brake upgrade conundrum

[Kelse92]

Originally Posted by roastbeef

pad swaps are still sort of a pain in the ass, its not as glamorous as they make it seem. its not like putting toast in a toaster. the only benefit is you don't have to cradle a 15lb caliper once you get it off.
the bridge supports have tight tolerances and can be hard to slide in and out once they are warm and baptized in brake dust. then, you have to spread six pistons at the same time, and while you slide in one of the pads, a piston or two on the other side usually start making their way back out (anti-knockback springs doing their thing) and you have to spread the pistons again.

Lol yup, anti-knockback springs with 2mm left pads going to fresh 20mm pads swap was a PITA at the track on friday... took 40mins and missed my first session. Usually takes less time though.

[roastbeef]

Originally Posted by Captain Caveman

Don't worry. I'm having the rotors/bells made to order, so can be made in whatever size the buyer requires. They will be available in 390/380/370/360/350mm. Hope that satisfies your concerns.

i'll be blunt and honest. i'm not concerned. my brakes are squared away.

i stay out of the brake retrofit threads for a couple of reasons- i don't particularly enjoy talking down about people's side hustle, and people buying these kits are mostly concerned with aesthetics. the only reason i engaged in this conversation is the original poster talked about track performance.

there is a huge misconception that huge brakes equal high performance. rotor design is the most crucial by far, but it doesn't have much to do with the size of the rotor.
piston size and brake bias always comes up, but its rarely a real factor. i think its just something people hear, overthink, and regurgitate. i always smirk when reading posts regarding bias, but give little thought to piston ventilation, dome backed pistons, anti-knockback springs, dust boots vs piston seals, and tapered piston size for even pad squeeze. then the same people shrug their shoulders when the pads on these frankenstein kits are misaligned on the rotor by 5mm, or make crooked contact with the rotor face.

lastly, these kits are always some european company which probably consists of a few people smart enough to measure, cad, machine parts, and piece together kits, but can also disappear if one of their caliper brackets takes a complete shit and an m3 goes straight into a wall at 100+ in north america.

[Captain Caveman]

Originally Posted by roastbeef

I stay out of the brake retrofit threads for a couple of reasons- i don't particularly enjoy talking down about people's side hustle, and people buying these kits are mostly concerned with aesthetics. the only reason i engaged in this conversation is the original poster talked about track performance.

I am a designer by trade and have a logical mind, so I like to put it to use and help the M3 community where I can. I dislike the liberties taken by the big brake companies to market consumer products at enormous mark-ups, when it is clear that they sell the same, or very similar kits to car makers for a fraction of the price. I am in this primarily for myself ( I need a BBK for my car), but also to help other get better value too.

I agree that many of the retro kits banded about on here are poorly conceived, using kits of unknown provenance, normally used and repainted which may have a questionable past, and requiring the use of the standard M3 discs, which are a known weak point and kinda defeats the object as we have previously agreed.

I am trying to put together a kit that takes advantage of the research that I have done and knowledge that I have accumulated, to offer a quality option, using new, surplus high-end OE Brembo calipers and larger, thicker 2-piece discs that will resolve some of the issues experienced with the stock setup.

The kit is primarily for fast road and occasional track use, much like the Brembo GT range, and would not be recommended for very heavy track use, as that is beyond the spec of the Brembo caliper and disc material. Track/Race specific calipers have different properties such as vented pistons, no dust seals and are often lighter, more rigid, but more costly than street equivalents.

Equally, the rotor material that I will be using will be high carbon GG15, a kind of high carbon alloy which is popular in the brake disc industry. The rotors are heat treated and machined to 0.04mm and DTV to less than 0.01mm, with good physical parameters of TS to 250MPa.

This is not the absolute highest spec rotor available, but is well suited to fast road and occasional track, whilst not being an out-and-out track/race only rotor (which is much more expensive). Its increased size, combined with a 2x pad area will ensure better performance, cooler braking and less wear for the usage I have suggested, which for most is plenty enough for our needs.

[roastbeef]

i can appreciate that response and hope you are successful in producing a cost efficient, effective kit.

[ayao]

Originally Posted by roastbeef

well, forget about performance with a 390mm kit, no track guy is going to be excited about that. its going to be heavier than oem and limit wheel choices. nobody runs 19's at the track by choice.
my ap racing kit is 355mm, its 5mm smaller than oem, but weighs 10.5 lbs less per corner, for a total unsprung and rotating weight. big size isn't better.



pad swaps are still sort of a pain in the ass, its not as glamorous as they make it seem. its not like putting toast in a toaster. the only benefit is you don't have to cradle a 15lb caliper once you get it off.
the bridge supports have tight tolerances and can be hard to slide in and out once they are warm and baptized in brake dust. then, you have to spread six pistons at the same time, and while you slide in one of the pads, a piston or two on the other side usually start making their way back out (anti-knockback springs doing their thing) and you have to spread the pistons again.

