Best retrofit for M3 brakes?

[tdott]

Originally Posted by Space Fox

How far off are we talking? Would paired w f8x rear calipers help bring the bias back in to an acceptable range?

calculations were posted a few pages back

[bbnks2]

Originally Posted by Torgus

Too bad people never worry about it. But hey big flashy calipers, at least they look like they should stop faster.

lol you're preaching to people putting BBK on their car just to run ebc yellow stuff.

First step before all this should be fitting proper brake ducts and a real track pad that is more true to it's rating.

[Space Fox]

Originally Posted by tdott

calculations were posted a few pages back

I'm not seeing any calcs for the C63 front calipers w F8x rears. I don't see how this could be that far off from a 6 pot front BBK offered by multiple manufacturers. Forgive my ignorance I am far from an expert on brake retrofits, bias, and piston size. Just looking for a cost effective upgrade in braking that is also safe to use on track. Yes, a used BBK would probably be best but those are few and far between.

[Torgus]

Originally Posted by Space Fox

Yes, a used BBK would probably be best but those are few and far between.

There is are 3-4 used BBKs and 1 set of brake ducts in the for sale section 1st page in for sale section:

https://www.m3post.com/forums/showthread.php?t=1860088

https://www.m3post.com/forums/showthread.php?t=1851949

[ygoz]

Originally Posted by Space Fox

I'm not seeing any calcs for the C63 front calipers w F8x rears. I don't see how this could be that far off from a 6 pot front BBK offered by multiple manufacturers. Forgive my ignorance I am far from an expert on brake retrofits, bias, and piston size. Just looking for a cost effective upgrade in braking that is also safe to use on track. Yes, a used BBK would probably be best but those are few and far between.

There are calculations for this in the thread.
Calipers size and amount of pistons is once things, but another crucial factor is the surface area of the pistons themselves.

For C63 AMG callipers see - https://www.m3post.com/forums/showpo...4&postcount=35

[S55_M3]

Just finished my f8x retrofit, thanks to tdott for his diy.

[SilverSlug]

Originally Posted by S55_M3

Just finished my f8x retrofit, thanks to tdott for his diy.

Looks perfect. Btw what suspension are you running?

[S55_M3]

Originally Posted by SilverSlug

Looks perfect. Btw what suspension are you running?

Thank you, h&r springs on edc suspension

[drwankel]

Originally Posted by S55_M3

Just finished my f8x retrofit, thanks to tdott for his diy.

Are you running spacers or not? Ebrake behaves like expected? Which f8x brake setup did you use for the retrofit?

[S55_M3]

Originally Posted by drwankel

Are you running spacers or not? Ebrake behaves like expected? Which f8x brake setup did you use for the retrofit?

No spacers, although I plan to run a 10mm on the rear just for appearances. E brake works as designed. These are the steel brakes from an f80

[tdott]

Originally Posted by S55_M3

Just finished my f8x retrofit, thanks to tdott for his diy.

Awesome, they look great!

Let us know how they feel once you've had a chance to test them out.

[WagonR]

Sorry if this has been answered before, or I just don't understand things correctly, but if an expert can help me answer the following it would be appreciated.

My understanding is that the problem with retrofit brake kits is that they're not designed for the car. Most common would be putting some 8 piston caliper off of a Lambo with some 380mm disks from a F8X onto the front of a E9X and you're going to have issues with brake balance and peddle feel. That seems to make sense to me, the larger rotor and higher force of the 8 piston caliper will presumably increase braking in the front and that massive caliper and all of its pistons will have way more fluid going through it, thus impacting peddle feel.

To me, this makes me thing you'd want a big brake setup from the popular brands (Brembo, Stoptech, etc.) designed for the car. However, I wonder what's actually designed for the car...

Does Stoptech have different calipers for each kit? If I go with a ST40 for my M3, is that the same caliper I had on my WRX ST40 Stoptech BBK? I think it probably is. Sure the bracket and disk are different, but it's not like they're playing with piston size to balance braking, right? Similar thoughts with Brembo, how many versions of their calipers are they making? Is the caliper in a E9X M3 brake kit from Brembo any different than the caliper from a Focus RS or Alfa, or AMG or whatever?

As an example, Brembo offers a 6 piston caliper 380mm rotor front brake setup. If I can source the caliper off of any car offered with it from the factory, run F8X 380mm rotors, and use a bracket to position the caliper correctly, what exactly is different form the kit Brembo offers?

[tdott]

Originally Posted by WagonR

Sorry if this has been answered before, or I just don't understand things correctly, but if an expert can help me answer the following it would be appreciated.

