Why do you need a BBK?

[Grinder34]

I've been mulling this over in my head and want to get some facts and insights from you guys.

Let's give you some background. For a track day I was running DTC-30s (which are a mild track pad) and some Hankook V12 tires (max summer, not extreme summer), and using ATE fluid. At the track day i totally overpowered my OEM brake setup. I ate a whole set of pads, boiled my fluid (ok it was a bit old), and turned my gold rotors brownish and the red lettering is totally black now.

So now I'm thinking about upgrading. I understand any GOOD BBK will come with really nice rotors, usually 2-piece. The design is directional, and the rotors are bigger...all to help with cooling. So why wouldnt I get the same benefit of a BBK by putting equally well-designed 2-piece rotors on the Brembo caliper? What about the caliper itself makes the difference (assuming an equal number of pistons...like staying 4-pot). Clearly it must make a difference, with many/most/all? TA cars and race STIs using aftermarket brake setups. Is it just about the cheaper cost of replacements of mass-produced kits vs the pricey OEM pads and rotors?

I know that brake bias can play a part (for instance, my rear calipers look new, the pads look new, etc...), but I've seen some very fast cars using OEM rears with aftermarket front calipers. I believe the Element Tuning STI had this setup.

Thanks for the info guys!

ps. brake ducts are already in my future, just trying to figure out/justify a BBK.

 

[Spamby]

Calipers in a BBK may be larger than your factory Brembos. Larger in that the pistons may be larger. This would create a higher clamping area, especially utilizing larger pads, across the rotor. The larger mass may also help in keeping the calipers cool and preventing distortion/warping under high temps.
The larger rotor helping create more surface area to bite. The larger rotor to help control heat and to help prevent distortion/warping.
The two peice rotor to help control thermal growth of the rotor. The bolts on the hat allow the rotor to slip or grow.
Fresh fluid prior to a run will help combat brake fluid boil and brake performance. Given time in the system, the brake fluid will degrade and take on moisture. As you may know, moisture lowers the fluids boiling point.

Be careful with too large of a front brake as this may cause a very unbalanced braking system. Your fronts will lock way before the rears even have a chance to begin to clamp.

Running high speeds on a track and really working the brakes will cause a lot of the issues you have had, especially with the factory setup.

I would suspect the factory Brembo setup to be more biased to street and spirited driving scenarios, not that of a true race setup. They would be ok for a casual track driver but may not be the best for all out race... or maybe even moderate race duty.

I don't know if this answers or even helps but these are my thoughts. They do make sense in my head. I hope I'm not spewing bs?

 

[Ghostwhite]

More surface area, more area to heat up and better heat dissipation. Also have greater lever arm the further away from center you go, giving you more braking power. Brake ducts will absolutely help, I plan on going with a 2 piece rotor for cheaper replacements, if you only have to replace the rotor face you should save some money right?


Edit: I also agree with having a balanced system.

 

[Grinder34]

i agree, but everything seems to focus on the rotor. is it just that you can fit a bigger rotor with an aftermarket caliper?

 

[Spamby]

i agree, but everything seems to focus on the rotor. is it just that you can fit a bigger rotor with an aftermarket caliper?

yes, but i would still say that the piston diameters is going to be larger with the larger caliper and thus the larger rotor.

***Edit***

And the larger rotor gives you more surface area to bite on thus increasing braking performance and helping to control heat. Larger surface is more heat resitant.

 

[Grinder34]

There was never a problem with torque on the brake disc. The problem was with heat.

 

[Spamby]

And some brake ducts and cross drilled and slotted rotors will help reduce heat. Slots keep the brake dust off the rotor, and cross drilling helps cooling. a lot

Yes, it helps cooling but more importantly, be design, it helps vent gassing off of the rotor. Utilizing a smaller rotor, surface area, the drilling and slotting helps keep the smaller area from overheating. A larger flat area theoretically should sustain a cooler disk area whereas a smaller rotor, with no drilling/slotting would overheat before that of a larger disk.

which you have said some of that

 

[IGOTASTi]

Now I've heard drilled rotors cause more heat then non drilled rotors. Ahhhhhhh.

 

[Grinder34]

I guess I should focus my question:

What advantage do aftermarket CALIPERS offer over the OEM Brembo calipers?

Is the sole advantage the ability to fit larger rotors?

 

[Spamby]

We don't even have small brakes! My Subaru has bigger brakes than my buddies Dodge ram 2500!

Yes. We have large brakes for our cars and compared to a lot of others but not as big as a lot of others. I'll take some pics of my CTT's brakes this weekend when I change the pads. You'll be tryin to figure how to squirrel those monsters under your car... I know I have! lol

 

[Spamby]

Now I've heard drilled rotors cause more heat then non drilled rotors. Ahhhhhhh.

I have heard the same. I have heard a lot of debates regarding the drilled slotted rotors. yet, I haven't seen any concrete evidence regarding what is better. Mostly my brand/design is better than yours kinda stuff... so I keep an open mind.