100% agree with this.

[Space Fox]

Would love to hear more as well.

I'm in this same boat. Front rotors are just about shot. Torn between replacing with FCP Euro stocks so I won't have to worry about replacing ever again - or upgrading to a proper set up without the $5k+ price tag.

[roastbeef]

I'm not affiliated with this guy, but this is a deal. There is nothing better for the money.

[DRLane]

Originally Posted by roastbeef

I'm not affiliated with this guy, but this is a deal. There is nothing better for the money.

Yup, it's listed on the f8x forum.

[roastbeef]

oh crap, it won't fit then. maybe check the part number of the rotors, hats, and caliper and see if you can buy the correct brackets from essex? i don't think this is a direct fit to the e9x.

[911r]

Originally Posted by roastbeef

I'm not affiliated with this guy, but this is a deal. There is nothing better for the money.

If they were for E9x they'd be mine! Would kill for a set .. but just couldn't justify the cost for my current car considering its value. Perhaps for the next build. Looking like ST60s up front & OEM rears w/ DS2500 pads are the winners so far.

[DRLane]

Originally Posted by 911r

If they were for E9x they'd be mine! Would kill for a set .. but just couldn't justify the cost for my current car considering its value. Perhaps for the next build. Looking like ST60s up front & OEM rears w/ DS2500 pads are the winners so far.

Are you on ST60 and OEM rear now, or is this planned upgrade?

[911r]

Originally Posted by DRLane

Are you on ST60 and OEM rear now, or is this planned upgrade?

Intended upgrade once I get suspension sorted. Currently have OEM rotors all around with Cool Carbon pads, bimmerworld stainless lines & RBF 600...so not the greatest setup out there lol.

[jritt@essex]

As a general rule on the e9X chassis, you'll be far better off going with the absolute best front brake system you can afford vs. a budget system at all four corners. The front end of these cars is where the most abuse occurs by far. We see the same thing on other front engine RWD chassis as well, such as Corvettes, Camaro, Mustang, etc. We have very few e9X clients who actually have a rear brake problem. Most upgrade their rear brakes for one of a few reasons: A) Their rear brakes are trashed and they hate the idea of throwing money into OEM-style components, which will be nearly worthless at some point in the future after they're pounded upon. B) Aesthetic purposes- they want to look matchy-matchy with the fronts, as their car is a road/track hybrid use car. C) They went apesh*t and added forced induction, aero, and monster slicks, and they truly NEED more heat capacity in their rear brakes.

A properly flogged e9X M3 is going to chew through front brakes at a rate of 3-4 sets of front pads and discs for every set of rears. Again, if you have a limited budget, invest your money in the front brakes. You still should have high quality race pads in the back, and proper fluid. Otherwise, sink the money into getting the stoutest front brake system you can swing. You'll be much happier in the long run. A good quality system will also hold its value far better, and you'll get some ROI out of it when it's time to move to your next car.

[911r]

Originally Posted by jritt@essex

As a general rule on the e9X chassis, you'll be far better off going with the absolute best front brake system you can afford vs. a budget system at all four corners. The front end of these cars is where the most abuse occurs by far. We see the same thing on other front engine RWD chassis as well, such as Corvettes, Camaro, Mustang, etc. We have very few e9X clients who actually have a rear brake problem. Most upgrade their rear brakes for one of a few reasons: A) Their rear brakes are trashed and they hate the idea of throwing money into OEM-style components, which will be nearly worthless at some point in the future after they're pounded upon. B) Aesthetic purposes- they want to look matchy-matchy with the fronts, as their car is a road/track hybrid use car. C) They went apesh*t and added forced induction, aero, and monster slicks, and they truly NEED more heat capacity in their rear brakes.

A properly flogged e9X M3 is going to chew through front brakes at a rate of 3-4 sets of front pads and discs for every set of rears. Again, if you have a limited budget, invest your money in the front brakes. You still should have high quality race pads in the back, and proper fluid. Otherwise, sink the money into getting the stoutest front brake system you can swing. You'll be much happier in the long run. A good quality system will also hold its value far better, and you'll get some ROI out of it when it's time to move to your next car.

You're the man! Shooting you a PM now.

[SilverSlug]

Me likey 390mm rotors... just saying.

[W12x]

What is your thought on 6vs4 pistons front?

I am considering upgrading the front calipers/discs to BBK and keeping the rear ones stock(with matching pads). Mostly for aesthetic but also some performance.

As far as I know, other than maybe different pad choices, a good 6 pistons BBK really doesn't offer much more than a good 4, but want to see if you have any different opinion.

