8 piston Front Brakes for Z4M?

[FD3S]

I’m in the middle of fitting BMW 6 piston calipers on my M. They are a performance calipers for a 135i or 3 series i believe and is a fairly easy conversion. You have to get a custom carrier and longer brake hoses but they use the standard Z4 M disc

Those BMW performance seem really good. Let me know please when you fit them, your comments. Thank you.

I have had the BMW performance calipers fitted for 3 years or so now,and find them a very good improvement over the standard M brakes.
They stop better and resist fade alot better than the standard ones,and I got mine at a very good discounted price from a bmw dealer called Sopers,along with the performance brake pads to go with them.
They are basically the brembo gt2400 kit,which costs round £2,400 in the UK when I priced mine....I got the bmwp Calipers ,bmwp pads and new z4m discs as well as custom CNC machined caliper carriers,and custom braided stainless steel hel brake hoses,for under £900 in total,plus fitting
The only thing is you need to fit (hubcentric)12mm Spacers ,so they clear the Calipers,as they don't clear the standard z4m alloys otherwise
Big improvement on Standard,imo

Thank you Craig for you review.Price has a big difference compare it with Brembo indeed.

 

[Beedub]

Stock brakes in your case OP sound like they are more than adequate with a fluid and pad change, and braided lines if you choose too.

This, as Bee said, the Stock OEM claws are actually pretty darn good, and pretty darn effective with the right pads and fluids. Loved mine before upgrading.

So true. I never race the car, so the brakes almost never heat up so much or don't have enough power to stop the car. They stock brakes are very good for me, up to the moment. The only reason I am thinking of it since I need to upgrade the discs, and the same time I am saving so I can go with the SC way. Beedub do you believe someone with SC needs, brake upgrade with SC?

ideally yes..... but again depends on how you plan to use them.... ive still managed to see the front rotors glow red hot with the added firepower of the blower., Then again i remember the stock brakes just about managing with the stage 1 kit and smart braking when on it. The stock brakes on this car were excellent as i remember them.

 

[craig3.2]

Those BMW performance seem really good. Let me know please when you fit them, your comments. Thank you.

I have had the BMW performance calipers fitted for 3 years or so now,and find them a very good improvement over the standard M brakes.
They stop better and resist fade alot better than the standard ones,and I got mine at a very good discounted price from a bmw dealer called Sopers,along with the performance brake pads to go with them.
They are basically the brembo gt2400 kit,which costs round £2,400 in the UK when I priced mine....I got the bmwp Calipers ,bmwp pads and new z4m discs as well as custom CNC machined caliper carriers,and custom braided stainless steel hel brake hoses,for under £900 in total,plus fitting
The only thing is you need to fit (hubcentric)12mm Spacers ,so they clear the Calipers,as they don't clear the standard z4m alloys otherwise
Big improvement on Standard,imo

Thank you Craig for you review.Price has a big difference compare it with Brembo indeed.

Cheers
I don't do track days in my car either,but just wanted a better biting brake set up and one that didn't fade as easy as I felt the standards brakes did.
I do go on some spirited runs,where the brakes do get a bit of a workout,way more than in normal/daily driving.
I like the bmwp kit,just changing my pads and discs shortly,after over 3 and a bit years and circa 16,000 miles.
Not alot of lifespan compared to some,but as said,they do get regular workouts,lol

P.s,Look on m3cutters for a thread about this bmwp brake setup for E46 m3's.....he does the brackets for Caliper carriers, CNC machined from billet aluminium,by an engineering company,and does the braided stainless steel hoses custom made (longer) all in one package.
Can't remember his name,but will try and find out.
They fit teh z4 well,given it uses the CSL M3 brakes
Hope this helps,if you decide to go down this route,op

 

[GuidoK]

Lol, they are nothing like the brembo GT kit!! Those calipers are a world apart from those used for the bmwp calipers.

What is so different about them?
Both are single block cast with integrated stiffinging bridge (which gives more stiffness than a caliper made up from 2 halves that is bolted together), 6 piston with increasing bore size to reduce padwear and equipped with dustboots. There is a difference in padsizes, but the bmw performance pads are stil way bigger than the ones in a Stoptech or AP BBK.

I've had the BMW/Brembo performance calipers on my car (both front and rear ones) for over 6 years, and they are excellent.
In Germany this is also a very popular mod. I was at the german international meet in Nürnberg a month ago and I probably counted 20 sets or so.

 

[ga41]

I would also skip buying the R8 callipers too mate. I've also not seen anyone use E9x M3 front discs on our cars either but then again it doesn't mean it didn't happen. Are the bell size and shape, ring offset etc OK? Mechanics say a lot of things...

At least the BMW Performance option is tried and tested by many people but as we already discussed my preferred way would be to save up more and get a proper kit if you want a BBK.

