Why BBK for front only

[yomny]

Originally Posted by enwave

Different strokes for different folks, but here's my opinion on the matter:

Stopping faster shifts more weight up front, meaning there is less friction on the rear tires (less downforce/weight, less friction). For many people, especially on stock/looser suspension, you're not using the rear brakes as much. Because of that, many people don't see the need to upgrade the rear brakes. The bigger the bite in the front, the less you actually use the brakes in the back.

This can lead to some funky behavior for sure, if you're not used to driving that way. The car can become a little extra tail happy under braking, and often braking distance can actually decrease.

However, with a good stiff and flat suspension setup, you can help with some of that weight shift (a little). I think many people hit the zone where their suspension is stiff enough to help keep those back brakes doing some work, but not stiff enough to where the back brakes need more love.

If your car (theoretically) stayed perfectly flat all the time, upgrading all four is definitely necessary. In any other situation, you just need to find the right balance of front/back distribution. Once the suspension is modified, that can change very quickly. Size of the front brakes also matters. There are a lot of good articles out there about this subject if you're looking to read a little more about it.


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Thanks, makes sense. I'm really just trying to understand as to why. I always thought that with more bite in the front the transfer would be greater toward the front leaving the rear floating(stock suspension/soft damping) and making trail braking harder. Its a matter of adjusting the rebound on the rear suspension to not have the ass lift so much i guess. So with the right suspension/tires, the front brakes would usually need more power, mass to dissipate heat etc.

[Dave-ROR]

Originally Posted by yomny

Everything stated and mentioned still leaves me wondering as to why only upgrade the already bigger front disk to an even bigger one with more stopping power. I know traction is everything and nothing can substitute it, given that's constant, a front bbk only would cause more weight distribution, more ABS function and more everything.. My doubt here is, is it wise to just upgrade the front or to retain proportion and upgrade both, if money weren't a factor.

Lots of brake topics to read on the forums that cover a lot of this by the way.

First to get this out of the way, if you can lock up the tires and engage ABS you do NOT need more brake torque.

Now, the reasons for using a "BBK" are (not in order of importance):
-Consumables
-Additional thermal mass
-More efficient cooling
-In some kits, reduction in unsprung weight
-Better pad selection (depends on the car)
-Modulation/Feel (depends on the car/OEM setup)

Let's look at each of those in a bit more detail.

1. Consumables:
I did the math awhile ago and really don't feel like doing so again, but the pads in the Essex kit (which I use) are about 50% thicker and cost less than the OEM size pad. Rotors are more expensive but last significantly longer. So even though the rotor rings cost more, their durability and long life span combined with the lower cost pads and MUCH longer lifespan create a lower cost solution for those who track their cars. (pretty close to 100% worthless consideration on a street car)

2. Additional Thermal Mass:
A rotor is a piece of equipment that has multiple roles. It provides a friction surface for the pads, it connects the braking system to the hub, and thus the wheel and most importantly the tire, it dissipates heat from the braking system and most importantly it holds heat generated during braking. More thermal mass is important because it allows for repeated stops with less cool down time and prevents some heat from going to the pads and caliper. Once you extend the metals capacity for heat other components take more of it and you exceed pads thermal ranges, etc. However, this is a two way street. You can EASILY have too much thermal mass making it hard to get temps where you want them to be. This is why huge 14" rotors on these cars is just silly IMO. There are two ways to increase thermal mass, diameter and thickness and different kits go about it in different ways. Refering to the Essex Sprint kit again, it mostly increases width, this is ideal in terms of leverage staying about stock and with the caliper choice overall brake torque doesn't change much from stock, preventing bias issues.

3. Most BBKs use thicker rotors, which allows for more air to be pushed through the vents for cooling. They also use directional rotors with directional vanes. Vane count varies for the various kits. Cooling is related to one of the rotors jobs (dissipation of heat).

4. AL hats are light, calipers can be lighter. In the case of the Essex Sprint kit it's about 10lbs/front wheel (20lbs total). This is a difference that can be felt in steering and responsiveness of the front suspension.