I guess I should focus my question:

What advantage do aftermarket CALIPERS offer over the OEM Brembo calipers?

Is the sole advantage the ability to fit larger rotors?

Larger pistons and thus better clamping force.

Yes and yes. Larger pistons need larger rotors for larger contact surface.


Otherwise, going with a BBK of the same sized calipers and rotors might NOT be forward progress.

 

[Spamby]

Lol please do take pictures! Porsche likes to jam huge brakes into their cars lol. I cant wait to see this! Lol i love the look of huge calipers

http://www.igotasti.com/vBforum/showthread.php?4468-Spamby-s-08-STi

post #10

teaser.

Sorry Grinder, not meaning to crap on your thread!

 

[Ghostwhite]

I have heard the same. I have heard a lot of debates regarding the drilled slotted rotors. yet, I haven't seen any concrete evidence regarding what is better. Mostly my brand/design is better than yours kinda stuff... so I keep an open mind.







Larger pistons and thus better clamping force.

Yes and yes. Larger pistons need larger rotors for larger contact surface.


Otherwise, going with a BBK of the same sized calipers and rotors might NOT be forward progress.

Clamping force is the big thing, he hit the nail on the head. Larger pistons+Larger pads=more stopping power.

I want to go with 17" rims though so I can't BBK, too poor for 18" tires= too poor for BBK!!!! ha!

 

[Grinder34]

I'm not ready to buy off on the "more clamping power" just yet.

Right up until i boiled my brake fluid, i was always able to lock up all four wheels if i desired. I did not need any more clamping force...i had plenty.

Ghostwhite, there are BBK options that'll fit under 17" rims. ST-40 with the 332mm rotors, for example.

Not mine, but just showing heat.

 

[Ghostwhite]

Hmmmm hadn't looked far enough into that! I just know I have about a 1/4 inch gap between my current wheels and calipers.

Thanks fir the heads up :beer:

I liked to imagine clamping force as being able to more easily manipulate the brakes all the way to threshold and back without locking them up.

 

[Spamby]

I would suggest trying a more aggressive pad for the track.

Secondly, I would suggest a different brake fluid and a fresh one at that. One with a higher boiling point. Below are some stats that will help. ATE I typed the info from their site, Motul and Castrol I copied and pasted. As you can see, ATE might not cut the mustard if your really heavy on the brakes or if it moisture contaminated. A chart for ease, however the numbers are a little different than from the manufactures sites I copied and pasted. But it is still a good rep.

ATE Superblue

Dry boiling point: 536* f
wet boiling point: 388* f

Motul 600 & 660 (respectively)

600
Extremely high dry boiling point 594F(312C) helps prevent vapor lock and brake fade during hard use, with excellent recovery time. Wet boiling point 401F(205C).

660
Very high dry boiling point of 617F (325C) and a wet boiling point of 400F (204C).


AP Racing:

http://www.apracing.com/Info.aspx?InfoID=94&ProductID=41


Castrol SRF: (I like this one as it seems to have really narrowed the gap from wet to dry boiling)

• Exceptionally high dry boiling point of 590?F (Wet 518?F)

Motul RBF 660	4	617	399	Yes	16.9	MT660
AP PRF 600	4	608	311	Yes	16.9	3338-17oz
Motul RBF 600	4	594	421	Yes	16.9	MT600
Castrol SRF	4	590	518	Yes	33.8	3343-Liter
Prospeed RS683	4	583	394	Yes	16.9	3382
AP 600	n/a	572	284	* No *	16.9	3309-17oz
AP 551	3	540	284	Yes	16.9	3305-17oz
ATE Super Blue	4	536	396	Yes	33.8	3326-Liter
ATE Type 200	4	536	396	Yes	33.8	3327-Liter
Castrol LMA	4	446	311	Yes	12	3308-12oz

Racing Brake Fluid Comparison Chart
Brand Name DOT
Rating Dry
Boiling
Point Wet
Boiling
Point Compatible with
Conventional
Brake Fluids* Qty
Fl Oz Part
Number

**Copied from Pegasus Auto Racing Supplies

 

[Grinder34]

Yep, i wont disagree about fluid.

Still wondering about Calipers though. I think it mostly comes down to a few factors. In order:

1) Rotor size that can be accomidated.
2) # of pistons...even distribution of clamping force
3) caliper flex diminished in a better caliper
4) weight

but thats just guesswork on my part.

 

[Spamby]

I think your exactly correct. Those are criteria that I have always used/ understood.

Also the larger caliper holds more fluid. More fluid = cooling / clamping.

I smell a tutorial in the sticky style?? Would you agree?

 

[Spamby]

http://www.modified.com/projectcars/0409scc_project_mitsubishi_evo_vs_subaru_sti/viewall.html


A nice little read

 

[Grinder34]

http://stoptech.com/technical-suppo...ias-and-performance-why-brake-balance-matters

In all my research today I came across a graph similar to the bottom one from that paper, but for the STI and the kits they offer:

Anyone know where I could find that?