If you need new discs but are saving up for a BBK later on then I wouldn't worry as I think you would be able to sell your OEM discs very easily online!

 

[craig3.2]

Lol, they are nothing like the brembo GT kit!! Those calipers are a world apart from those used for the bmwp calipers.

What is so different about them?
Both are single block cast with integrated stiffinging bridge (which gives more stiffness than a caliper made up from 2 halves that is bolted together), 6 piston with increasing bore size to reduce padwear and equipped with dustboots. There is a difference in padsizes, but the bmw performance pads are stil way bigger than the ones in a Stoptech or AP BBK.

I've had the BMW/Brembo performance calipers on my car (both front and rear ones) for over 6 years, and they are excellent.
In Germany this is also a very popular mod. I was at the german international meet in Nürnberg a month ago and I probably counted 20 sets or so.

Well said,GuidoK

 

[TomK]

Lol, they are nothing like the brembo GT kit!! Those calipers are a world apart from those used for the bmwp calipers.

What is so different about them?
Both are single block cast with integrated stiffinging bridge (which gives more stiffness than a caliper made up from 2 halves that is bolted together), 6 piston with increasing bore size to reduce padwear and equipped with dustboots. There is a difference in padsizes, but the bmw performance pads are stil way bigger than the ones in a Stoptech or AP BBK.

I've had the BMW/Brembo performance calipers on my car (both front and rear ones) for over 6 years, and they are excellent.
In Germany this is also a very popular mod. I was at the german international meet in Nürnberg a month ago and I probably counted 20 sets or so.

Where to start? The weight is 5.1 kg for the bmp calipers which is pretty much as heavy as the stock item I think? The AP 5575 caliper I use weighs 2.7kg, I believe the GT is slightly more.
The caliper definitely has problems with dispersing heat, under very hard use (lines, fluid and pads all the same in both of my kits) the difference in feel between the bmwp and ap kit is very noticeable. After some hard lapping the pedal loses feel and it is not hard to make them fade, on the north loop I expect they'd be ok, on the gp circuit not so much.
I haven't driven a brembo Gt equipped car to be fair, but I suspect the differences will be similar to what I experienced moving to AP. In concept I think you're right in that the bridge should make them stiffer, in practice it felt anything but to me compared to the AP.
To change the pads on the bmwp calipers is a ball ache, caliper off, whereas with AP or the GT kit (I think) it's a matter of minutes.
The caliper is bulkier than most BBKs and consequently often spacers are required depending on your wheels of course.
The pistons that are supplied with the caliper (admittedly this is fairly easy to upgrade) are not great, known to crack, and the seals after a session on track will be ruined, in my experience. I also found pad wear across the front to back to be quite uneven pointing towards poor pressure distribution by the pistons.
Perhaps most importantly you are limited to the 28mm disc width (and to a lesser extent the 345mm diameter).
All that said, they are designed as a road car caliper for a 135i and they do a pretty fantastic job at that for sure, it's when they are put under serious use that the difference between this kind of budget caliper and the ones that cost 4 times as much become apparent, but that is only to be expected surely.
I would agree that they are a big improvement over stock on the road, lovely feel, but if you're going to spend all that money... buy cheap, buy twice... All depends on what you want to do with the car though I guess

 

[TomK]

I've also not seen anyone use E9x M3 front discs on our cars either but then again it doesn't mean it didn't happen.

It has been done, albeit on e46m3.
Some people use the m performance M135i calipers with them, I believe the 360 mm disc needs to be turned down to 357mm, not hard for a shop to do.
I would think it is all possible with the R8 caliper, but it's worth pointing out to the shop that the Z4M/E46m3 fitment is very slightly different (2mm or so on the offset of the disc or something like that).

 

[Bodyboarder]

So who on here does run the Bmw performance calipers with the standard discs? Would like some first hand experience and pics if possible ? I’d love to get a set for my road going M and from all of the above seems they would fit the bill nicely

 

[TomK]

So who on here does run the Bmw performance calipers with the standard discs? Would like some first hand experience and pics if possible ? I’d love to get a set for my road going M and from all of the above seems they would fit the bill nicely

You can only run them with the standard disk afaik

 

[GuidoK]

Where to start? The weight is 5.1 kg for the bmp calipers which is pretty much as heavy as the stock item I think?

Its not that heavy. The packing weight info from bmw is not correct.
I'll measure the exact weight when its on the lift again and we'll see how far you're off.
It can be lightened by ~700gram by removing the anti resonance weights. See the german forum for extensive info on this mod.
But it will be heavier than the AP caliper because, as I said, the pad in the BMW/Brembo caliper is considerably larger than the pad in the CP5575, both in lenght as in width. Because the width is also slightly larger, the overall disc diameter can be smaller to achieve the same disc area resulting in a smaller rotational inertia of the disc.