5. Pad selection varies by car and we are lucky in that there are a bunch of WRX pads so this isn't as critical for us, however, some BBK still have better pad selection than the OEM pad choices (Wilwood superlite based kits, Essex kits, etc). Some may have worse pad selection, I haven't researched them but the only ones with worse selection are likely ebay ones.

6. Fixed calipers off better modulation and feel than sliding calipers. This is important to us as the OEM setup are sliders. The benefits here are pretty obvious.

As for the rears, you limit all of these benefits. One you don't need more thermal mass on a US or high spec overseas car. IMO the rear brakes are likely too much already, common on RWD cars with traction control. I run even pads F&R now for rotation but there's absolutely no need to increase cooling or brake torque in the rear. That is of course unless you drastically increase front brake torque (huge rotors, caliper choice, etc) then you would want to regain OEM balance or you will likely have WORSE braking performance than stock.

[CSG David]

Originally Posted by yomny

So its practical then to upgrade in this manner? I dont mind either option, just curious as to why i see it done more with this car than others. Which kits let you retain the emergency brake? Is is recommended then to use the kits with bigger discs up front?

A better question is if you're maxing out the potential of your current brakes first. These questions come up everyday. Upgrade brake pad compound and brake fluid and you are increasing the bite and heat capacity of the system.

We don't have to deal with any rear BBK upgrades as this has been deemed as a modification that does very negligible benefits to the overall package of the vehicle.

Originally Posted by yomny

I know the front does more braking hence bigger discs up front, but going to a BBK and retaining the stock rear is not the same proportion as manufacturers design.

Proper sizing of the caliper, pistons, and the overall system can actually put the brake bias within +/- 10% of the actual factory setup can help improve some braking characteristics that some may seek. This is completely up to the guys who design the braking systems. Brembo, AP, Alcon, Stoptech, Endless, Project Mu, etc. just to name a few are specialists in this field. While great questions and good concerns, you can change the bias with compound changes. Proper setup BBKs will allow you to use the same compound front and rear. We've found this to be the best brake setup to allow for better trail braking characteristics. Some people like staggered pads and that's perfectly fine.

Originally Posted by yomny

Everything stated and mentioned still leaves me wondering as to why only upgrade the already bigger front disk to an even bigger one with more stopping power. I know traction is everything and nothing can substitute it, given that's constant, a front bbk only would cause more weight distribution, more ABS function and more everything.. My doubt here is, is it wise to just upgrade the front or to retain proportion and upgrade both, if money weren't a factor.

It is not more "stopping power", but rather more thermal capacity. We maintain our brake system at such a high average temperature that we are at the absolute limit between fading and not fading, as well as, increased pad wear rate. While this may seem concerning, it's actually more of a long term cost issue for us. We go through brake pads quicker than most track guys simply because we do so much testing, training, and instruction.

When performing a cost analysis, we found that a BBK will work towards our favor. For the majority, it may or may not help them in the long term. It does offer a sense of satisfaction seeing some fat caliper behind your wheels though.

If you're local to us, we'll show you what the stock brake calipers and rotors can do (unless you're @Dave-ROR who tends to just break everything).

[Dave-ROR]

Originally Posted by enwave

Different strokes for different folks, but here's my opinion on the matter:

Stopping faster shifts more weight up front, meaning there is less friction on the rear tires (less downforce/weight, less friction). For many people, especially on stock/looser suspension, you're not using the rear brakes as much. Because of that, many people don't see the need to upgrade the rear brakes. The bigger the bite in the front, the less you actually use the brakes in the back.

This can lead to some funky behavior for sure, if you're not used to driving that way. The car can become a little extra tail happy under braking, and often braking distance can actually decrease.

However, with a good stiff and flat suspension setup, you can help with some of that weight shift (a little). I think many people hit the zone where their suspension is stiff enough to help keep those back brakes doing some work, but not stiff enough to where the back brakes need more love.

