F30 4 Pot Brembos on my 3.0si; the cursed build with no conclusion

[hq114]

I've come to the conclusion that this build is cursed; I simply cannot get it to work. My failing is almost certainly due to not doing enough research before getting started! It has however been an interesting learning experience, and I'm now much more confident at spannering on my car. I am however this close to just putting all the parts on Facebook marketplace and licking my wounds. If somehow, somebody can suggest how to make this work, I would certainly appreciate it!

Since I bought my yellow Z4, I've been wanting to update the aesthetic of the black MV2s with red calipers. The combo just doesn't work for me.



I loosely had the idea of "grey wheels and blue calipers" in my mind as the aesthetic to aim for. Step 1 was wheels; I put 400M F30 alloys on the car, retaining the stock wheel widths (and therefore my current tyres) and giving a more aggressive stance at the front. I was very pleased; they looked amazing;



With the idea that I would occasionally like to take this car on track, I wondered if I could upgrade to a beefier brake setup. I came across the notion of the 4 piston Brembo calipers from the F3x platform, combined with 340mm VW transporter discs (with enlarged centre bore), 1.5mm washers to shim the caliper outboard to centralise with respect to the disc, new braided HEL hoses. This is a modification that seemed to be tried and tested on the E46 platform, so I had the notion that it could also be made to work on the Z4.

I love the appearance of the brembo caliper and the blue they come in looks fantastic, so I bought a load of parts/tools and set to work. Starting with the driver's side, I bolted everything on and bled the new caliper. It looked great;



I popped the wheel back on....and it didn't turn. The spokes were fouling my freshly repainted caliper;



Having bashed away at the task for most of a day, I did not have the brainpower remaining to muddle through exactly where the root cause lay. So I spent a depressing evening returning everything to stock.

I had the notion that the magnitude of the issue was quite small, so I bought some 3mm spacers and tried again to mount the components (this time, tying the stock caliper to the strut and saving myself the pain of bleeding the system). Once again, the wheel didn't turn. I stacked 2 spacers taking me to 6mm, and yet again it wouldn't spin. Clearly the magnitude of the issue was actually quite large, but I was never getting to the stage of properly seating the wheel against the brake disc.

I decided that the dished nature of this new wheel was causing the problem (ET34 front offset). The sweep of the spoke from the centre bore to the outside is what was fouling against the caliper. What I needed was a slab faced wheel with more positive offset and less spoke angle, and to then use a larger, hub-centric spacer to clear the caliper. See below my finest Powerpoint engineering to illustrate my scheme;



Bye bye 400Ms, I will miss you. A good candidate would have been the MV2s that came off (front offset of ET47), but I'd already flogged them on Facebook Marketplace. Onwards and upwards! I found some Style 108s that came up for sale, and had my tyres moved across ready for my next attempt.



I decided on 15mm hub centric spacers for a few reasons;

• There is a 13mm offset difference at the front between the 400M (ET34) and Style 108 (ET47) wheels.
• Occasionally, the front tyres would rub against the inner arch on max compression when I had the 400Ms.
• I wanted to space out the Style 108 to put me in no worse a situation than the 400M.
• I could either go down to a 12mm spacer, or go up to a 15mm spacer.
• To give myself the best possible chance, I purchased a pair of 15mm MTEC hub centre spacers.

Once again, looks great, but still, the spokes clash with the caliper.



At this stage I'm completely bamboozled; someone on a Pistonheads forum put this exact brake setup on their Z4 with Style 108s;

2004 BMW Z4 3.0 - Page 4 - Readers' Cars - PistonHeads UK

I stacked every spacer I had on to the hub, just to see how far I need to go. With the 15mm hub centric spacer, x2 3mm shims, and also removing the penny washers that space out the caliper, the wheel finally turned. At this moment, I'm spaced out by 21mm, the caliper is no longer centalised to the disc, and frankly the stance is a little too aggressive. The wheel is protruding beyond the fender;



As compared to stock



Though the wheel now turns, the clearance is about a hair's breadth. I shoved a piece of paper into the gap between the wheel + caliper, turned the wheel, and tore the paper. My options going forward are;

• More aggressive spacing? I need at least 21mm, so the only option without going custom is 25mm. I definitely should not go to 25mm.
• Talk to the person who wrote the Pistonheads forum post; clearly there's something different about our setups that allows theirs to fit.
• Try another set of wheels.
• Give up and sell the parts; this option is sounding quite attractive.

The latest attempt was yesterday, so this concludes my tale of woe. Thank you for reading, if indeed you reached this far!

 

[B21]

When they launched the E89 a lot of detail was placed as to how much fiddling about and subsequent consequences of being able to fit bigger discs n calipers..