The caliper definitely has problems with dispersing heat, under very hard use (lines, fluid and pads all the same in both of my kits) the difference in feel between the bmwp and ap kit is very noticeable. After some hard lapping the pedal loses feel and it is not hard to make them fade, on the north loop I expect they'd be ok, on the gp circuit not so much.

I havent had any of these problems but then again, its a combination of pads, fluids and discs. Maybe you had an unfortunate combination. And on the german forum no one experiences these problems, so I think this is more an individual problem than a general problem. Anyway if desired the pistons can be changed to stainless very easily from suppliers like RB (the piston diameters are fairly standard, so also silicone seals are available)

It is proven that calipers made from 1 piece with fixed halves and a fixed bridge is way way stiffer. Look at formula 1 were costs and manufacture difficulties play absolutely no part: NO caliper is made up of 1 bolted halves. they're all one piece.

Swapping pads on a 1 piece caliper is not that much of a pain as you make it seem to be.
First you have to remove the wheel: thats 5 bolts. You have to do that either way (jacking up the car etc etc)
Getting the caliper off is an extra 2 bolts. Thats all and you can get the pads out.
I dont think 2 extra bolts is that much of a problem? (actually the bridge of a 2 part caliper is also bolted so its hardly any extra work....)


The maximum thickness for the discs is I think about 30mm. Sure a bigger caliper can use thicker discs, but do you really want all that extra unsprung extra rotational weight? on a 1300kg car?
The /m discs are very very well race proven. Even professional race classes with z4's have used them. (again see the german z forum, there's a professional racing driver active there from the schmickler racing team, having raced z4's, on occasion even with the stock brakes, if the track allowed it: again: less rotational weight is better).

 

[TomK]

You make some fair points Guido and I'm happy you get on well with yours. Though having run both myself, and if I could do it all again, I'd have just bought the APs first time round.
You picked up on my original point that the GT calipers are a far superior item, do you really believe that not to be the case?

 

[GuidoK]

You picked up on my original point that the GT calipers are a far superior item, do you really believe that not to be the case?

In what way would they be superior?
Having a larger pad? maybe.
But I dont think they're very much lighter or stiffer in construction. To be clear: having a heavier caliper means more material is gone into the construction thus making a stiffer caliper if the padsize is the same. And all these calipers are of similar material, none of them is magnesium or other exotic alloy. This is still all fairly simple consumer grade stuff, cast aluminium. none of them are billet milled or so (that would be way way more expensive)
If an aluminium caliper is heavier its either larger or stiffer imho. Wether either one is necessary is under debate. The bigger the pad, the more stiffness you need, but for that you do get a bigger pad with all its benefits (look at F1 with crazy pad/discsize ratios)
One of the major differences in the BMW Performance calipers is the use of anti resonance weights (and they do add weight, otherwise they wouldnt work ). But that is an individual choice, I've seen these weights also on the more exotic ferraris like stradales etc (equipped with brembo gt above brake systems :wink: ), so apparantly this is an accepted way of doing things, trading less unsprung weight for more stability. But those weights are all removable, so its a choice.

The 2 things that could be more race oriented with the BMW Performance calipers is the use of stainless pistons and silicone dustseals.
But this might be a deliberate choice; the BMW Performance calipers are used on street cars; OEM. And especially the silicone dustseals are not durable. So that requires very frequent checking up, like every 6 months to see if the dust boots are still not torn. No biggie on a racecar (or trackcar), were pads are changed every month or so, but on a streetcar it can be years for changing out pads, certainly with our limited use.
Anyway, stainless pistons and silicone boots are easily available for the BMW performance calipers for little money if they would be needed, solving all heat problems.

 

[MrPT]

Another reasonably priced upgrade option is 4-pot DB9 or last-gen TTRS front calipers, plus brackets from Vagbremtechnic. They are Brembo 44/40 so a very close match for the stock piston area and have quick release pins so you can swop pads easily if you need to. Weight is 2.95kg, excluding pads.

Downsides are that there isn’t an obvious rear option and spacers are needed for them to clear 224s or CSLs. They also don’t come up that often second hand, so if you’re looking for a real bargain and can’t wait, you might be better off with the Porsche Boxster S/996 option.

 

[GuidoK]

TBH if I would need to buy a BBK now it would be from D2 racing (no need to break the bank and buy 2700 pound bbk's imho).
I know multiple people who have them to full content.
They have excellent sets fully configurable, even with fully floating discs if a serious track setup is needed. If I look closely at the drawing from the AP 6 piston BBK, even that doesnt have a floating setup. (maybe thats available at an extra ).
BMW M discs are semi-floating btw so not your average disc.