My understanding is that the problem with retrofit brake kits is that they're not designed for the car. Most common would be putting some 8 piston caliper off of a Lambo with some 380mm disks from a F8X onto the front of a E9X and you're going to have issues with brake balance and peddle feel. That seems to make sense to me, the larger rotor and higher force of the 8 piston caliper will presumably increase braking in the front and that massive caliper and all of its pistons will have way more fluid going through it, thus impacting peddle feel.

To me, this makes me thing you'd want a big brake setup from the popular brands (Brembo, Stoptech, etc.) designed for the car. However, I wonder what's actually designed for the car...

Does Stoptech have different calipers for each kit? If I go with a ST40 for my M3, is that the same caliper I had on my WRX ST40 Stoptech BBK? I think it probably is. Sure the bracket and disk are different, but it's not like they're playing with piston size to balance braking, right? Similar thoughts with Brembo, how many versions of their calipers are they making? Is the caliper in a E9X M3 brake kit from Brembo any different than the caliper from a Focus RS or Alfa, or AMG or whatever?

As an example, Brembo offers a 6 piston caliper 380mm rotor front brake setup. If I can source the caliper off of any car offered with it from the factory, run F8X 380mm rotors, and use a bracket to position the caliper correctly, what exactly is different form the kit Brembo offers?

Read a few pages back about piston size and piston area of various calipers.

All 6 piston calipers are not created equal. You are missing a key point. Piston sizes/ total piston area.

[WagonR]

Originally Posted by tdott

Read a few pages back about piston size and piston area of various calipers.

All 6 piston calipers are not created equal. You are missing a key point. Piston sizes/ total piston area.

I don't think I'm missing the point about piston size and total piston areas; I thought I acknowledged that on the front end of my post. My point was that Brembo makes a 6 piston caliper that they sell to OEMs and on their BBKs. Do they have 100s of them that while looking the same on the outside, that have different piston sizes to match all of the cars they sell stuff for, or not? Or is it just a couple and they use what fits the most. Or is it all just one caliper?

I guess the question is, is the 6 piston caliper from this https://www.turnermotorsport.com/p-341463-tms341463/ any different than other 6 piston calipers Brembo sells? Like this one for a Golf R https://www.uspmotorsports.com/Bremb...mm-Yellow.html

[jritt@essex]

Originally Posted by WagonR

I don't think I'm missing the point about piston size and total piston areas; I thought I acknowledged that on the front end of my post. My point was that Brembo makes a 6 piston caliper that they sell to OEMs and on their BBKs. Do they have 100s of them that while looking the same on the outside, that have different piston sizes to match all of the cars they sell stuff for, or not? Or is it just a couple and they use what fits the most. Or is it all just one caliper?

I guess the question is, is the 6 piston caliper from this https://www.turnermotorsport.com/p-341463-tms341463/ any different than other 6 piston calipers Brembo sells? Like this one for a Golf R https://www.uspmotorsports.com/Bremb...mm-Yellow.html

WagonR,
The answer to your question is yes, and you are spot-on with your concerns and assessment. While six piston calipers from the same manufacturer may in some cases look the same on the outside, they may have dramatically different piston sizes and resulting brake torque output.

For example, in our rear AP Racing Radi-CAL Brake Kits, we use a caliper CP944x. Depending on the chassis to which we are applying the brake system, we use different variants with different piston sizes. That ensures that the proper brake torque is generated at that end of the car when combined with the brake disc we select. When combined with a wide array of disc sizes, that allows us to dial in the brake torque to very closely match the OEM settings. That means a smooth integration with the vehicle electronics such as ABS, EBD, etc. The car essentially doesn't know anything has changed at the wheel end.

Below are some different iterations of this caliper and their piston sizes. 95% of the members on this forum would not be able to recognize the difference between these calipers by their outward appearance. The only way to differentiate them would be by looking at the pistons (which you can't see when mounted), or a few other small clues if you know what you're looking for.

CP9448- 38.1/41.3mm
CP9449- 29/34mm
CP9450- 27/32mm
CP9451- 25.4/28.6mm

Then there are a couple other variants with a slightly larger mounting pattern...like this one for example:
CP9446- 34.9/41.3mm

As you probably noted when looking at the list above, the difference in piston sizes on the above AP calipers is tremendous. If you held your disc sizes equal, pad compound the same, and put a caliper variant from the wrong end of the size spectrum on the back of your car (a 38/41mm version rather than a 25/28mm version), your braking performance would be significantly degraded, and be absolutely far worse than stock. Your ABS would go bonkers, and if you didn't have ABS, your car would be constantly trying to swap ends on you under braking.
That's why randomly throwing brake components from a different car onto your car is a bad idea. Some of these 'retrofit kits' attempt to take the piston sizes into account, but at the same time they are fouling up the brake torque because they're applying the calipers to discs of a considerably different effective radius than what came stock on your car. While they may look cooler than the boring stock brakes, a Frankenstein 'brake kit' is a recipe for poor performance, longer stopping distances, premature ABS intervention, etc. That doesn't even take into account the quality of the other system components, such as the caliper adapter brackets. Over the years we've seen some horrendous quality, failures, cracks, etc.

