Its a rear big brake kit Jim, but not as you know it!

[B21]

The subject is BMW Z4 E89 rear brake upgrades.

The key point is that the E89 was one of the first BMWs to use the TRW integrated electrically operated parking brake which is part of what otherwise is an unremarkable sliding pin single piston rear caliper.

Because of this, its very difficult to find carry over solutions from other cars, like the E90s that carried on using a conventional handbrake.

One option for non 35is owners and for non-european 35i owners is to swap the basic 300mm x 20mm vented disc and caliper for a 324mm x 20mm 35is disc and its caliper. Pad size remains the same.

The only aftermarket rear brake solutions for EMF-based cars (including for the E89 Z4) is made by the Taiwanese firm, PB Brakes and Hong Kong based Ceika..typically at around £2,400 for a 348 mm disc..

From my view the style of their calipers is a bit gauche and really you'd need the front and rears to match which pushes it into a £5k-£6k solution.

There was one well documented US attempt at this by using later G series calipers, its fair to say it turned into an engineering nightmare requiring for example hand cut brake pads to make it work!

There were several cars that used broadly the same system and used 324mm or bigger discs.

The actual emf motor part is common to all these, so although some later cars use a different EMF ECU the motor is still the same..so it should work.

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 345mm x 24mm (p/n 34216775289). Basically the rear caliper and brackets are the same across both Group A & B, though B is powder coated black.

TRW.jpg (64.32 KiB) Viewed 1116 times

Group (C): when coupled with the S2NHA (m-sport) package, has rear caliper (p/n 34216881295) and brackets (p/n 34206891915).

The US attempt was based on Group C calipers and turned into an engineering Vietnam!

However, on another forum I saw a Lithuanian had used a Group A/B caliper together with a different 345mn x 24mm disc from a F 5 series BMW with a different offset and some home made brackets.

The details were scant and the OP now long gone.

I've decided to resurrect this and have a go myself.

So Autodoc have my order now..

Carrier, brake caliper
£59.60
Article №: BDA1027 incl. 20% VAT
Quantity : 1
£59.60

Brake caliper
£125.52
Article №: BHS1190E incl. 20% VAT
Quantity : 1
£125.52

Brake caliper
£110.82
Article №: BHS1191E incl. 20% VAT
Quantity : 1
£110.82

Brake pad set
£56.24
Article №: 2470301 incl. 20% VAT
Quantity : 1
£56.24

Brake disc
£106.55
Article №: 150.3461.52 incl. 20% VAT
Quantity : 2
£213.10

Order total: £629

Brake caliper and caliper carrier are TRW and the discs are Zimmerman coated and drilled. Pads are Textar. One caliper carrier is missing so I've bought a 3rd party one and hope it works out OK.

[RobbiZ4]

Excellent!

Hope it's okay for you, if I add two links into the very interesting story from @FMorelli (from an engineers perspective) on spoolstreet.com...
https://www.spoolstreet.com/threads/z4- ... pers.6340/

... as well as into the German ZRoadster forum, where we do have a summary as well for different E89 brake solutions:
DE: a well formatted version in German
https://www.zroadster.com/forum/threads ... st-3705593
EN: translated by Google, but shaked a bit too heavy
https://www-zroadster-com.translate.goo ... st-3705593

[B21]

Excellent!

Hope it's okay for you, if I add two links into the very interesting story from @FMorelli (from an engineers perspective) on spoolstreet.com...
https://www.spoolstreet.com/threads/z4- ... pers.6340/

... as well as into the German ZRoadster forum, where we do have a summary as well for different E89 brake solutions:
DE: a well formatted version in German
https://www.zroadster.com/forum/threads ... st-3705593
EN: translated by Google, but shaked a bit too heavy
https://www-zroadster-com.translate.goo ... st-3705593

Hi Robbi..yes I discussed his 'experiment' with the G series caliper and a front E46M disc combo..his strong advice, repeated often, was don't do what he did on the rears!!!

[B21]

So most of the parts arrived for the ‘small’ BBK for the rear..

F10 series calipers and E60 series disks…these rears are bigger than my current 6 pot Brembo front disks..

Done a first paper mock up of a possible bracket to join these to the E89 chassis.

Not only is the disk much bigger 345 vs 300 or 324 for non 35is / 35is but the depth of the swept area is bigger..pic shows an E89 rear pad (same pad on both 300mm and 324mm rear discs) vs the E60 pad..

Autodoc do a cute trick with TRW ..they sell a ‘remanufactured’ real caliper for about a 1/5 of the price of an E89 caliper..

One caliper bracket wasn’t available in TRW OE supplier so bought a pattern part..interesting to see the myriad of differences…hopefully it will work ok..

[B21]

I've spent some time looking at options above a 345 mm rear disc..

It is feasable (now I'vve climbed a learning curve) to look at other BMW rear calipers with EPB ..

So above 345mm you can go to 370 or 380 or just under 400 with the M5 and M8 rear calipers..

But...

Given the normal front rear bias, what would a similar size rear to front do?

I can see on a M5 fully loaded with pax and luggage why a much bigger rear brake is useful..

With a relatively light E89 not sure.

The other issue is that the price jump on a solution goes from around £500 to over £1,500 assuming using some used parts and over £2k with new parts.

