E89 Z4 4-corner big brake upgrade with Brembo m-sport calipers

[fmorelli]

In mid-2019 @barry@3DM and I began discussing rear suspension upgrades for the Z4 to prepare for a circa 600whp drivetrain. What started in the rear blossomed to a complete bespoke suspension which changes out quite a variety of components. Along the way I realized that some of these changes created a potential opportunity to further upgrade brakes, which also went well with the power upgrades. I wanted a factory-like solution, and began doing research in December 2019. The Z4 is particularly difficult to upgrade in the rear due to the factory EMF braking (electronic rear brake integrated with rear caliper).

Working with Barry, I have now gotten far enough along that I can start sharing the results. I want to thank @barry@3DM at 3dmmotorsport.com, as his facilities and expertise were invaluable to my working out this brake system.

Front: 370mm Brembo M-sport calipers and 2-piece rotors
Rear: 345mm factory brakes with EMF and 2-piece rotors

I would hazard a guess that I have about 100 hours or research and development time into this. In this thread I'll share info which I hope is useful both the Z4 people, and those with EMF systems (later model cars) that are looking to upgrade rear brakes.

Here's a outline of the thread. I'll tack post links for each as this gets filled out:

1. FRONT BRAKES AND ROTORS (Post #2)
2. REAR CALIPERS AND ROTORS (Post #4)
3. MATCHING UP REAR CALIPER EMF - A BRIEF GUIDE (Post #6)
4. REAR CALIPER BRACKET MODIFICATIONS (Post #16)
5. DESIGNING REAR CALIPER BRACKET ADAPTERS (Post #17)
6. PREPPING TRAILING ARMS FOR NEW BRAKES (Post #19)
7. BESPOKE CALIPER BRACKET ADAPTERS (Post #25)
8. FRONT ASSEMBLY (Post #31)
9. REAR ASSEMBLY (Post #44)

Filippo

 

[fmorelli]

FRONT BRAKES AND ROTORS

Let me start on the easy side - the front brakes, as that is most straightforward. The E89 Z4 effectively shares the same front suspension and hub assembly components as the E90. To refresh, the front is largely E90 (minus a few small variations) and the rear is E46-derived which by that I mean there are some evolutionary updates specific to the E89 Z4. On the fronts, you can search forums on E90 big brake upgrades. We have such a discussion here on Spoolstreet.

So with the fronts in my case, we are running the F30 m-sport option brembos. I'll provide a little info as a roll-up, which digging through threads you would also find:

• F8x/F3x m-sport 4-pot Brembo brakes came in blue from BMW AG (34116799469 and 34116799470). Some cars received red or yellow versions installed at port or by dealer. Specifically the cars were VO coded S2NHA.
• All Brembo calipers have a stamping on the rear that indicate intended rotor size. These calipers have 370/380 stamped on them. The F3x run a 370mm rotor while the F8x run 380mm rotor, both using this same caliper.

In my case we are swapping out my hub carrier to F3x, which will accept the E89 Z4 hub bearing. Note the F3x hub carrier changes the strut clamping diameter (which is what originally drove us to F3x given a new suspension design). So one cannot swap this hub carrier straight into a Z4 without addressing strut clamping diameter. The F8x hub carrier is very similar to the F3x, but with some added differences around reinforcement webbing and bump steer which is well outside the subject of this thread. BUT IN SUMMARY, if you want to run the big Brembos on your E90-based hub carriers, go hit the thread I posted above for information on that.

With that said, front rotors in my application are 2-piece aluminum/steel 370mm x 30mm slotted, dimpled and non-directional. One can run the factory BMW F3x m-sport rotor (BMW p/n 34106797603) or Zimmerman makes an excellent version of this 2-piece rotor (150.2905.32). I worked with the FCP Euro BMW catalog manager to get them to stock this rotor, as it is not highly available in the USA but commonly used in Europe.

On finding front brakes - mostly eBay is your friend. Be aware that almost any brake you get will have damaged powder coating. I suggest getting Estoril Blue Metallic II (code B45) touchup paint - it's about as close as one can get to the powder coat color.

A quick note about the brake booster. I have other friends running the big brake setup and they have found no reason to deviate from the stock brake booster. in the case of the Z4 this is particularly good because the brake booster is unique so upgrading to say the e92 M3 brake booster is out of the question.

I'll provide a few photos of the calipers and hub carrier.

Filippo

 

[Seb335i]

I'm looking forward to see final rear setup.

 

[fmorelli]

REAR CALIPERS AND ROTORS:

Alright let's get to the trickier part of the Z4 brake upgrade. The E89 Z4 was the first model to carry TRW's new integrated electronic rear brake. The includes a switch-operated rear brake. On manual cars, logic also exists to hold the brake for a brief period when started from a stop on inclines. The EMF system consists of two components - the EMF actuator, integrated to the back of the rear caliper. I'll go into this more in the next post. The issue, when changing brakes, is that standard rear calipers have no EMF integration capability. Line locks and other solutions are not substitutes. The only aftermarket rear brake solution for EMF-based cars (including for the E89 Z4) is made by the Taiwanese firm, PB Brakes. @jts1981 can attest to the quality of their brake package.