Those calipers bolt on a dream with 340mm 370mm 380mm discs on the E89

 

[Meds]

Those 4 pots are very wide, a popular upgrade with the 130i guys but wheel choice and/or spacers need research, as they foul so many wheel designs.

I went with the 6 pots, I luckily kept them from my previous 130i. IMO they look better as I was never a fan of the pill shaped 4 pots but that's just personal taste. My build thread has the details of what's needed.

Either option is worth the aesthetics alone. The stock brakes although work perfectly well just dont look great, especially behind a nice wheel.

You'll get there, keep at it...!

 

[Paul345]

I run Renault four pot Brembo on my 3.0si and use 15mm spacers. My alloys are MV2. I definitely wouldn't use a spacer over 20mm. I have come across some threads on the forum saying that using over 20mm causes shaking! My advice would be try a different wheel set up. Hope that helps you.

 

[3002 tii]

Couple thoughts come to mind...

1. Even if you got these calipers to fit under your wheels, have you done any calcs to see how brake bias will be impacted? It would be a kick to the nuts if you somehow got this to work but ended up with worse braking.

2. Are your wheels square or staggered? If staggered, have you tried test fitting the rear? You may still need a spacer but I imagine rears have more spoke clearance.

3. I'm confused why you said a wheel with higher offset such as the MV2 with et47 would've been better. I agree anything with less concavity would improve spoke to caliper clearance. But switching from et 34 to et47 + 15mm spacer basically gets you back to where started (ignoring difference in spoke design). Lower offset means more clearance on strut side.

4. Unless MOT has a thing against tires sticking out past the arches, that's not the worst thing in the world. Well stacking spacers isn't good but if you are planning to the track the car, a proper dedicated track wheel setup may end up looking the same. For reference, here's a pic of my old 3.0si coupe with 9.5" ARC-8s on all 4 corners. Tons of front end grip, car was very neutral.

If it were me, I would sell the brakes and get a proper kit designed for the car. Even the 135i 6 piston setup would be far easier to retrofit. But I'd have major reservations going on track with a brake setup that contains so many shims, spacers, etc.

 

[SteatoLegato]

I might be completely up the wrong tree here, but my understanding is that wheel offset indicates wheel position towards the centre of the car, i.e. the higher the offset the more the wheel is actually closer to the opposite wheel. So for your thingos, going from 34mm offset to 47 mm offset with 15mm spacer basically got you to where the 400Ms were to start with. You could have probably got a 10mm spacer with 400M and be clearing the caliper? again, apologies if this is just a brain fart

 

[hq114]

Hi everyone, thanks for the positive encouragement.

Couple thoughts come to mind...

1. Even if you got these calipers to fit under your wheels, have you done any calcs to see how brake bias will be impacted? It would be a kick to the nuts if you somehow got this to work but ended up with worse braking.

2. Are your wheels square or staggered? If staggered, have you tried test fitting the rear? You may still need a spacer but I imagine rears have more spoke clearance.

3. I'm confused why you said a wheel with higher offset such as the MV2 with et47 would've been better. I agree anything with less concavity would improve spoke to caliper clearance. But switching from et 34 to et47 + 15mm spacer basically gets you back to where started (ignoring difference in spoke design). Lower offset means more clearance on strut side.

4. Unless MOT has a thing against tires sticking out past the arches, that's not the worst thing in the world. Well stacking spacers isn't good but if you are planning to the track the car, a proper dedicated track wheel setup may end up looking the same. For reference, here's a pic of my old 3.0si coupe with 9.5" ARC-8s on all 4 corners. Tons of front end grip, car was very neutral.

If it were me, I would sell the brakes and get a proper kit designed for the car. Even the 135i 6 piston setup would be far easier to retrofit. But I'd have major reservations going on track with a brake setup that contains so many shims, spacers, etc.

This wheel style looks absolutely fantastic on your E86, the fitment looks great too. I definitely agree that stacking a load of shims and spacers before sending my car around a track is a bad idea; it was more a static test to ascertain the gravity of the clearance issue.

Here's the way I looked at the problem after the initial fit with the 400Ms. I needed to increase as much as possible the distance between the wheel-disc mating surface and the innermost point on the spoke that was smashing into the caliper, my "inside clearance"



I see your point about increasing my offset; in theory I am shooting myself in the foot going from ET34 to ET47 as I end up closer to the strut, and thereby worse off by being closer to the caliper;



My objective (which made sense in my mind was to go from ET34 to ET47, end up with a 13mm per side narrower stance, but with less concavity/spoke angle in the wheel design. Such that when I use a spacer, I can push the wheel back outboard enough for the spoke to clear the caliper, but avoid the situation of the stance being so wide that the outer edge of the wheel sticks out past the arch. Something like this;



This was the dream at least, it worked in my head but perhaps not in real life. The ideal design would be something like this;



Perhaps this exists, but I've frozen too many other parameters for my own good (18" wheels, 8j / 8.5j staggered setup) so my search has been limited.

