School me on BMW/Porsche brake upgrade options.

[m3f_Cha5en_0f07ac6b17]

Maybe a better explanation is needed... With a BBK you have less surface area that is clamping but you are covering more of the rotor.


I'm not sure I explained that well.. Basically if you grabbed a moving wheel with ONE large hand in ONE place it would be harder to stop it than if you used 4 smaller hands but spaced out and covering more of the circumference.


I hope my explanation helped you out on that one WRX. I am not an engineer but I understand the physics of it.

[m3f_98_1LE_d72735c149]

Area is what is important, and mathematically a 70mm piston has an area of 3848 mm^2.


A 35mm piston has an area of 962. (cut the diameter in half, the area is cut to 1/4)


That said, two pistons with a combined total area of 3848 will apply the same force as one piston with the same area.


The reason we want more pistons, especially with larger pad areas, is the forces are spread out and tend to wear much more evenly (e.g. no pad taper).


The reason we want more rotor than is needed to lock up the brakes is during hard driving, we need somewhere for the heat to go so we don't overheat the pads, fluid, rotors etc. Large rotors with more mass are a better heat sink. Having unswept pad area, especially to the inside, helps keep heat away from wheel bearings. As an engineer I am sure you can understand what happens to the grease when it overheats, or the seals, which then allow the grease a path out and dirt a path in....


Bottom line is no one wants to add unsprung rotating weight, especially when it is expensive. If you only drive on the street and follow the laws for the most part, stock brakes are fine. Stock brakes with better pads/fluid is fine for autocross, and beginner HPDE. But as you get faster and move up to R compounds on a road course, the limitations of even good stock brakes like the M3 has quickly make life hell.


EDIT: For the most part, OEM ABS systems will fix and bias issues created by adding front brake.

[m3f_OahuMPower_17503f01cd]

This.



Although 6 piston calipers do have their drawbacks, which is why I will be going with a 4 piston variant when the time comes.



yep, TOO many pistons, and you start to lose the effectiveness as well.



Would I love to get a 4 piston PFC kit, hell yeah, but I dont have that kind of money. The wilwood 4 piston kit is a great kit, that had a lot of engineering put into it to make sure the brake bias didnt change, and the brake torque was increased. You also have to realize that a BBK is fixed mounted, not a floating system such as OEM, and that also helps with brake feel, brake fade, even distribution of brake torque over the entire fad, etc.



An oem floating brake system sometimes binds up, and you wear one side of the pad more than the other. Do you think you are getting full brake torque over the surface area of the pad? NO.



There are many other benefits to a BBK, besides the weight factor to consider :rulaiz:

[m3f_camdinans3_bfa1f49a41]

i want a bbk but i don't need it at all and i don't want to get something just for appearance sake.


i've got euro floaters and some better pads and it will be more than i need with my current suspension, tire/wheel setup. Although i think its awesome currently.

[m3f_Richardspe_ff9fba485e]

I didn't need the BBK, just like I didn't need the BBS wheels. But Damn! It does look cool...



I got the 6 piston calipers because of the better clearance with my 17" BBS wheels. No I wasn't going to spend $4K plus for 18" BBS wheels and tires.



Plus I got a great discount from Rob on the kit.

[m3f_WRXEATR_c6f1d80be6]

FWIW I just discovered that euro spec e38 7 series 4 pot brembos bolt up to our spindles as well with a 4.75" mounting center. The caliper size used is 316mm which means they can be used with our e36 euro motorsport floating rotors.



http://www.m3forum.net/m3forum/showthread.php?t=303202

[m3f_ozzM3_bf7a436f50]

+1 Very well said, also when choosing BBK don't forget to check a spectrum of brake pads that are readily available for the particular caliper type.



It is very important for us, track rats :goodluck:







Area is what is important, and mathematically a 70mm piston has an area of 3848 mm^2.



A 35mm piston has an area of 962. (cut the diameter in half, the area is cut to 1/4)



That said, two pistons with a combined total area of 3848 will apply the same force as one piston with the same area.



The reason we want more pistons, especially with larger pad areas, is the forces are spread out and tend to wear much more evenly (e.g. no pad taper).



The reason we want more rotor than is needed to lock up the brakes is during hard driving, we need somewhere for the heat to go so we don't overheat the pads, fluid, rotors etc. Large rotors with more mass are a better heat sink. Having unswept pad area, especially to the inside, helps keep heat away from wheel bearings. As an engineer I am sure you can understand what happens to the grease when it overheats, or the seals, which then allow the grease a path out and dirt a path in....



Bottom line is no one wants to add unsprung rotating weight, especially when it is expensive. If you only drive on the street and follow the laws for the most part, stock brakes are fine. Stock brakes with better pads/fluid is fine for autocross, and beginner HPDE. But as you get faster and move up to R compounds on a road course, the limitations of even good stock brakes like the M3 has quickly make life hell.





EDIT: For the most part, OEM ABS systems will fix and bias issues created by adding front brake.

[m3f_OahuMPower_17503f01cd]

+1 Very well said, also when choosing BBK don't forget to check a spectrum of brake pads that are readily available for the particular caliper type.