The Z4 35i runs a 300x20mm rear rotor. The Z435is increases the assembly to 324x20mm. I was looking for a 345mm rear rotor and caliper combination that I could retrofit.

I basically cataloged all BMWs that have rear EMF brakes. In 345mm, caliper and rotor assembles exist in these models
Group (A): F10 550i-x / F06 F11 F12 F13 640/650
Group (B): F06 640 / 650 M-sport
Group (C): G30 530e/i/iX 540i/iX/dX / M550iX / G11 750iX / G12 740i/iX 750i/iX

Group (A) and Group (B) share the same rotor 345x24mm (p/n 34216775289). Basically the rear caliper and brackets are the same across both Group A & B, though B is powder coated black.

Group (C): when coupled with the S2NHA (m-sport) package, has rear caliper (p/n 34216881295) and brackets (p/n 34206891915) powder coated in blue, which match the S2NHA 370mm brembo front calipers from the F30. That's what I ended up going after. Problem is that package is exceptionally rare in the USA.

Lo and behold I was talking wtih my good friend Sebastian (@Seb335i) who has a BMW shop in Paris, and he tells me he has a set of G30 m-sport rear calipers and brackets on the shelf. I thought he was kidding me. I said, "they are blue?" He said, "yes." I could not believe it - I had spent at least a month researching brakes, finally deciding on this rear combo, then hunting all over the USA, talking to dismantlers, and even searching in the UK. Sure enough he sent me a photo on his bench.

@Seb335i had acquired these for a customer's car, which turned out needed something different. Packaged and shipped - these are The French Connection brakes for this setup thanks to Sebastian.

Now the rotors are a different animal. I spent a tremendous amount of time on the Zimmerman catalog crossing various rotor sizes. Initially I went with F30 rear rotors but we could not get the backspacing sorted out. I'll forego the many photos of doing the mockup of those and move to the final choice for rear rotor. But first a quick photo to show the stock 35i rear rotor versus a 345mm rear F30 rotor.

We had backspacing issues with the F30 so it was back to the drawing board. After many hours of pouring over brake specs, I found that the FRONT E46 M3 CSL Competition (VO S7MAA) 2-piece rotors (p/n 34112282445 and 34112282446 - they are directional!) were in the zip code of specs for the setup I wanted to achieve. The only issue was a slightly thicker rotor at 28mm versus the 24mm used on the rear BMW caliper assemblies I had cataloged. But this we could over come. Thanks to FCPEuro for the photo and shipping the rotor .

So with the G30 S2NHA rear calipers and E46 M3 Competition front rotors, we began working all the mockups at 3DM Motorsport. I'll cover all of that in a follow-up post.

Filippo

 

[fmorelli]

A few photos of the calipers after they were cleaned, and touched up with Estoril II touch-up paint. Everything cleans up very well. With a coat of wax, like new.

Filippo

 

[fmorelli]

MATCHING UP REAR CALIPER EMF - A BRIEF GUIDE:

Before we get to working through fitting the rear calipers and rotors, let's run through some details on the BMW EMF system which is designed by TRW. The E89 was the first BMW chassis to employ electromechanical parking brake, which is known as the EMF system. It performs several function, not just actuation by an electrical switch in the cockpit. ABS integrates for emergency braking function, and manual cars have logic for holding brake momentarily when starting from a stop on inclines. If you'd like to understand a bit more about the EMF system, this high-level EMF guide from TRW is useful.

First generation EMFs (which have a variety of dot releases, lets call them in software-speak) have 3 dedicated components - the EMF button in the cockpit, the EMF control unit which is a black box mounted to the rear of the car for each brake caliper, and finally the EMF actuator which is an electromechanical device integrated into the back of the rear caliper which compresses brake fluid upon actuation. This system is further integrated with DSC, but that is not relevant to our quest. (if you wish to understand EMF in more detail, which is not necessary for this discussion, look at section 3.2 Brakes in the E89 Chassis and Suspension BMW technical training document).

To figure out this upgrade, I began working through the BMW product catalog to determine what later chassis' have employed EMF. Crossing part numbers I made a small discovery - that later cars upgraded the EMF control unit but maintained the same EMF actuator (BMW p/n 34216794618) on the rear calipers as the E89 Z4. This told me that I could use later model rear caliper assemblies and my EMF control unit would not know the difference. Whether the EMF controller can be upgraded was not relevant to upgrading the caliper and rotor size at the rear. Note digging in to the models below start to reveal possible rear brake assemblies, which also vary by VO option codes.