Update; the guy on the Pistonheads forum responded to me, despite the fact that he has long sold his car. 25mm spacers are the way he got this setup to work with his Style 108 wheels. Once I can convince myself it is a good idea, I may well take the plunge.

 

[Meds]

Just as a side note. Wheel ET does'nt define how wide/thick the spokes are, it will give you an idea where the rim sits, not a measure on clearance behind the spokes, so be careful using ET as your measure. (it should get you fairly close though)

The only way to tell is to measure using a straight edge on the hub facing plate on the wheel and go from there with a perpendicular measure at the distance where the caliper fouls the wheel. (I've been here before)

The Fgen 4pot calipers are very wide from what I remember and you're far from the first to encounter issues when fitting them to E generation cars. I had 3mm clearance when I fitted them to a previous 130i.

A set of 135i E8x or 130i 'BMW Performance' 6pot brembos fit perfectly with an et34 wheel (loads of room) a carrier bracket and M discs.
And look far better than the 4 pots in my opinion.
Just sayin.

 

[B21]

Just as a side note. Wheel ET does'nt define how wide/thick the spokes are, it will give you an idea where the rim sits, not a measure on clearance behind the spokes, so be careful using ET as your measure. (it should get you fairly close though)

The only way to tell is to measure using a straight edge on the hub facing plate on the wheel and go from there with a perpendicular measure at the distance where the caliper fouls the wheel. (I've been here before)

The Fgen 4pot calipers are very wide from what I remember and you're far from the first to encounter issues when fitting them to E generation cars. I had 3mm clearance when I fitted them to a previous 130i.

A set of 135i E8x or 130i 'BMW Performance' 6pot brembos fit perfectly with an et34 wheel (loads of room) a carrier bracket and M discs.
And look far better than the 4 pots in my opinion.
Just sayin.

Man speaks the truth…

 

[Tncdrew]

Update; the guy on the Pistonheads forum responded to me, despite the fact that he has long sold his car. 25mm spacers are the way he got this setup to work with his Style 108 wheels. Once I can convince myself it is a good idea, I may well take the plunge.

I'm not sure your wheel bearings are going to like that....

 

[3002 tii]

My objective (which made sense in my mind was to go from ET34 to ET47, end up with a 13mm per side narrower stance, but with less concavity/spoke angle in the wheel design. Such that when I use a spacer, I can push the wheel back outboard enough for the spoke to clear the caliper, but avoid the situation of the stance being so wide that the outer edge of the wheel sticks out past the arch. Something like this;

View attachment 282612

Honestly, I've re-read your post three times and my only takeaway is that you overcomplicated this. The above snippet is what sticks out the most. Yes, going from et34 to et47 "pushes" the wheel inboard (i.e., sits inside closer to strut) by 13mm. But it does so by taking up 13mm of clearance between the hub and wheel, which is where your caliper sits. I know you said you added a 15mm spacer but let's hypothetically say it was 13mm for ease. Then all you've done is basically gain some tiny clearance by going from a concave spoke (style 400) to flatter spoke (style 108), but you largely still have the same issue. How do I know that? Because you said in your first post that even with stacking (2) 3mm spacers, you still could not rotate the wheel. And its unlikely you gained 6mm from going to a 'flatter' wheel spoke.

Easiest thing to do is to is add a thicker spacer to front with your Style 400s. If 6mm didn't work, try 10, 12, 15, etc. If you want to eliminate the guessing game, get a ruler or caliper gauge. Once you've determined which thickness you need, then see if you can get by without rubbing the fenders (because the wheel will now stick out more than before). And depending on degree of fender contact , you can then decide to remedy by one of 3 ways:

1. Alignment - add some negative camber
2. Tires - run shorter/narrower tires
3. Fender - try rolling the fenders

But when a wheel/brake setup is this poorly fitting, that's usually a sign. I'd go with a tried and true setup like the 135i 6 pistons and call it a day.

 

[tiglon]

Three options really - change wheels, change calipers or add huge spacers.

I'm getting the feeling you don't want to change the calipers, and no one really wants to add huge spacers, so option 1 might be the most attractive.

If you're changing the wheels, you need 72.6mm centre bore (or different but get a spacer that adapts this, or get small CB and get it bored out) and 5x120 bolt pattern. Obviously a (quite significantly) lower ET and/or a particular spoke angle/curve as well.