It is very important for us, track rats :goodluck:



this.... I need to have plenty of track pad choices, and while a cheap Brembo bbk option looks inviting, the same 315mm rotor choice (not bigger rotors to help with heat dissipation, lack of pad choice, and probably heavier calipers) sway me HEAVILY to stay away from the "oem bbk option"



How many track pad choices do you think there are for an e38 7 series?

[m3f_WRXEATR_c6f1d80be6]

this.... I need to have plenty of track pad choices, and while a cheap Brembo bbk option looks inviting, the same 315mm rotor choice (not bigger rotors to help with heat dissipation, lack of pad choice, and probably heavier calipers) sway me HEAVILY to stay away from the "oem bbk option"


How many track pad choices do you think there are for an e38 7 series?


Just as many as there are for the 8 series. Its a shared pad size with many models. They're actually a very common pad.


they're 65 bucks.


http://www.streetsideauto.com/products.asp?ptid=5632&brand=BHCD&series=HPS%20Per formance%20Street&partnumber=HB181F.660&Skip=True& LookupType=YMM&Reset=True&utm_source=GoogleShoppin g&utm_medium=GoogleShopping&utm_term=GoogleShoppin g&utm_content=GoogleShopping&utm_campaign=GoogleSh opping


Put it into google:


http://www.google.com/#hl=en&q=HB181F.660&aq=f&aqi=&oq=&fp=e8d6ef47431c6 a4a


18,500 results doesn't seem that rare to me. :clueless:

[m3f_OahuMPower_17503f01cd]

what track pad options do I have?



and why would you still want a 315mm rotor on a bbk? that defeats the purpose of getting a BBK with bigger rotors for heat dissipation :clueless:

[m3f_ozzM3_bf7a436f50]

I was just surfing the net a bit and answer in no - no track pad options for

this type of E38 caliper, just performance street ones.



But, nice project in any case, OP is not tracking his car.





what track pad options do I have?



and why would you still want a 315mm rotor on a bbk? that defeats the purpose of getting a BBK with bigger rotors for heat dissipation :clueless:

[m3f_WRXEATR_c6f1d80be6]

what track pad options do I have?


and why would you still want a 315mm rotor on a bbk? that defeats the purpose of getting a BBK with bigger rotors for heat dissipation :clueless:


What kind of pad would yo like? Below is the entire line of Hawk pads for this caliper, and this was just my first search I conducted. I'm sure if you looked some could be found. This is the same pad used in the Nissan GTR and many Lamborghinis. There HAS to be something out there....


Here's a list of all cars that use this same pad:


http://www.ebcbrakesdirect.com/search/default.asp?part=DP31032C&v1=car&t1=&x=45&y=7


Click on the white box pull down arrow.


I was just surfing the net a bit and answer in no - no track pad options for

this type of E38 caliper, just performance street ones.


But, nice project in any case, OP is not tracking his car.


I wouldnt say that just yet. This is the very first search I did for track pads for this caliper:


http://www.placeforbrakes.com/products.php?car_model_key=30061&car_year=1997&cat egory_key=9


EVERY one of Hawk's pad compounds are available for this caliper. HP, HP+, BLUE, DC-70/60, etc, etc.

[m3f_ozzM3_bf7a436f50]

That is exactly the problem when you need a track pad - many BBKs has very limited choice of really aggressive pad compound, Stoptech calipers

seems to be a way to go in this respect.


And yes, you are correct - Hawk HT 10 are available, but no PFC or Carbotech.


ahhh....I see what you mean. I'm sure if you looked some could be found. This is the same pad used in the Nissan GTR and many Lamborghinis. There HAS to be something out there....


Here's a list of all cars that use this same pad:


http://www.ebcbrakesdirect.com/search/default.asp?part=DP31032C&v1=car&t1=&x=45&y=7


Click on the white box pull down arrow.


I wouldnt say that just yet. This is the very first search I did for track pads for this caliper:


http://www.placeforbrakes.com/products.php?car_model_key=30061&car_year=1997&cat egory_key=9


EVERY one of Hawk's pad compounds are available for this caliper. HP, HP+, BLUE, DC-70/60, etc, etc.

[m3f_Obioban_3ce2570049]

I posted this in the other thread, but it seems like it mentions some points that haven't been brought up here:


Is there any actual reason to do this? As in, if the piston volume is not identical to stock, front and rear (HIGHLY unlikely), you're going to make stopping distance and pedal feel worse. In exchange you're gaining bling and heat capacity.


The e36's stock brakes are pretty damn good. Are any of you fading them on the street using street or on the track using track pads (and yes, track pads will still be needed on the track with these).


I feel like this mod is sacrificing braking performance for bling. If it were me, I'd stick with stick till I could afford a system that was designed to work on the car.


Even heat capacity you're not gaining that much of, as it's the same size rotor... So you're just gaining pad capacity... Which isn't that useful...

[m3f_ozzM3_bf7a436f50]

That's actually interesting point, did you try to compare contact area size of OEM brake pad and pad from e38 caliper? 4 pistons are fine, but what else you'll gain?