As I noted in post above:

I basically cataloged all BMWs that have rear EMF brakes. In 345mm, caliper and rotor assembles exist in these models
Group (A): F10 550i-x / F06 F11 F12 F13 640/650
Group (B): F06 640 / 650 M-sport
Group (C): G30 530e/i/iX 540i/iX/dX / M550iX / G11 750iX / G12 740i/iX 750i/iX

In later versions of the EMF system, found for example in the G30, the EMF control unit is no longer a standalone module. The EMF logic is integrated into the DSC module. Nonetheless the G30 continues to use the same EMF actuator on its rear caliper assemblies.

Filippo

 

[Lurcher]

Take any weights on the different systems? I know the BMW performance brakes I put on the front seem substantially heavier (like ~5+ lbs per corner) than stock.

 

[fmorelli]

Take any weights on the different systems? I know the BMW performance brakes I put on the front seem substantially heavier (like ~5+ lbs per corner) than stock.

No haven't done so. yes I expect it to be heavier as you noted.

Filippo

 

[Eracer76]

I also spent many hours looking for rear rotors with similar offset specs as the Z4 rotors, and came up with the same E46 M3 competition rotors as you

 

[fmorelli]

I also spent many hours looking for rear rotors with similar offset specs as the Z4 rotors, and came up with the same E46 M3 competition rotors as you

Assume you ditched EMF. Did you do any coding to support that? If so curious what you did. If not any side effects not having anything connected to the EMF controller?

Funny ... E46 M3 competition rotors are not exactly the first place one goes looking for rotor fit. Hilarious we both ended up there!

Filippo

 

[aus335iguy]

Great thread @fmorelli. Its about time someone showed the Zs some retrofit brake love!

 

[doublespaces]

In later versions of the EMF system, found for example in the G30, the EMF control unit is no longer a standalone module. The EMF logic is integrated into the DSC module. Nonetheless the G30 continues to use the same EMF actuator on its rear caliper assemblies.

So, I'm trying to understand here, this part isolation gave you reason to believe you could use the G30 actuator with your Z?

 

[fmorelli]

So, I'm trying to understand here, this part isolation gave you reason to believe you could use the G30 actuator with your Z?

I may have buried the info. BMW p/n 34216794618 is the EMF actuator on the E89 Z4 rear caliper. Turns out any number of BMW EMF rear calipers use that actuator attached to different brake calipers. They also use different EMF controllers to actuate the same EMF actuator.

So basically ... as long as the rear caliper has that actuator (regardless of which controller is in the chassis), I'm pretty certain it will work on the Z4. Hope that helps.

The reason I chose the G30 rear caliper (which runs the same actuator as Z4) is that the m-sport version comes in 345mm calipers powder coated in blue which match the front blue F30 m-sport brakes.I can be a bit picky on looks I suppose. There are other rear calipers that are up to the upgrade task.

Hope this clarifies.

Filippo

 

[doublespaces]

Ok, so this 'confirms' rotor flexibility, in this case it's the rotor/actuator combo, I believe I follow

So the next step is to mount the parts and test them with the car?

 

[fmorelli]

Ok, so this 'confirms' rotor flexibility, in this case it's the rotor/actuator combo, I believe I follow

Sort of yes. But rotor is a separate fitting. Rotor has four fitment criteria - 1) hub center (common), 2) close diameter match, 3) close rotor thickness match, 4) rotor hat to rotor face distance (how deep is the hat).

I initially tried F30 S2HNA rotors. They were too deep and I could not get it to work. I mostly have not spoken about what didn't wok on the thread, in hopes to cull some posting and confusion.

You might ask, "why didn't you take all known measurements and figure that out ahead of time?" That would be a really great question (yes I'm leading the questioner ). I did do that - I took all known measurements and started working the subset of possible answers. But those measurements that come from rotor, bracket caliper, hub, and mounting tabs. Mounting location can also effect this. And then the fitment is quite close (which you'll see in upcoming posts where I show the physical fitment process. So measurements get one close but not close enough - physical mock-up is required. Without jumping ahead, I'll say the F30 m-sport rear rotor hats were too deep and caused contact with the trailing arm tabs and caliper bracket. It's not visible in the photo, but this is just a snap of the mock-up process with spare trailing arm on the bench.

Doing mock-up with like-new powder coated parts was a PITA. Easy to marr stuff on the bench with all the steel around and all the movement.

So the next step is to mount the parts and test them with the car?

lol ... well ... yes ... from first post

1. RONT BRAKES AND ROTORS
2. REAR CALIPERS AND ROTORS
3. MATCHING UP REAR CALIPER EMF - A BRIEF GUIDE
4. REAR CALIPER MODIFICATIONS
5. DESIGNING REAR CALIPER BRACKET ADAPTERS
6. PREPPING TRAILING ARMS FOR NEW BRAKES
7. BESPOKE CALIPER BRACKET ADAPTERS
8. FINAL ASSEMBLY

I've posted #'s 1-3 at this point. Physically, @barry@3DM and I are actually at #6. We know it all fits. I didn't want to start this thread until we'd done the physical work. So that said the fun part of the process - #'s 4-6, is coming as I get to typing and culling from too many photos in my build repository.