If your car (theoretically) stayed perfectly flat all the time, upgrading all four is definitely necessary. In any other situation, you just need to find the right balance of front/back distribution. Once the suspension is modified, that can change very quickly. Size of the front brakes also matters. There are a lot of good articles out there about this subject if you're looking to read a little more about it.


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You aren't stopping faster with a BBK anyways unless you couldn't engage ABS (or preferably threshold braking) with the current brake setup.

Weight transfer isn't defined by spring rates. Certainly you can make static and dynamic handling changes that may make you desire a brake configuration change (as an example I've run lower rear pads to minimize oversteer from trail braking on heavy rear roll stiffness biased FWD cars).

In a BRZ, stock or modified, equal pads are the best from what I've found so far.

[yomny]

Originally Posted by CSG David

A better question is if you're maxing out the potential of your current brakes first. These questions come up everyday. Upgrade brake pad compound and brake fluid and you are increasing the bite and heat capacity of the system.

We don't have to deal with any rear BBK upgrades as this has been deemed as a modification that does very negligible benefits to the overall package of the vehicle.



Proper sizing of the caliper, pistons, and the overall system can actually put the brake bias within +/- 10% of the actual factory setup can help improve some braking characteristics that some may seek. This is completely up to the guys who design the braking systems. Brembo, AP, Alcon, Stoptech, Endless, Project Mu, etc. just to name a few are specialists in this field. While great questions and good concerns, you can change the bias with compound changes. Proper setup BBKs will allow you to use the same compound front and rear. We've found this to be the best brake setup to allow for better trail braking characteristics. Some people like staggered pads and that's perfectly fine.



It is not more "stopping power", but rather more thermal capacity. We maintain our brake system at such a high average temperature that we are at the absolute limit between fading and not fading, as well as, increased pad wear rate. While this may seem concerning, it's actually more of a long term cost issue for us. We go through brake pads quicker than most track guys simply because we do so much testing, training, and instruction.

When performing a cost analysis, we found that a BBK will work towards our favor. For the majority, it may or may not help them in the long term. It does offer a sense of satisfaction seeing some fat caliper behind your wheels though.

If you're local to us, we'll show you what the stock brake calipers and rotors can do (unless you're @Dave-ROR who tends to just break everything).

The "stopping power" is the wrong term, picked that up from all that call of duty playing lol. Thanks, i do plan on going for the XP10 F/R with race fluid as you advised with my stock setup for starters, these will be only track pads. I really don't plan on jumping on anything major until i test my local track (homestead) and see how the car behaves at my current skill level.

[mfbmike]

Originally Posted by Dave-ROR

First to get this out of the way, if you can lock up the tires and engage ABS you do NOT need more brake torque.

Or you need better tires.



Speaking from experience with a BBK on my previous car, while driving the Dragon. Hankook V12's just weren't up to snuff.

That was fun. lol.

[mav1178]

Originally Posted by yomny

Yes sir, i've noticed a lot of them have a smaller disc in diameter up front.

example:
Front-StopTech ST-40 Red Calipers with 328x28mm Slotted Rotors
Rear-StopTech ST-22 Red Calipers with 345x28mm Slotted Rotors

Brake rotor size is not an indication of stopping power, nor an indication of which one is better.

Keep in mind that many aftermarket kits have rotors that retain the stock drum parking brake assembly. By design, this makes the rear rotors larger than the fronts if given same caliper layout as front BBKs.

-alex

[Racecomp Engineering]

Originally Posted by yomny

I know the front does more braking hence bigger discs up front, but going to a BBK and retaining the stock rear is not the same proportion as manufacturers design.

Just to touch on this for a second here...you can have a bigger rotor and LESS stopping power if you designed it a certain way. The size of the pistons in the caliper is an important variable. With most quality BBKs, you have a bigger rotor but smaller pistons and the overall brake bias remains close to stock.

A no holds barred track only car may have upgraded rear brakes but it's a good bit of extra cash that most even dedicated track guys don't need to spend. The benefit is not very large. Plus you may lose your e-brake which isn't acceptable to most that street their cars.

Dave and CSG have summed everything up pretty nicely!