This video we put together a couple years ago may make things a bit clearer on how we choose the components for a brake kit application:

[Torgus]

Originally Posted by jritt@essex

That's why randomly throwing brake components from a different car onto your car is a bad idea. Some of these 'retrofit kits' attempt to take the piston sizes into account, but at the same time they are fouling up the brake torque because they're applying the calipers to discs of a considerably different effective radius than what came stock on your car. While they may look cooler than the boring stock brakes, a Frankenstein 'brake kit' is a recipe for poor performance, longer stopping distances, premature ABS intervention, etc. That doesn't even take into account the quality of the other system components, such as the caliper adapter brackets. Over the years we've seen some horrendous quality, failures, cracks, etc.

This.

Why this is hard to understand I don't get it. Yet everyone continually puts on fancy looking calipers diminishing their braking ability and or causing other issues.

[tdott]

Originally Posted by WagonR

I don't think I'm missing the point about piston size and total piston areas;

You never once mentioned piston size or area in your question why aren't all 6 pistons the same.

Originally Posted by WagonR

As an example, Brembo offers a 6 piston caliper 380mm rotor front brake setup. If I can source the caliper off of any car offered with it from the factory, run F8X 380mm rotors, and use a bracket to position the caliper correctly, what exactly is different form the kit Brembo offers?

As I said, and jritt from essex also said, you can't just source any 6 piston Brembo caliper from a random car and put it on like you were asking and expect it to be an improvement.

So yes, you totally missed the point.

[WagonR]

Originally Posted by tdott

You never once mentioned piston size or area in your question why aren't all 6 pistons the same.



As I said, and jritt from essex also said, you can't just source any 6 piston Brembo caliper from a random car and put it on like you were asking and expect it to be an improvement.

So yes, you totally missed the point.

If I’m saying the exterior of the same calipers all look the same, what ELSE would I be asking about besides the pistons? Sure, could have been more clear, but wow guy, what’s your axe to grind here?

Second, I was never advocating for piecing together a random brake kit. So maybe chill on the belittling? I mean honestly, do you feel better now?

The fist thing I said was that I knew that sourcing a random caliper and rotor that physically fit was bad because it could/would mess up brake bias and pedal feel. I guess I wasn’t explicit in listing the reasons that would be bad (leverage and piston size), but I certainly wasn’t advocating for it.

I was just looking at the offerings, let’s say a ST40, and wondering if that caliper has 1, 5 or 100 versions. Is the caliper in a WRX front kit the same as one in a M3 E36, E46 and E90 font brake kit? What about the rear ST40 kit. I’d presume so, but I don’t have access to a bunch of calipers to measure or check.

I get that essex is a vendor so they’re not going to call me an idiot like you did, but they seemed to understand my question.

I’m still confused on what your issue is. I saw that manufacturers seemed to offer a lot of brake kits (aftermarket and OEM) and wondered if they make each specific caliper for each application, have a range of calipers that they best fit to the application or if they roll with one or a just few. I was curious and asked a question.

[WagonR]

Originally Posted by jritt@essex

WagonR,
The answer to your question is yes, and you are spot-on with your concerns and assessment. While six piston calipers from the same manufacturer may in some cases look the same on the outside, they may have dramatically different piston sizes and resulting brake torque output.

For example, in our rear AP Racing Radi-CAL Brake Kits, we use a caliper CP944x. Depending on the chassis to which we are applying the brake system, we use different variants with different piston sizes. That ensures that the proper brake torque is generated at that end of the car when combined with the brake disc we select. When combined with a wide array of disc sizes, that allows us to dial in the brake torque to very closely match the OEM settings. That means a smooth integration with the vehicle electronics such as ABS, EBD, etc. The car essentially doesn't know anything has changed at the wheel end.

Below are some different iterations of this caliper and their piston sizes. 95% of the members on this forum would not be able to recognize the difference between these calipers by their outward appearance. The only way to differentiate them would be by looking at the pistons (which you can't see when mounted), or a few other small clues if you know what you're looking for.