I tried to see if you could use the smaller 5 series caliper with the bigger rear discs but the rear pad does not fully sweep the disc..so that's a no go..

So I'll carry on only withy the 345mm disc upgrade with normal 5 series calipers..

[B21]

So reflecting on the various issues I bit the bullet and bought a couple of old rear hubs and bits with a view to being a lot easy to faff around with bits off the car rather than on..

A few head scratching hours playing with the old bits and my new bits…plus lots of washers, spacers, bolts..

As Meatloaf would say 2 out 3 ain’t bad..however in this case you need all 3 things to work for it to be a viable solution..

These parts are for a 345 mm disc with a 44mm piston sliding caliper solution..roughly based on a 5 series non M

I’ve got a set of M5 rear calipers coming with the option of a 370mm or 380mm rear disc….

New disc is 345mm vs an old E89 300mm disc from the non 35i/35is E89s…

[B21]

First trial fit of the 345mm E60 discs with F series 5 caliper and my first attempt at a bracket ..looks pretty ok..

[RobbiZ4]

FYI:
I found another solution on the ZRoadster forum.

Translated by Google:
https://www-zroadster-com.translate.goo ... r_pto=wapp

Native:
https://www.zroadster.com/forum/threads ... st-3505156


AFAIK not allowd in Germany.

[B21]

FYI:
I found another solution on the ZRoadster forum.

Translated by Google:
https://www-zroadster-com.translate.goo ... r_pto=wapp

Native:
https://www.zroadster.com/forum/threads ... st-3505156


AFAIK not allowd in Germany.

Hi Robbie yup there are two HK/Taiwan guys …problem is there 345mm solution is £2k plus vat and duty ie £2,500..mine is around £650..inc taxes

And cosmetically you really need to but their front set to match ..

[B21]

My M5 calipers arrived today…messed around with them and quite quicky, with the steep learning curve I’ve been on about disc/pad/caliper design have decided it’s a bridge too far…it’s only going to work with its own 380mm disc which are £300+ each…so they’ll be going back on eBay…

Strangely the pads look the same so great change in caliper / pad performance just a bigger expensive disk..

[B21]

As I tried to use a 4.5" angle grinder to take my left index finger off I thought I'd wash the blood off the old stock E89 rear brake pads..

So here you are..

Top row..left to right

Stock E89 non N54 pad for 300mm x 20 rear disc 42mm piston (US market 35i)
Stock E89 N54 pad for 324mm x 20 rear disc 42mm piston
Stock F 5 series pad for B21 345mm x 24 rear disc and hopefully 370mm x 24 rear disc 44mm piston



Bottom row left to right

Front pads

Stock M Sport pad as used in 340mm 370mm and 380mm x 30mm F and M2 M4 series front dual piston calipers 2x 44mm piston
Pad for upcoming front BBK Brembo 6 pot for use with 380mm x 30 mm F series M2 M4

[B21]

The F01 7 series rear discs arrived..

Found a UK company selling high carbon content drilled discs to match my 380mm M2 M4 fronts..

So it turns out for the 370 rear disc two options exist..

Either you can use my 345mm caliper carrier bracket adapter with a F series M5 caliper carrier OR…await the second 370mm specfic bracket ..that uses the F series 5 550i carrier bracket…

In both cases the caliper bracket needs machining..not that the required machining is difficult to be done at home.

The rear caliper in all cases is the F series 5 550i caliper..

I’ll fit the 370mm rears to match my 380 M2/M4 discs mated to the Ford Mustang GT350 Brembo 6 pot calipers…this will keep the front / rear brake ratios in the correct area..

Price for 345mm or 370mm discs are around £150 for a pair…caliper carriers are around £50 ish and calipers can be had for £50.these are all new prices..so a rear brake kit kit for £350 plus the price of my brackets..

Pics show stock rear Z4 300mm disc and 345 mm and 370mm disc options..

[B21]

Played around with my rear BBK upgrade today…

Discovered F version 5 series rear calipers are made of alloy not cast iron as on the E89..this E89 caliper carries its 300mm stamp indicating it’s for 300mm rear discs only..

Also the M5 caliper looks to be just a 5 series caliper painted blue..albeit with a taller caliper carrier cradle…not a lot of people know that..

[B21]

Trying to get pad alignment on the discs perfect..getting hard work cutting these brackets out in steel so went for 3D printing purely for alignment purposes…

So the good news is that the 345mm version is now perfect with the pad sat nicely on the disc using all the pad and most of the disc..previously the top of the pad was just fractionally past the top flat part of the disc..

The 370mm version needs one more iteration as the front of the pad is siting fractionally lower than the rear..2mm adjustment on the front caliper bracket hole should see it..

Then ready to hand them over to the laser / water cutter buys to fab a few..

Interesting to see how much disc the original 300mm rear disc pad missed..

[RobbiZ4]

Great news!

Do you already have an idea, which material will be taken for the adapters? Maybe I can ask the German TUEV inspector about his view and requirements for such a solution.

Short summary:
- 345mm x 24mm (p/n 34216775289) rotors new from BMW cost about 130€ each.
- partnumbers of the rear calipers are 34216793047/34216793047? New from BMW 290€ each.
- brackets 34216793053/34216793054? New from BMW 240€ each.