Here's a list of cars that use 5x120 bolts https://www.wheel-size.com/pcd/5x120/#google_vignette - not sure if it's comprehensive or 100% accurate, so double check before committing to anything, but it's been helpful for me in the past. There are loads of BMW options there, I'm not sure whether E85's are ok with a square setup, but perhaps it's worth looking at whether something like 4 x front 437m would work? Much lower offset (ET30 I think?), spoke curve looks favourable, and I'm sure I've seen them on an E85 before.

To be honest though, that doesn't give you much more clearance than the first wheels that didn't work. So, it may be that you're best off changing the calipers. Shouldn't cost too much to sell them on ebay and find a set of the 6-pots suggested?

Or maybe you can get a set of 4 front Lambo Revuelto wheels, get the CB made slightly larger and squeeze them into the arches? They're ET20...

 

[B21]

It’s hardly surprising there’s an issue with the F series calipers..as their name implies they were for the F series…it’s a push to get them on E9x platforms..E85 I guess is a bridge too far ..the 6 pot Brembos as fitted the E90s are the go to solution..

 

[Mr Tidy]

I don't know if it helps but plenty of E90 18" staggered wheels have an offset of ET34 on the front.

I fitted a set of E89 Style 295s to my previous Coupe and didn't get any rubbing. They are staggered 18s and the fronts are ET29.

 

[Darkangelv2]

Going back to the beginning, you said you'd fitted the exact same solution as in this post:

Pistonheads | 2004 BMW Z4 3.0

But you haven't?

He used a set of 345MM BMW M3 CSL discs - you've used VW Transporter discs. Surely that will be where your offset difference is coming from?

 

[Darkangelv2]

Going back to the beginning, you said you'd fitted the exact same solution as in this post:

Pistonheads | 2004 BMW Z4 3.0

But you haven't?

He used a set of 345MM BMW M3 CSL discs - you've used VW Transporter discs. Surely that will be where your offset difference is coming from?

Looking at the disc dims i can see they're basically the same.

I just re-read your post that mentioned the Pistonheads OP told you he used 20mm spacers. This makes the most sense as the bell height difference between original BMW M4 discs & BMW E46 CSL discs is 20.6mm.

M4 Disc:

CSL Disc:

 

[damocell]

441m wheels with a 10 or 15mm speacer fit these calipers on the Z4 with a stock 325mm 3.0si disc hat height....plus they look better than the 400m's. I sent a caliper to Matt Scarbro on here and he test fit it with his 441m's

Your issue is the hat height difference between the 340mm f series discs and the T5 discs with spacers. Correct this difference and you should fine with the 400m wheels.

Alternatively, fit the 340mm discs from a F20/30 with an adaptor kit and give it a try.

I tried fitting these F30 Brembos to my car and ran into the same problem. Issue for me is I am running Style 32's which have spokes that are more inboard than the 400m's. Also I didn't want to increase unsprung weight with such an unnecessarily large disc. I'll be fitting Brembo calipers from a Clio 197 soon to my 3.0si. Slightly smaller caliper and will allow more/easier disc options too.

 

[3002 tii]

Did this ever get resolved?

 

[Nathan88]

This thread was sadly over complicated.

F80 calipers can be fitted, but as the OP showed, it’s both offset AND wheel/spoke design dependant.

Here’s some fitted to my e86 with an ET32 replica CSL wheel (ET38 with a 6mm spacer) with room!

However, my ET29 BBS LM style wheel didn’t fit (ET35 with 6mm) which shows it’s not always straight forward.

I wouldn’t encourage anyone to be buying brand new discs or shelling out £300/400/500 on calipers unless you’re confident the set up will fit.

Video on my Instagram (z4coupeuk) which may help others on the future.

P.s I sold my set up because I’d need to raise my car in order to run sub ET35 front wheels and I’m not a fan of big arch gaps. If you’ve only lowered your car by 25/30mm you’d be fine - as the original guy in the PistonHeads thread with the burgundy red convertible appeared to be, which is where I first saw that it was possible.

 

[Meds]

Here’s some fitted to my e86 with an ET32 replica CSL wheel (ET38 with a 6mm spacer) with room!

However, my ET29 BBS LM style wheel didn’t fit (ET35 with 6mm) which shows it’s not always straight forward.

Yes, this confirms what I mentioned above. Wheel ET doesnt give a firm indication how deep the spokes are, or their distance from an imaginary line running parallel to the wheel/hub mounting face.

Generally the more aggressive it is, the more room you'll have, but it's not accurate and not a risk i would take before buying expensive components.
The only way to check before committing, is a measurement. I started a thread a while back trying to understand if a certain wheel design had enough spoke gap to clear the 135i 6 piston calipers, there's some info on there.
In the end I found the BMW 405 wheel fit with loads of room, maybe because they're forged so have thinner spokes?

The F series 4 piston calipers are really wide and finding wheels to clear them is a struggle.