CP9448- 38.1/41.3mm
CP9449- 29/34mm
CP9450- 27/32mm
CP9451- 25.4/28.6mm

Then there are a couple other variants with a slightly larger mounting pattern...like this one for example:
CP9446- 34.9/41.3mm

As you probably noted when looking at the list above, the difference in piston sizes on the above AP calipers is tremendous. If you held your disc sizes equal, pad compound the same, and put a caliper variant from the wrong end of the size spectrum on the back of your car (a 38/41mm version rather than a 25/28mm version), your braking performance would be significantly degraded, and be absolutely far worse than stock. Your ABS would go bonkers, and if you didn't have ABS, your car would be constantly trying to swap ends on you under braking.
That's why randomly throwing brake components from a different car onto your car is a bad idea. Some of these 'retrofit kits' attempt to take the piston sizes into account, but at the same time they are fouling up the brake torque because they're applying the calipers to discs of a considerably different effective radius than what came stock on your car. While they may look cooler than the boring stock brakes, a Frankenstein 'brake kit' is a recipe for poor performance, longer stopping distances, premature ABS intervention, etc. That doesn't even take into account the quality of the other system components, such as the caliper adapter brackets. Over the years we've seen some horrendous quality, failures, cracks, etc.

This video we put together a couple years ago may make things a bit clearer on how we choose the components for a brake kit application:

Really appreciate the response. I don’t know how this came across as me advocating for some Frankenstein brake kit, was really just interested in how much customization was really occurring at the manufacturer level. You provided some great insights to that. Again, appreciate the time/insight.

[tdott]

Originally Posted by WagonR

If I’m saying the exterior of the same calipers all look the same, what ELSE would I be asking about besides the pistons? Sure, could have been more clear, but wow guy, what’s your axe to grind here?

Second, I was never advocating for piecing together a random brake kit. So maybe chill on the belittling? I mean honestly, do you feel better now?

No, I do not feel better. Helping someone that can't be helped never feels good, sorry I tried.

I pointed out where to look for the answers of your question in my first reply to you and what to look for. It seems to have went over your head.

My second reply reiterated that, and supported jritt's reply to spoon feed you information which was discussed earlier in this tread.

I apologize if I made you feel or your question seem "unimportant" or belittled.

[edsonreds]

Originally Posted by jritt@essex

WagonR,
The answer to your question is yes, and you are spot-on with your concerns and assessment. While six piston calipers from the same manufacturer may in some cases look the same on the outside, they may have dramatically different piston sizes and resulting brake torque output.

For example, in our rear AP Racing Radi-CAL Brake Kits, we use a caliper CP944x. Depending on the chassis to which we are applying the brake system, we use different variants with different piston sizes. That ensures that the proper brake torque is generated at that end of the car when combined with the brake disc we select. When combined with a wide array of disc sizes, that allows us to dial in the brake torque to very closely match the OEM settings. That means a smooth integration with the vehicle electronics such as ABS, EBD, etc. The car essentially doesn't know anything has changed at the wheel end.

Below are some different iterations of this caliper and their piston sizes. 95% of the members on this forum would not be able to recognize the difference between these calipers by their outward appearance. The only way to differentiate them would be by looking at the pistons (which you can't see when mounted), or a few other small clues if you know what you're looking for.

CP9448- 38.1/41.3mm
CP9449- 29/34mm
CP9450- 27/32mm
CP9451- 25.4/28.6mm

Then there are a couple other variants with a slightly larger mounting pattern...like this one for example:
CP9446- 34.9/41.3mm

As you probably noted when looking at the list above, the difference in piston sizes on the above AP calipers is tremendous. If you held your disc sizes equal, pad compound the same, and put a caliper variant from the wrong end of the size spectrum on the back of your car (a 38/41mm version rather than a 25/28mm version), your braking performance would be significantly degraded, and be absolutely far worse than stock. Your ABS would go bonkers, and if you didn't have ABS, your car would be constantly trying to swap ends on you under braking.
That's why randomly throwing brake components from a different car onto your car is a bad idea. Some of these 'retrofit kits' attempt to take the piston sizes into account, but at the same time they are fouling up the brake torque because they're applying the calipers to discs of a considerably different effective radius than what came stock on your car. While they may look cooler than the boring stock brakes, a Frankenstein 'brake kit' is a recipe for poor performance, longer stopping distances, premature ABS intervention, etc. That doesn't even take into account the quality of the other system components, such as the caliper adapter brackets. Over the years we've seen some horrendous quality, failures, cracks, etc.