Originally Posted by jritt@essex

As a general rule on the e9X chassis, you'll be far better off going with the absolute best front brake system you can afford vs. a budget system at all four corners. The front end of these cars is where the most abuse occurs by far. We see the same thing on other front engine RWD chassis as well, such as Corvettes, Camaro, Mustang, etc. We have very few e9X clients who actually have a rear brake problem. Most upgrade their rear brakes for one of a few reasons: A) Their rear brakes are trashed and they hate the idea of throwing money into OEM-style components, which will be nearly worthless at some point in the future after they're pounded upon. B) Aesthetic purposes- they want to look matchy-matchy with the fronts, as their car is a road/track hybrid use car. C) They went apesh*t and added forced induction, aero, and monster slicks, and they truly NEED more heat capacity in their rear brakes.

A properly flogged e9X M3 is going to chew through front brakes at a rate of 3-4 sets of front pads and discs for every set of rears. Again, if you have a limited budget, invest your money in the front brakes. You still should have high quality race pads in the back, and proper fluid. Otherwise, sink the money into getting the stoutest front brake system you can swing. You'll be much happier in the long run. A good quality system will also hold its value far better, and you'll get some ROI out of it when it's time to move to your next car.

[jritt@essex]

Originally Posted by W12x

What is your thought on 6vs4 pistons front?

I am considering upgrading the front calipers/discs to BBK and keeping the rear ones stock(with matching pads). Mostly for aesthetic but also some performance.

As far as I know, other than maybe different pad choices, a good 6 pistons BBK really doesn't offer much more than a good 4, but want to see if you have any different opinion.

A four piston with four larger pistons can output the same brake torque as a six piston with six smaller pistons. That's not the issue. The goal of a six piston rather than a four piston is to provide greater brake pad volume. With a brake pad, volume would be length x height x thickness. Having greater pad volume spreads the heat out and provides a larger heat sink.

Here's an example. Below is the pad shape from a typical four piston front brake caliper. The friction puck of this pad is 132mm long x 51mm tall x 18mm thick.



As heat is generated during brake events, that heat travels throughout the pad...across the face of the pad, working it's way back to the backing plate, and the caliper pistons behind it. The pad has a finite ability to absorb and shed heat. All else held equal, the larger that slug of metal, the longer it takes for the heat to travel throughout the entire pad and saturate it.

Below is the pad drawing for the one used in our CP9668 six piston caliper. It is 152mm x 54mm x 25mm thick. The added volume of the six piston means it takes longer for the pad to be heat soaked. The heat is not only spread over a larger surface area (152mm x 54mm), the added thickness (25mm vs. 18mm) further insulates the caliper pistons.



The above comes into play in a few ways. First it helps prevent both fluid and pad fade. Since the heat is spread out more, the pads aren't as likely to reach their maximum operating temperature (the temp at which they can still generate friction). By slowing the transmission of heat into the pistons, the likelihood of your brake fluid boiling also goes down. All else held equal, your pad wear rates will also go up, as they're simply not burning up as fast.

The obvious next question is then, "If a bigger pad is better, why not go to a monster 8 piston caliper with a gigantic pad?" The problem with going that route is that it introduces a number of other potential issues. You ideally want the force of the caliper pistons distributed evenly across the entire back of the pad.

If the pad is too long, it becomes more prone to tapered wear, by which one end is worn down faster than the other (our six piston brake kits address that issue via differential piston bores of different sizes). If the pad is too tall, radial taper can occur, by which the top of the pad burns faster than the bottom. Also, if the pad backing plate is too long, you also run the risk of the pad material itself cracking or falling off. These are the reasons why many 8 piston calipers today use four pads per caliper rather than two. Each pad will only span two pistons. That helps prevent these issues, while also giving more leading pad edges to bite into the disc.

Also, if the pad and caliper get too large, weight becomes a problem. You don't want a huge caliper that weighs 20 lbs., nor do you want a pad that weighs 10 lbs. When you have a huge pad surface area, the disc you use is also huge. If your pad is 88mm tall rather than 54mm tall, the disc face becomes huge. Yes, it will spread the heat out over a larger area, but it will also be ridiculously heavy.

In pro racing today, we use six piston calipers on the front of just about everything. That's in IMSA, NASCAR Cup, Formula 1, and pretty much everywhere else. The six piston has proven to offer the greatest balance of heat capacity and durability while still maintaining a low weight.

Here's a Formula 1 AP Racing Radi-CAL six piston caliper:


Here's a Radi-CAL from IMSA:


Here's a NASCAR Cup six piston Radi-CAL:


Here's the CP9668 Radi-CAL we use in our M3 brake kits:


Here are the pads that the CP9668 uses. As you can see, they have enough volume absorb and disperse a lot of heat! They help keep the pad temps down, the fluid temps down, and they last a very long time. They are much more effective on a heavy, fast car than a considerably smaller pad from a four piston caliper.