When I installed my BMW performance BBK over 6 years ago, I spent around 1400 pound for the front&rear together (that includes new calipers, pads and M discs).
True the rears I had to make myself using the performance calipers and a mix of parts, but 6 years ago nothing was available anyway for the rear.
Sadly now all BBK's that are based on the BMW Performance calipers have increased immensely in price but back then this was all quite new and not so popular so prices were very low. The rear calipers I got (new!) for about 80/piece, probably because the tuner that made the BBK's bought complete bmw caliper sets and the rear ones started to pile up so they sold them cheap with the catchphrase "for hobbyists that like to try something different" (that would be me I thought )

 

[TomK]

You picked up on my original point that the GT calipers are a far superior item, do you really believe that not to be the case?

In what way would they be superior?

In the alloy used I'd most likely expect. You say there'snot much difference in materials used, I'm not so sure.
Do you think that the GT caliper (which I believe weighs around 2kg less) is less stiff than the BMWP caliper? Why would they do that? Or more to the point, why would they make the BMWP caliper so stiff and (all things being equal) therefore so heavy for a road car application?

 

[GuidoK]

In the alloy used I'd most likely expect. You say there'snot much difference in materials used, I'm not so sure.
Do you think that the GT caliper (which I believe weighs around 2kg less) is less stiff than the BMWP caliper? Why would they do that? Or more to the point, why would they make the BMWP caliper so stiff and (all things being equal) therefore so heavy for a road car application?

Why would the gt calipers be of another alloy? You have any verifieable data on that?
If not thats not a real argument but a loose specification. 50% chance, either it has or it hasnt
And in that view the BMW performance calipers could also have a better alloy and even be much stiffer. Again 50% chance

And I'm not so sure the GT calipers are 2kg lighter. Where do you get that data? first hand?

and the 2,7kg for the ap calipers, you've measured that first hand? pics?
And is that with pads? without? with brackets? without? with bolts? without?

I see a lot of numbers presented as 'facts', but no verifieable data to back that up or what those numbers actually present. It makes the discussion only very vague and not clear if apples are compared to apples and not pears.

 

[Bodyboarder]

I’d really like info on the bmwp set up front/rear !

Spacers required for fitment over 19” csl reps 8.5 et40 ?

Where to purchase the calipers , fitting kit ect

What was used for the rear calipers ? And where to get it all ?

They would fit my needs perfectly and look the part too

 

[GuidoK]

you can get the seperate brackets for front bbk's from epytec.de

For the rear I've used a mix of bmw e46, e83 and e60 parts, all adapted (lathe,tig welder etc) and custom caliper spacer rings
I believe on the german forum they had an e82 disc adapted with a cast iron ring inserted in the drum a while back (and obviously adapted the backing plate)
So these are not bolt-ons, but doable if you have machining skills.

 

[TomK]

Why would the gt calipers be of another alloy? You have any verifieable data on that?
If not thats not a real argument but a loose specification. 50% chance, either it has or it hasnt
And in that view the BMW performance calipers could also have a better alloy and even be much stiffer. Again 50% chance

I don't really get what you're on about here? If you have two objects ostensibly the same size and one of these weighs let's say conservatively 25% less the inference has to be that the material makeup of them is different. You can then extend that to saying the lighter one has to provide the same job as the heavier one, inference being that the material is also stronger. I find it highly unlikely that Brembo would use an inferior makeup for their GT calipers that are used in race cars far far more often than BMWP calipers for sure!

The maximum thickness for the discs is I think about 30mm. Sure a bigger caliper can use thicker discs, but do you really want all that extra unsprung extra rotational weight?

The weight of the 356mm AP disc is actually a couple of hundred grams lighter than the Z4M disc, thank the aluminium hat for that I guess.

And I'm not so sure the GT calipers are 2kg lighter. Where do you get that data? first hand?

Not first hand no, best info I can find is from Sharkworks who say without the bracket and pads caliper weighs 3.4kg. I think Vanne on here has a set of these from an American Z4M owner, perhaps either of them weighed the calipers ever and could verify?

and the 2,7kg for the ap calipers, you've measured that first hand? pics?

Again no, but AP specify that (without pads) and I don't think they're really in the business of lying. Besides it would be pretty easy to check.
I remember having both the AP and bmwp calipers in either hand when swapping them and twice the weight felt about right to me.
Next time you have yours off Guido get them weighed, it would be interesting to see how wrong I am

I havent had any of these problems but then again, its a combination of pads, fluids and discs. Maybe you had an unfortunate combination. And on the german forum no one experiences these problems, so I think this is more an individual problem than a general problem.

There's quite a few over here and in the US I see on forums who have had similar issues, maybe it's a German thing?

It's a nice kit the BMWP but it is a kit built to a budget and usage profile set by BMW. It's certainly not up to the quality/standards of say the Brembo calipers made to Porsche specs, and for sure not their own GT kit (or even that R8 caliper perhaps for that matter :lol: ). That's why they're cheap.