[Blue Angel]

OK, so I looked into these 19Z calipers a little closer. Turns out they have 36mm pistons, all the same size (not staggered like many do). This means they have 10% more clamping force than the G-Series calipers (40/44mm) and E70 X5M (42/42mm), and 16% more clamping force than M5 calipers. This is not a good thing, this is bad as it will lead to a more front-biased brake force distribution (rear brakes will have less braking torque when the fronts lock up). This means longer stopping distances and more wear/heat in the front brakes vs. the rears.

So the disadvantages in using a 19Z caliper on a 5-Series compared to the G-Series calipers are:

1. Narrower pads that don't cover the surface of BMW 374mm rotors (they are commonly sold with brake upgrade kits using 380mm rotors). This can be seen in the assembly pictures posted above, and the outside of the pad may go past the outside of the rotor by a few mm

2. Symmetrical pistons that could lead to tapered pad wear (BMW G-Series calipers use 40/44mm pistons). To be fair, the E70 X5M calipers also use symmetrical 42mm pistons

3. 10%/16% more piston area (clamping force) compared to G-Series/F10 M5 calipers (respectively) which will cause a forward braking bias, increasing stopping distances and adding more heat to the front brakes (reduced rear braking). Add the narrow pad design that's biased more to the outside of the rotor and this situation gets worse

4. Require custom brackets to mount to F10 spindle. May not be an issue, but more parts introduce more points of possible failure, and custom brackets have not been through testing validation. Probably not an issue, but a data point none-the-less

5. Visually will be nearly identical in size to the 374mm version of the G-Series caliper (they both wrap around a similarly sized rotor)

6. G-Series calipers are cut to accept small wheels. The 374mm caliper has been shown to clear some 18" OEM BMW wheels, maybe some aftermarket also. Lots of clearance for 19" wheels

7. G-Series caliper use very wide pads, allowing the use of the small diameter hat version of the 374mm rotor from the F01 760. This adds much more swept area

8. The finish on a custom 19Z caliper may not be as durable as the factory finish on a G-Series caliper if you find an original blue caliper from an MS Brake equipped car. If you're painting yourself it's a tossup

The one advantage I could possibly see on the 19Z caliper is it could potentially have better spoke clearance for wheels. I say potentially only because the G-Series caliper has shown to be tight on some wheels, requiring the use of a spacer. I have no idea if the 19Z is any better or not as I haven't tried one.

For all the reasons I state above, my personal opinion is an F10 owner should try to use one of the proven upgrade routes with BMW calipers if possible before looking to calipers from other brands. Numbers 1-3 above will be issues if you are using 374mm BMW replacement rotors. #3 might not be an issue if you are using an upgraded rear caliper as well, but to know for sure you will have to look at piston diameters, rotor dimensions, pad fit, and pad effective radius to determine whether you are negatively affecting your brake bias or not.

Sorry for sounding so negative dentprotony, but I just want people to know wheat they're getting into should they choose to upgrade.

To anyone thinking of upgrading, please check out this thread where most of your options are thoroughly explored and tested:

https://f10.5post.com/forums/showthread.php?t=1488894

It's a ton of reading, but it will be worth it if you decide to go ahead with an upgrade.

[dentprotony@gmail.com]

Blue Angel, thank you for looking into the 19z porsche caliper retrofit and actually doing a detailed comparison of the available upgrade options an comparing both performance aspect as well as a safety side of the matter. I saw your post yesterday so it took me a day to located the G series pads locally and do a few side by side measurements to get the idea (i have very limited experience with G series calipers because it is not a popular upgrade in the f15/e70 crowd). Now i got a little confused with the available options (added tow/brake package etc) but i did got the pads that fit 2021 540i and fit x5 and they are supposed to work with a 374mm disc.