Filippo

 

[fmorelli]

REAR CALIPER BRACKET MODIFICATIONS:

Okay ... let's get to some of the more fun stuff. I realize the first several posts were legwork.

ONE THING TO NOTE - the G30 rear caliper is front mounted on the hub - so it's position is circa 9 o'clock when facing the hub. Since the E89 is oriented at 3 o'clock we are actually going to mount the rear calipers reversed - left side on right and so on. This positions the brake bleeders correctly.

So with the 28mm rear rotor, there is some clearance work that needs to be performed, to the caliper brackets. There is basically 27.7mm of clearance on the bracket.

To machine the bracket, we needed to make a fairly stiff tower to which the bracket could be mounted, then affixed to the mill base.



The area of interference is not part of the bracket's frame structure, but rather the rail blocks on which the brake pads slide. Removing some material from this area does not effect the strength of the bracket. The corresponding stainless clips need to be shortened slightly as well, which was done with a Dremel tool. While not shown in the picture below, the stainless steel tab on the rail which protrudes slightly was bent flat with a needle nose to provide additional clearance.

Once milled there is enough space to mount the caliper with rotor. I fabricated aluminum spacers to center the caliper bracket on the rotor. This is all a process to ultimately be able to establish a location for the caliper bracket mounting relative to the two mounting tabs on the trailing arm assembly.



With appropriate clearances, we are able to locate the caliper bracket relative to the tabs. This gives us runway for working on the caliper bracket mounting location, and designing the mounting brackets.

Filippo

 

[fmorelli]

DESIGNING REAR CALIPER BRACKET ADAPTERS:

With the caliper brackets fitting over the rotors, we're able to start getting measurement and fitment for the caliper bracket adapter. The fit between the mounting tabs and rear caliper bracket is very close. This was the original issue with the F30 rear rotor mock-up, and eventually got us to the E46 M3 Competition front rotor for this application.

Given my profession, I work with wood, it's the perfect medium to easily create and iterate a caliper attachment. First off I created four aluminum shims, which center the caliper bracket on the rotor (the shims fit between the rotor and caliper brake pad slide area). The pads help locate the caliper bracket relative to the rotor; clamps lock them together. One can see how close the bracket is to the tab. We want as little of a moment arm from the adapter bracket, so we aim to minimize the offset of the mount points from the tabs to the mounting holes.

A few things to consider in the task of determining the bracket dimensions. I am going to start out in wood, since it is easily workable. But ultimately the wood buck helps arrive to a set of drawings which make their way to CAD so the result can be fabricated from mild steel. With that said, I started with a spanish cedar wood plate which is hardwood but marks easily. The plate was relieved so that it fits the caliper mounting tabs; it is then clamped to the tabs, with an outline of the tabs taken with a pencil, and center point marked for the tab hole.

The trickier part is locating where the caliper bracket holes would like up on the wood adapter plate. I can't remove the rotor to gain access. For this I fashioned a maple dowel pointer, turned to fit the diameter of the bracket hole, and hardened the point. It was short enough to fit between the rotor and bracket, then leveraged with a screwdriver to press an indent into the wooden plate.

With the mock-up close enough, I could take measurements and get an initial drawing together.

 

[NoQuarter]

Love the dowel solution to such a simple task in such a large problem to solve.

Some of my woodworking projects result in good side quests to stop, build a jig, complete original impossible task in seconds.

 

[fmorelli]

PREPPING TRAILING ARMS FOR NEW BRAKES:

These days I just buy junk yard parts and build them up, then swap parts of the Z4. It's really pretty cheap to do and a lot easier to build on the bench. So junkyard trailing arms from two low mileage Z4's were completely stripped, epoxy painted, and fit with Lemforder ball joints and solid RTAB ball joints, plastic hangers replaced per the usual OCD.

I'm posting this a bit backwards, but prior to rebuilding the trailing arms, we had to address how the eventual caliper bracket adapter would mount. With the new bracket, mounting has to be performed from the rear since there is no space to have a bolt head in front of the trailing arm tabs - this is because the caliper brackets cross the front of the tab. To do this I decided to do Helicoil M12x1.5 inserts in the tabs. The bracket will then mount with M12 torx fasteners.

With the trailing arms ready, we move to getting the actual brackets done.

Filippo

 

[Lurcher]

This is like waiting a year for a book, and then waiting for each chapter to be published daily. @doublespaces loving the pageviews!

popcorn in hand!