot rear piston sizes and rotor diameter

Thanks,

Ted

:spin:
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Worst case, I can make a sacrifise and pull mine to measure. Do you want me to measure the O.D. of the pistons? (I have a set of measuring calipers in my toolbox.)
"some say, his arms are made of coiled adamantium fibers. And that he tops his cereal with nuts and bolts. All we know is, he's called the Jose."
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Yep! Hopefully you won't have to do that. Did you upgrade your rear pads when you did the front brakes?

 

Ted

 

 

No, Rotora's setup comes with street pads. You can opt to change to more aggressive pads, which I am getting ready to do. My rear setup is still just like OEM.

 

That being said, I posted on the Rotora thread regarding the pad size in case anyone wants to run different types of pads.

 

I'm thinking about biting the bullet for the rear set.

 

I think I will wait for captain to tell us the sizes so that we can calculate the bias before I bite the bullet. I got a GREAT offer.

 

Armed with that, I can then make a better decision on which pads I want to use. Maybe I will run something like Hawk HPS up front and HP+ in the rear.

"some say, his arms are made of coiled adamantium fibers. And that he tops his cereal with nuts and bolts. All we know is, he's called the Jose."
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Wait' date=' so the BBK's provide less torque? How are they better, then?[/quote']

 

 

Improved brake bias and improved heat management. Improved brake bias will improve braking distances as it will make the rear wheels not be underutilized when heavy braking is taking place.

 

In addition, the larger rotor will improve heat management which will give you more consistent braking under heavy loads (i.e. track events, etc.)

"some say, his arms are made of coiled adamantium fibers. And that he tops his cereal with nuts and bolts. All we know is, he's called the Jose."
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A little diggin on Nasioc.com turns up that for the XT front (WRX), the rotors are 294mm diameter and the piston size is 42.8mm. The rear should probably be very similar but with a different pad, to the WRX so I'm going to go with 266mm rotor and 38.1mm piston.

 

I'll have to wait until the weekend when I have time to pull the rears off the XT and give a good measure, though I'm sure that they'll be the very similar to the wrx to maintain bias.

 

Also, this might help a bit too.

 

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

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That link is awesome because it gives the actual effective radius from the FSM. The problem is that we don't have that for the BBKs. I am going to assume that the effective diameter for BBKs is the rotor diameter - largest piston diameter*5/4

 

That is what the front and rear of the STi Brembos are. With that in place I have redone the numbers, and included the XT brakes based on 02-05 WRX brakes...

 

Ted

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Improved brake bias and improved heat management. Improved brake bias will improve braking distances as it will make the rear wheels not be underutilized when heavy braking is taking place.

 

In addition, the larger rotor will improve heat management which will give you more consistent braking under heavy loads (i.e. track events, etc.)

 

I can replace my front pads with bars of soap. That will create less heat and shift braking bias to the rear.

:lol:

 

So i guess BBK's allow you to run grippier pads and still deal with the heat they create?

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I can replace my front pads with bars of soap. That will create less heat and shift braking bias to the rear.

:lol:

 

So i guess BBK's allow you to run grippier pads and still deal with the heat they create?

 

 

Si. I suppose you can see it that way. Basically most of the difference with BBKs involve brake feel/modulation/heat management/consistency.

 

I wouldn't necesarily expect a lower braking distance when using a BBK. I would look out for consistency under harsh conditions, and good brake modulation.

 

I feel that anyone who plans to keep using their LGT for the street and auto-x only doesn't really have to look into a BBK.

"some say, his arms are made of coiled adamantium fibers. And that he tops his cereal with nuts and bolts. All we know is, he's called the Jose."
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The iON AP Racing kit is the best combination of heat management/perfect biasing I have seen so far. They did their homework. 70/30 is ideal in my mind. Obviously, that is as long as you put DS2500s on the rear too...

 

RB is starting to go towards the unsafe side of things, and either STi swap has a worse bias vs. stock. If you add in the brake dive present in the stock LGT, a too rear biased system will lock up the rears very quickly...

 

Ted

:spin:
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