I also Wanted to add a few things on the above mentioned info as well:

1) i am using 550iGT rotors that are two piece but have a wider hub than f01 discs, therefore pad is literally 6mm away from center (1/4” see pic). Also pad is flush with the outer edge of the disc , i dont have picture because I immediately sell out of all my kits , they are in major demand with f15 platform), but believe my word the pad is flush lol

2) very light pad taper is normal with any vehicle and is negligent, any significant taper would only happen if you track hard and literally abuse you vehicle and brake system, highly unlikely with f10/f15 platform, id say this would be negligent in this application in my opinion

3) 10% increase in clamping force in a 4000lb vehicle again is negligent, but bigger pad would add to consistent braking performance. Id always suggest larger rear brakes to avoid possible bias. Again above mentioned situation is somewhat possible in a harsh and severe conditions similar to track use, pad getting hot is normal, and pad/rotor this large is made for this particular purpose lol. A few of my customers tow trailers/boats, a couple live in the mountain area and subject their x5s not only to standard towing but also severe stress on the brakes from descending with a trailer. Also keep in mind f15 weigh a good bit more than f10 plus trailer weight ofcourse.

4) brackets are standard for f85, m5, Porsche, and many other vehicles/models. It is about the only design for aftermarket kits from wilwood, brembo, AP and others. Now i saw some people stacking up washers to center the G caliper. This is where i really cry lol

5) I’ll confirm side by side once i get around an x5 or something similar with a g style caliper. To me porsche caliper visually looks much bigger because it doesn’t have holes and vents in it and doesn’t appear to come off a spaceship/look like a chinese folding knife lol.

6) true, very few 18” wheels would clear 19z caliper , i also seen that G calipers have to be shaved down/spacers used, but it is a part of modding so not big deal

7) 100% i was impressed how wide these pads are. One thing to keep in mind is 6 pistons will offer a very TALL pad , i added pictures of the pad sizing, now with my very rough calculations porsche pad offers about 22-25% more contact area. I got gseries pads from the local parts house, the cheapest brand ran me 150. Pad selection for Porsche is very solid. Much better pricing from what i see as well.

8) if the finish on the G caliper is same as my f85 caliper, then it is pitiful. I attempted a VERY LIGHT polish of the caliper and instantly burnt through the edges. Given i work with very high end vehicle finishes almost daily, and know of clear coat, polish, correction, and had years of bodywork/prep experience as well
There was no way i could burn through it unless paint doesnt have clear (hence m decal coming off of these often as well). My kits are fully sandblasted, prepped, and sprayed in a local auto restoration shop, their finish is 100% spot on, no trash, paint sticks excellent, and hadn’t had an issue with my kits in 2 years yet. I have my upgraded rear calipers on my x5m and looking into respraying my factory fronts by the same shop.

To somewhat sum it up, porsche pads offer larger contact patch vs g series because of 2 more pistons, caliper itself appears larger and more period correct/less futuristic because it doesnt have holes and voids , and i highly doubt the 10% difference in clamping force would be felt by 99% of the owners. Braking would be more noticeably affected by proper choice of tires or pad compound. 550iGT rotors fit close to perfect with a properly machined caliper and leave 6mm ring, same as factory x5m front brake rotor/pad set up. Pad cost from my personal experience is definitely higher with gt caliper (i paid 150 for a none set oooof) lol. Plus like mentioned above, these just look badass 😁
I finally got my first f10 series batch dropped off for paint, should see installed test results/reviews soon hopefully. Again thank you for looking into what i got to offer, hopefully these would stand a chance with this community, definitely let me know what i missed, sorry been driving all day, tried to mock up this post best i could

Originally Posted by Blue Angel

OK, so I looked into these 19Z calipers a little closer. Turns out they have 36mm pistons, all the same size (not staggered like many do). This means they have 10% more clamping force than the G-Series calipers (40/44mm) and E70 X5M (42/42mm), and 16% more clamping force than M5 calipers. This is not a good thing, this is bad as it will lead to a more front-biased brake force distribution (rear brakes will have less braking torque when the fronts lock up). This means longer stopping distances and more wear/heat in the front brakes vs. the rears.