This video we put together a couple years ago may make things a bit clearer on how we choose the components for a brake kit application:

Originally Posted by jritt@essex

WagonR,
The answer to your question is yes, and you are spot-on with your concerns and assessment. While six piston calipers from the same manufacturer may in some cases look the same on the outside, they may have dramatically different piston sizes and resulting brake torque output.

For example, in our rear AP Racing Radi-CAL Brake Kits, we use a caliper CP944x. Depending on the chassis to which we are applying the brake system, we use different variants with different piston sizes. That ensures that the proper brake torque is generated at that end of the car when combined with the brake disc we select. When combined with a wide array of disc sizes, that allows us to dial in the brake torque to very closely match the OEM settings. That means a smooth integration with the vehicle electronics such as ABS, EBD, etc. The car essentially doesn't know anything has changed at the wheel end.

Below are some different iterations of this caliper and their piston sizes. 95% of the members on this forum would not be able to recognize the difference between these calipers by their outward appearance. The only way to differentiate them would be by looking at the pistons (which you can't see when mounted), or a few other small clues if you know what you're looking for.

CP9448- 38.1/41.3mm
CP9449- 29/34mm
CP9450- 27/32mm
CP9451- 25.4/28.6mm

Then there are a couple other variants with a slightly larger mounting pattern...like this one for example:
CP9446- 34.9/41.3mm

As you probably noted when looking at the list above, the difference in piston sizes on the above AP calipers is tremendous. If you held your disc sizes equal, pad compound the same, and put a caliper variant from the wrong end of the size spectrum on the back of your car (a 38/41mm version rather than a 25/28mm version), your braking performance would be significantly degraded, and be absolutely far worse than stock. Your ABS would go bonkers, and if you didn't have ABS, your car would be constantly trying to swap ends on you under braking.
That's why randomly throwing brake components from a different car onto your car is a bad idea. Some of these 'retrofit kits' attempt to take the piston sizes into account, but at the same time they are fouling up the brake torque because they're applying the calipers to discs of a considerably different effective radius than what came stock on your car. While they may look cooler than the boring stock brakes, a Frankenstein 'brake kit' is a recipe for poor performance, longer stopping distances, premature ABS intervention, etc. That doesn't even take into account the quality of the other system components, such as the caliper adapter brackets. Over the years we've seen some horrendous quality, failures, cracks, etc.

This video we put together a couple years ago may make things a bit clearer on how we choose the components for a brake kit application:

Thank you for sharing your knowledge!

I understand that you work for that company, very well known among car enthusiasts.

I dont want to be rude, but It would seem very strange you could advocate towards a "frankenstein" brake set up, given commercial conflict of interests.

But I may be mistaken. Would you be able to advice members of this thread which calipers could reasonably work for the E9X M3 if we go the route of frankesteining our brakes?

Regards!

[Power6]

Hi BMW people, this is non-sequitar I'm just a random nobody with a Volvo but these forums have been so helpful when researching calipers, I wanted to give back!

I created a calculator that can get you close to proper sizing of brakes if you are going to mix and match your own components. Should save one a lot of time in looking at different setups quickly, or checking on the design of a brake kit, there are plenty of badly engineered kits out there.

It's here: https://upbrakes.com/upgrade_advisor

Should be pretty straightforward, you need to know a little info; rotor size, piston sizes and the pad depth. That gets you very close to reality. Common Brembo sizes are known depth pads, the 6 piston OEM type Brembos you guys are usually looking at like D1116 is 55mm, or D1666 is 65mm. Others you may have to measure yourself. Pad depth is often overlooked as a factor but it matters. If rotor size and piston sizes are accounted for. You can often change say the 55mm pad out for a 65mm annulus if you can fit it, or vice versa, to bring torque output into line.

The calculator outputs and compares individual axle torque output. Matching by simple bias is an outdated way to design. The electronic brake features are way beyond just ABS and all depend on a particular torque output for a given pressure input at each corner within reason for systems that are designed to still work with variable parts and maintenance. All the modern era BMWs using the Mk60 and newer ABS hardware, they use EBD to proportion. There is a base curve but each wheel is being monitored for slip conditions and adjusted accordingly on 4 channels, for best dynamic performance, long before any ABS intervention. Matching torque output keeps it all working well.

Generally you want to size up the rotor, size down the piston area and strike the right balance to match by carefully choosing the specifics. The side effect is reduced pedal travel and better feel. As cars go electro-hydraulic "brake-by-wire" you can't change the pedal feel, but matching the pressure/torque output becomes even more critical as the electronic brake unit now performs 100% of the braking action.

Hope this is helpful to some peeps out there.