[jritt@essex]

Originally Posted by W12x

What is your thought on 6vs4 pistons front?

I am considering upgrading the front calipers/discs to BBK and keeping the rear ones stock(with matching pads). Mostly for aesthetic but also some performance.

As far as I know, other than maybe different pad choices, a good 6 pistons BBK really doesn't offer much more than a good 4, but want to see if you have any different opinion.

You may want to check out our AP Racing by Essex Road Kits...might be a good fit for your needs based on your description. They have all the benefits of the large six piston pads that will last a veeeery long time, and in terms of aesthetics you won't find much better!

https://www.essexparts.com/essex-des...61380mm-bmwE90

[W12x]

jritt, thank you for the great information, and those are some beautiful looking calipers you posted.

The Radi-cal road kit is actually one of the kits I am considering, the other one is StopTech Trophy.

Originally Posted by jritt@essex

A four piston with four larger pistons can output the same brake torque as a six piston with six smaller pistons. That's not the issue. The goal of a six piston rather than a four piston is to provide greater brake pad volume. With a brake pad, volume would be length x height x thickness. Having greater pad volume spreads the heat out and provides a larger heat sink.

Here's an example. Below is the pad shape from a typical four piston front brake caliper. The friction puck of this pad is 132mm long x 51mm tall x 18mm thick.



As heat is generated during brake events, that heat travels throughout the pad...across the face of the pad, working it's way back to the backing plate, and the caliper pistons behind it. The pad has a finite ability to absorb and shed heat. All else held equal, the larger that slug of metal, the longer it takes for the heat to travel throughout the entire pad and saturate it.

Below is the pad drawing for the one used in our CP9668 six piston caliper. It is 152mm x 54mm x 25mm thick. The added volume of the six piston means it takes longer for the pad to be heat soaked. The heat is not only spread over a larger surface area (152mm x 54mm), the added thickness (25mm vs. 18mm) further insulates the caliper pistons.



The above comes into play in a few ways. First it helps prevent both fluid and pad fade. Since the heat is spread out more, the pads aren't as likely to reach their maximum operating temperature (the temp at which they can still generate friction). By slowing the transmission of heat into the pistons, the likelihood of your brake fluid boiling also goes down. All else held equal, your pad wear rates will also go up, as they're simply not burning up as fast.

The obvious next question is then, "If a bigger pad is better, why not go to a monster 8 piston caliper with a gigantic pad?" The problem with going that route is that it introduces a number of other potential issues. You ideally want the force of the caliper pistons distributed evenly across the entire back of the pad.

If the pad is too long, it becomes more prone to tapered wear, by which one end is worn down faster than the other (our six piston brake kits address that issue via differential piston bores of different sizes). If the pad is too tall, radial taper can occur, by which the top of the pad burns faster than the bottom. Also, if the pad backing plate is too long, you also run the risk of the pad material itself cracking or falling off. These are the reasons why many 8 piston calipers today use four pads per caliper rather than two. Each pad will only span two pistons. That helps prevent these issues, while also giving more leading pad edges to bite into the disc.

Also, if the pad and caliper get too large, weight becomes a problem. You don't want a huge caliper that weighs 20 lbs., nor do you want a pad that weighs 10 lbs. When you have a huge pad surface area, the disc you use is also huge. If your pad is 88mm tall rather than 54mm tall, the disc face becomes huge. Yes, it will spread the heat out over a larger area, but it will also be ridiculously heavy.

In pro racing today, we use six piston calipers on the front of just about everything. That's in IMSA, NASCAR Cup, Formula 1, and pretty much everywhere else. The six piston has proven to offer the greatest balance of heat capacity and durability while still maintaining a low weight.

Here's a Formula 1 AP Racing Radi-CAL six piston caliper:


Here's a Radi-CAL from IMSA:


Here's a NASCAR Cup six piston Radi-CAL:


Here's the CP9668 Radi-CAL we use in our M3 brake kits:


Here are the pads that the CP9668 uses. As you can see, they have enough volume absorb and disperse a lot of heat! They help keep the pad temps down, the fluid temps down, and they last a very long time. They are much more effective on a heavy, fast car than a considerably smaller pad from a four piston caliper.

Originally Posted by jritt@essex

You may want to check out our AP Racing by Essex Road Kits...might be a good fit for your needs based on your description. They have all the benefits of the large six piston pads that will last a veeeery long time, and in terms of aesthetics you won't find much better!

https://www.essexparts.com/essex-des...61380mm-bmwE90