So the disadvantages in using a 19Z caliper on a 5-Series compared to the G-Series calipers are:

1. Narrower pads that don't cover the surface of BMW 374mm rotors (they are commonly sold with brake upgrade kits using 380mm rotors). This can be seen in the assembly pictures posted above, and the outside of the pad may go past the outside of the rotor by a few mm

2. Symmetrical pistons that could lead to tapered pad wear (BMW G-Series calipers use 40/44mm pistons). To be fair, the E70 X5M calipers also use symmetrical 42mm pistons

3. 10%/16% more piston area (clamping force) compared to G-Series/F10 M5 calipers (respectively) which will cause a forward braking bias, increasing stopping distances and adding more heat to the front brakes (reduced rear braking). Add the narrow pad design that's biased more to the outside of the rotor and this situation gets worse

4. Require custom brackets to mount to F10 spindle. May not be an issue, but more parts introduce more points of possible failure, and custom brackets have not been through testing validation. Probably not an issue, but a data point none-the-less

5. Visually will be nearly identical in size to the 374mm version of the G-Series caliper (they both wrap around a similarly sized rotor)

6. G-Series calipers are cut to accept small wheels. The 374mm caliper has been shown to clear some 18" OEM BMW wheels, maybe some aftermarket also. Lots of clearance for 19" wheels

7. G-Series caliper use very wide pads, allowing the use of the small diameter hat version of the 374mm rotor from the F01 760. This adds much more swept area

8. The finish on a custom 19Z caliper may not be as durable as the factory finish on a G-Series caliper if you find an original blue caliper from an MS Brake equipped car. If you're painting yourself it's a tossup

The one advantage I could possibly see on the 19Z caliper is it could potentially have better spoke clearance for wheels. I say potentially only because the G-Series caliper has shown to be tight on some wheels, requiring the use of a spacer. I have no idea if the 19Z is any better or not as I haven't tried one.

For all the reasons I state above, my personal opinion is an F10 owner should try to use one of the proven upgrade routes with BMW calipers if possible before looking to calipers from other brands. Numbers 1-3 above will be issues if you are using 374mm BMW replacement rotors. #3 might not be an issue if you are using an upgraded rear caliper as well, but to know for sure you will have to look at piston diameters, rotor dimensions, pad fit, and pad effective radius to determine whether you are negatively affecting your brake bias or not.

Sorry for sounding so negative dentprotony, but I just want people to know wheat they're getting into should they choose to upgrade.

To anyone thinking of upgrading, please check out this thread where most of your options are thoroughly explored and tested:

https://f10.5post.com/forums/showthread.php?t=1488894

It's a ton of reading, but it will be worth it if you decide to go ahead with an upgrade.

[Blue Angel]

1. My mistake - I should have guessed that a custom made bracket would position the caliper properly with the outer edge of the pad aligned with the outer edge of the rotor. Oops! BUT, if the pad is 6mm from the inside of the wear surface there will be 6mm of exposed brake disk that will rust, unless the disc is factory coated or painted in such a way that the coating wears off with pad contact, no?

2. Very true, and which is why I mentioned the equal sized pistons in the X5M calipers. However, tapered piston sizes are a modern trend for a reason, both on four and six piston calipers, and all else equal would be considered an advantage. Likely not a big deal.

3. I'll come back to this below.

4. Washers can't break, they're in compression. Point taken though, and you are correct that many BBKs use brackets to adapt universal caliper designs to different chassis. As long as your bracket designs have chamfered/radiused edges and corners to eliminate stress risers (crack initiation) and use OEM grade hardware with thread-lock, they are likely fine.

5. Bring a tape measure. There are three sizes of these calipers designed for three different rotor sizes: 348mm, 374mm and 395mm. The smallest ones are very common on new BMWs. Personally I think both calipers look mighty impressive. Bragging rights to the 19Z for being a six piston design, but cosmetically it's 100% subjective

6. 4-5mm spacers and longer bolts are necessary to adapt to the older F chassis, yes, but shaving the caliper is only required for certain wheels with very little spoke clearance. I'm the one who used a router to carve the calipers to fit the 408M wheels, but those wheels are designed for the M5 which has massive 400mm brakes and relatively narrow six piston calipers that are positioned quite far from the center axis. There are plenty of wheels that clear the G-Series calipers without issue. If not there would be a shortage of newer BMWs with aftermarket wheels

7. True, the pads look to offer more area which should spread heat out more. G-Series pad choices are limited, but are improving since these are fairly new to market.