- Andy

[fatoni]

Originally Posted by enwave

Different strokes for different folks, but here's my opinion on the matter:

Stopping faster shifts more weight up front, meaning there is less friction on the rear tires (less downforce/weight, less friction). For many people, especially on stock/looser suspension, you're not using the rear brakes as much. Because of that, many people don't see the need to upgrade the rear brakes. The bigger the bite in the front, the less you actually use the brakes in the back.

This can lead to some funky behavior for sure, if you're not used to driving that way. The car can become a little extra tail happy under braking, and often braking distance can actually decrease.

However, with a good stiff and flat suspension setup, you can help with some of that weight shift (a little). I think many people hit the zone where their suspension is stiff enough to help keep those back brakes doing some work, but not stiff enough to where the back brakes need more love.

If your car (theoretically) stayed perfectly flat all the time, upgrading all four is definitely necessary. In any other situation, you just need to find the right balance of front/back distribution. Once the suspension is modified, that can change very quickly. Size of the front brakes also matters. There are a lot of good articles out there about this subject if you're looking to read a little more about it.


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im fairly certain that weight transfer causes suspension compression and not the other way around so the weight transfer is happening regardless

[CSG Mike]

Originally Posted by yomny

Everything stated and mentioned still leaves me wondering as to why only upgrade the already bigger front disk to an even bigger one with more stopping power. I know traction is everything and nothing can substitute it, given that's constant, a front bbk only would cause more weight distribution, more ABS function and more everything.. My doubt here is, is it wise to just upgrade the front or to retain proportion and upgrade both, if money weren't a factor.

You're not necessarily increasing stopping power, just mass and heat dissipation (surface area/airflow).

[yomny]

Originally Posted by CSG Mike

You're not necessarily increasing stopping power, just mass and heat dissipation (surface area/airflow).

So its just braking performance increase by dissipating more heat and having more mass for friction? So the more pistons the kit has doesn't necessarily translate into more pressure/force or bite, just the force being applied over a greater contact area?

So in reality most cars out there or car owner's wallets could benefit from simply upgrading the front braking system to a BBK, as in reality the rears are sufficient for most applications. For future reference then it'll be same to assume a good front kit with maybe upgraded rear pads for the rear would suffice most of the needs of a beginner to intermidiate skilled level driver participating in HPDEs? I'll stick to the basics now, since oem power could be dealt with OEM equipment(not pads). I've been looking at some of the brake cooling solutions offered by touge factory or the APR cooling kit and they look pretty good.

[mrk1]

Originally Posted by yomny

Yes sir, i've noticed a lot of them have a smaller disc in diameter up front.

example:
Front-StopTech ST-40 Red Calipers with 328x28mm Slotted Rotors
Rear-StopTech ST-22 Red Calipers with 345x28mm Slotted Rotors

I don't believe the 345 rear kit is intended to be paired with the 328 fronts. The 345 rear would go along with the 355 fronts.

I have the 328 front kit with stock rears and love it, its about the heat capacity anyway.

[yomny]

Originally Posted by mrk1

I don't believe the 345 rear kit is intended to be paired with the 328 fronts. The 345 rear would go along with the 355 fronts.

I have the 328 front kit with stock rears and love it, its about the heat capacity anyway.

Thanks for the input

PS-also i was just looking at your fabrication progress.. man you sir are a talented human being! Continue

[raul]

Originally Posted by yomny

Everything stated and mentioned still leaves me wondering as to why only upgrade the already bigger front disk to an even bigger one with more stopping power. I know traction is everything and nothing can substitute it, given that's constant, a front bbk only would cause more weight distribution, more ABS function and more everything.. My doubt here is, is it wise to just upgrade the front or to retain proportion and upgrade both, if money weren't a factor.

Gotta break away from the bigger disc = harder braking mentality. It's mostly about cooling and longevity. Also, some BBKs are lighter than our stock brakes, which means less rotating mass, and less heat being generated. If you're paranoid about overheating your brakes, front only is enough with some good fluid and pads.