praedet Posted March 15, 2006 Share Posted March 15, 2006 (edited) 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 June 26, 2008 by praedet Link to comment Share on other sites More sharing options...
TSiWRX Posted March 15, 2006 Share Posted March 15, 2006 Hey, do the Rotora 4-pot! <-- I love Winky, my "periwinkle" (ABP) LGT! - Allen / Usual Suspect "DumboRAT" / One of the Three Stooges '16 Outback, '16 WRX, 7th Subaru Family Link to comment Share on other sites More sharing options...
sutter2k Posted March 15, 2006 Share Posted March 15, 2006 Is it safe to assume mods setup are going to include pads with a greater friction that stock? Though I think its better you kept this out of the calculations up top. Link to comment Share on other sites More sharing options...
praedet Posted March 15, 2006 Author Share Posted March 15, 2006 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... Link to comment Share on other sites More sharing options...
praedet Posted March 15, 2006 Author Share Posted March 15, 2006 Yeah, but most people are wondering whether or not to just do pads, lines, and fluid, or step up to a BBK. For biasing, I thought keeping the pads the same would be best. Ted Link to comment Share on other sites More sharing options...
PGT Posted March 15, 2006 Share Posted March 15, 2006 Ted - where can you get teh mu data? I checked Hawk and Cobb for mine and got nada. Link to comment Share on other sites More sharing options...
praedet Posted March 15, 2006 Author Share Posted March 15, 2006 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? Link to comment Share on other sites More sharing options...
captainmorgan Posted March 15, 2006 Share Posted March 15, 2006 Some info from an OBXT would be helpful to some as well! Its probably pretty easy to dig up the fronts (wrx), but the info on the rears is pretty limited Link to comment Share on other sites More sharing options...
edmundu Posted March 15, 2006 Share Posted March 15, 2006 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. Link to comment Share on other sites More sharing options...
praedet Posted March 15, 2006 Author Share Posted March 15, 2006 Get me the XT stuff and I will run the numbers... Link to comment Share on other sites More sharing options...
sutter2k Posted March 15, 2006 Share Posted March 15, 2006 btw: axiss ultimates appear to be 0.46 Ferodo's(ds3000) are 62mu!! Link to comment Share on other sites More sharing options...
jsalicru Posted March 15, 2006 Share Posted March 15, 2006 Hey, do the Rotora 4-pot! 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." Link to comment Share on other sites More sharing options...
praedet Posted March 15, 2006 Author Share Posted March 15, 2006 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 Link to comment Share on other sites More sharing options...
jsalicru Posted March 15, 2006 Share Posted March 15, 2006 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." Link to comment Share on other sites More sharing options...
praedet Posted March 15, 2006 Author Share Posted March 15, 2006 Yep! Hopefully you won't have to do that. Did you upgrade your rear pads when you did the front brakes? Ted Link to comment Share on other sites More sharing options...
captainmorgan Posted March 15, 2006 Share Posted March 15, 2006 I just got my Rotora 4pot/2pot setup last night. I can measure the calipers tonight if you like. Link to comment Share on other sites More sharing options...
praedet Posted March 15, 2006 Author Share Posted March 15, 2006 That would be great. Measure the XT stock set-up also! Main things I need, rotor diameters and piston diameters... Ted Link to comment Share on other sites More sharing options...
jsalicru Posted March 15, 2006 Share Posted March 15, 2006 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." Link to comment Share on other sites More sharing options...
05Limited Posted March 15, 2006 Share Posted March 15, 2006 Wait, so the BBK's provide less torque? How are they better, then? Link to comment Share on other sites More sharing options...
jsalicru Posted March 15, 2006 Share Posted March 15, 2006 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." Link to comment Share on other sites More sharing options...
captainmorgan Posted March 15, 2006 Share Posted March 15, 2006 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 Link to comment Share on other sites More sharing options...
praedet Posted March 15, 2006 Author Share Posted March 15, 2006 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 Link to comment Share on other sites More sharing options...
sutter2k Posted March 15, 2006 Share Posted March 15, 2006 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. So i guess BBK's allow you to run grippier pads and still deal with the heat they create? Link to comment Share on other sites More sharing options...
jsalicru Posted March 15, 2006 Share Posted March 15, 2006 I can replace my front pads with bars of soap. That will create less heat and shift braking bias to the rear. 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." Link to comment Share on other sites More sharing options...
praedet Posted March 15, 2006 Author Share Posted March 15, 2006 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 Link to comment Share on other sites More sharing options...
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