8. I'll give you that one based on your professional experience in paint/finish work. I'm definitely no expert in that arena.

Coming back to #3

If as a vehicle owner you consider a brake upgrade as purely aesthetic and give no thought at all to stopping performance, please stop reading here and put whatever caliper from whatever car onto whatever you're driving and don't give it a second thought.

If you care about stopping performance it would serve you well to understand a little bit of data. Not everyone understands things well enough to calculate all of this, but most people should be able to understand it once it's laid out. The table in this post assumes equal line pressures front and rear (no ABS engagement) and equal brake pad friction coefficient:

https://f10.5post.com/forums/showpos...&postcount=435

What you need to know is the M5 is the most aggressive (read: rear-biased) brake system BMW released on the F10 chassis. Cars are designed to understeer (lose traction on the front axle) to keep the back end from sliding during cornering and braking maneuvers. The M5 has 37.1% rear brake bias, where all the regular versions have between 34.8% to 35.3%.

For example, adding this 19Z caliper/rotor package to an F10 535 would decrease maximum braking deceleration by close to 5% (the rear brake bias would drop from 34.3% to 31.4%). This is because the car is already limited by the grip of its front tires, so shifting more braking torque to the front axle just limits the amount of braking the rear wheels can do. If you'd like me to share the math on this I can, it's pretty much just calculating how the 19Z caliper/rotor swap fits into that table and then correcting for reduced line pressure to the rear brakes.

As I said before, if a rear caliper upgrade was done at the same time and was calculated to work properly with the front brakes, or a brake proportioning valve was installed, or if experimentation and testing was done with higher friction rear brake pads, or if a loss of braking performance is not a concern, then I see no issue with this modification.

[Blue Angel]

Originally Posted by Blue Angel

As I said before, if a rear caliper upgrade was done at the same time and was calculated to work properly with the front brakes, or a brake proportioning valve was installed, or if experimentation and testing was done with higher friction rear brake pads, or if a loss of braking performance is not a concern, then I see no issue with this modification.

In case my post is coming off just too negative...

What are the specs of the matching rear caliper you show in your images? Perhaps tooling up a bracket to fit that to an F10 would make for a compelling upgrade? We all know the pathetic looking single piston sliding caliper on the back of ALL F10's is just way out of place on these cars.

If you can give me the piston specs and pad dimensions I'll put them in my spreadsheet and see what they look like as a system.

[Unspec]

To chime in, since I also had to knock the edge of my caliper to make it fit better with 343M wheels: it's likely a relatively obscure issue due to the 5x120 wheel pattern on our cars vs the 5x112 pattern on G series cars that allow them to run slightly smaller wheel "centers" (hubs? idk). The 6 piston style ones are far less "blocky" than the G series ones, which is why they usually fit with minimal wheel clearance issues so long as the barrels themselves fit over the calipers.

[Blue Angel]

Good point. For a given working surface area, yes, six small pistons tend to lead to a narrower calliper/pad assembly and perhaps more tolerance of tapered wheel spoke profiles than a system designed around four larger pistons.

However as you and I have both discovered first hand, that doesn’t mean the four piston system can’t work with such wheels. In the case of modern BMWs having gone to a smaller hub and 5x112 bolt pattern, the resulting clearance allows for a bulkier calliper. Perhaps a stiffer calliper too? Quite possible.

Porsche also uses an incredibly large 5x130 bolt pattern, which drives larger hub sizes and puts more physical constraints on brake system design for a given wheel size.

Thinking this through… it seems moving to the smaller 5x112 bolt pattern makes for smaller lighter hub components and increases clearance for brake calipers, which in turn makes larger (and potentially stiffer) 4 piston designs easier to implement. 4 piston calipers are cheaper to manufacture than 6 piston designs as well.

Weight savings, decreased fuel consumption and cost savings all in one strategic move, and all they had to do was copy the competition (lol). Seems smart to me as long as they can keep the rigidity of the hub/bearing assembly where it needs to be.