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

fmorelli

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Curious the weight difference...
Me too, since I happen to have both here new. Did rears as well and will have photos of that installation this week. About a 10% weight savings on the 2-piece aluminum rotor.

Rear Z4 35i rotors are little baby things lol. These were rusty (junkyard) but like 5k use, so like new.

Filippo


F30 S2HNA Front 370mm BMW p/n 34106797603
1-piece rotor (Zimmermann p/n 150290532)

IMG_20200712_090810.jpg
F30 S2HNA Front 370mm BMW p/n 34106797603
1-piece rotor (Zimmermann p/n 150290532)

IMG_20200712_091228.jpg





BMW E89 Z4 35i Stock Rear Rotor 300x20mm
BMW p/n 34216782605


IMG_20200712_091334.jpg

BMW E46 M3/ E86 Z4 CSL Front Rotor 345x28mm
BMW p/n 34112282445

(application - E89 Z4 rear big brake conversion)​

IMG_20200712_091304.jpg
 
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billj457

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Great thread! If you happen to still have your stock 325M wheels, do they fit in front with the 370mm setup?
 

Torgus

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Newb question but do they not make a 'real' BBK for the z4 like from brembro, stoptech, etc? I know it is less expensive piecing kits together don't get me wrong.

One thing I have always wondered when adding calipers not designed for the car is how do you keep the brake bias and ABS functioning 100% like it is supposed to? Once you change the number/size of the pistons in the calipers and or brake master cylinder from stock doesn't it throw everything off? Unless you have a stand alone ABS controller: http://info.3dmmotorsport.com/mk60-motorsport-abs-standalone-guide

https://www.brakes-shop.com/brakepedia/bbk/abs-and-brake-kit-fundamentals <-- A good read, a bit technical

"at STOPTECH all brake upgrade kits are designed with the characteristics of the original braking system taken into account to minimize these differences. This is the reason that when you order a STOPTECH big rotor upgrade kit the new caliper bores may actually be smaller than the units you are replacing to "balance the equation." This is just one way in which our engineers attempt to retain the original system's P-T and P-V integrity. Sure, it's not one-size-fits-all, but neither is your car…or your driving style. Why should you expect any less from your brake upgrade?"
 
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fmorelli

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We worked much of today. Slow but steady progress. Ran into a few issues but no show stoppers. The G30 M-sport calipers are a millimeter shy on clamp width, so need to mill off 30 thou off each rear brake pad. I swapped the rear actuators from G30 to E89 - connectors are different. Fitting is tricky, getting clearance for how this is mounted, so the rear EMF clears both the chassis and the external controls on the TTX. Further tomfoolery is that the G30 calipers are actually front mounted (9 o'clock) on the G30, but we need them mounted at 3 o'clock. So we swap calipers left to right so we get the bleeders upright. Thankfully the EMF controllers are designed to clear mounted either up or down.

Devil is in the details ... all the research, mockup etc ... but reality is an unforgiving teacher and, sometimes, we get lucky.

@Torgus yeah only company on the planet that makes an EMF-based BBK is PB Brakes. Works great. Not cheap. In my case I wanted a factory look for a few reasons where I won't digress here.

Filippo

E89 Z4 TTX : CSL.jpg
 
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fmorelli

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Alright a few more photos. We've been working fitment in the rear. This is all custom in a way that's not been done before, and bench mock up only gets so far. We missed one or two small things along the way, but we have addressed them. One of the Torx bolts I used required knocking 2mm off the ends, for clearance. Bracketry is tight, with backspacing from the EMF actuator to the Öhlins TTX lower shock body, but we believe we've got reasonable spacing now. One thing I completely missed - and I had to go back and look at photos to verify I spaced - I never tested caliper width relative to the new rear rotor setup (versus the Gen 1 F30 rear rotor). Turns out pads don't quite fit with the massive 28mm rear rotor thickness. We knocked a few mm off the pads with the mill, and all is happy. This setup is massive for the rear of the car, so no real concerns as a ton of pad is still there.

Clearance on lines and plugs are good. Amazing given we're running G30 m-sport calipers backwards with side-to-side swapped. I was able to swap the G30 actuators (different plug config vs the E89). The E89 actuators bolt right up to the G30 rear caliper. A lot of shenanigans to sort all of this out, especially when we'd found no information from anyone prior attempting any of this.

Next we'll hook up caliper lines, bleed the whole system, validate that the EMF is happy, bed this setup in and see if we have a proper working brake system.

Filippo

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fmorelli

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With two initial test drives, I can attest that this system is functioning. Initial EMF-related codes cleared from changing everything out. Parking brake works great and the brakes are generally operable. I did an initial pressure bleed, but still have some air bubbles so a bleed with ISTA will take care of that.

Filippo
 

fmorelli

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Sooo I missed a small detail which I'm addressing now. The rear rotors are hubcentric, like the wheels. The rear hub is stepped. The OD for the rotor is 75mm, then steps down to 72.6mm for the wheel. The E46 M3 CSL front rotors I am using in the rear have an 79mm ID. While I can center everything, hold it in place with the rotor nut, then lock it in a wheel sandwich ... yeah ... sketch. So I'm milling a 75mm ID x 79mm OD x 6mm aluminum 6061 rings so the rotors sit properly centered.
 

Krampus

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Really nice work 👍. Maybe some day i'll upgrade my Euro brakes.
Small detail about 35i stock brakes. US vs Euro models. US front 330mm*24mm and rear 300mm*20mm. Euro front 348mm*30mm and rear 324*20mm.
US and Euro 35is brakes are the same. Front 348mm*30mm and rear 324*20mm. Correct me if I'm wrong.
 
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fmorelli

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Thanks. The front is standard E8x/E9x upgrade to F30 msport / F8x type brakes. Really straightforward. I would not recommend my rear upgrade to anyone - practically speaking, just spend the money to buy one of the rear upgrades from the aftermarket (PB and others). I only went this route because I wanted the brakes to look "stock". SIlly I know ... but I have my reasons ;-).
 

fmorelli

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Well ... and I thought I was done. Not sure how I missed this but the E46 M3 CSL front brake rotors, which I am using on the rear of the E89 Z4, have a slightly larger hub center. Sooooooo ... had to machine up some spacers - 75mm ID x 79mm OD x 6mm with a back cut to clear the center-to-face radius on the hub. (yes I made a spare set)

PXL_20210715_144756247.jpg PXL_20210715_215755783.jpg PXL_20210715_215830456.jpg

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fmorelli

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Thanks. For the record, I would not advise this approach for the rear of the Z4, to anyone else. PB Brakes or equivalent, all the way. Buy once. Cry once. lol
 
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fmorelli

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So how does the braking feel?
Still not happy with it. Mid-soft pedal feel on first push, hard on second. I did a power bleed twice. I've done one manual bleed. ISTA vibrate on all. I'm going to do another manual bleed (person pressing pedal).

I've heard from a number of people running bigger brakes setups that the stock booster works fine. So I don't think it is a booster size issue (and Z4 booster is unique ... at least I've not found a swap). I think this is a pesky Ex bleed issue.

When I did my X5 big brake upgrade, had issues bleeding that too. Power bleed is just a non starter on a brake caliper change. But I digress.
 
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