Best retrofit for M3 brakes?

Grip Addict wrote

Why hasn't anyone figured out a way to get the 4 pot Megane Brembos on the rear yet?

I would totally jump on a retrofit BBK, but my OCD cannot have the fronts having a BBK and the back stock.

Captain Caveman wrote

Grip Addict wrote

Why hasn't anyone figured out a way to get the 4 pot Megane Brembos on the rear yet?

I would totally jump on a retrofit BBK, but my OCD cannot have the fronts having a BBK and the back stock.

The piston area of the Megane Brembo is waaaay too big to use on the rear of the M3. If you used that caliper on the back it would massively alter the front/rear bias, shifting it rearwards enormously, and would give you a very long, mushy pedal due to the big overall increase in fluid you'd need to push to deploy the pistons.

The e92 M3 has a total rear piston area per caliper of 1661mmx2, whereas the Megane and Clio calipers have a piston area of 2512mmx2, which is 50% larger.

Epoustouflant wrote

Have you looked at the numbers on the C63 retrofit front and rear?

Captain Caveman wrote

Epoustouflant wrote

Have you looked at the numbers on the C63 retrofit front and rear?

Yep. Front piston area is too big, and rear piston area is too small. Also the calipers are designed for much thicker discs, so not ideal with stock e92 discs as they are quite thin:

C63 AMG (W204) front - 34/36/38mm - 3059mm x 2 per caliper
C63 AMG rear - 28/30mm - 1322mm x 2 per caliper

The Alfa calipers front and rear are a better bet, as not only are the piston sizes a perfect match for the stock m3 master cylinder, but they are also designed for smaller discs that are closer to the stock thickness and smaller disc diameter. They would also work perfectly with M4 discs.

Epoustouflant wrote

The 6 pistons Quadrifoglio front calipers are very difficult to find though - are you referring to the 4 or 6 pots?

Captain Caveman wrote

Epoustouflant wrote

The 6 pistons Quadrifoglio front calipers are very difficult to find though - are you referring to the 4 or 6 pots?

The 6-pot Brembos. Normally available in Europe on eBay and shipping shouldn't be too bad.

https://www.ebay.co.uk/itm/2018-Alfa-Romeo-Giulia-Quadrifoglio-Pair-Of-Brembo-Front-Brake-Calipers/193140707894?_trkparms=aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D225076%26meid%3D9ce0261ce21940ea992b8ab49fcef18e%26pid%3D100012%26rk%3D3%26rkt%3D12%26sd%3D184457156990%26itm%3D193140707894%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DSimplAMLCvipPairwiseWebWithBBEV2bDemotion%26brand%3DAlfa+Romeo&_trksid=p2047675.c100012.m1985

Epoustouflant wrote

That's one of two that are available though, doesn't seem like a realistic commercial option for our cars.

Captain Caveman wrote

Epoustouflant wrote

That's one of two that are available though, doesn't seem like a realistic commercial option for our cars.

The front Maserati 6-pot Brembo is identical and should be easier to source in the US. It's used on the Granturismo, Quatroporte and Ghibli and has the same 30/34/38mm piston size and is radius mount allowing for simpler custom bracket fabrication.



https://www.ebay.com/itm/Maserati-Quattroporte-Ghibli-Front-Right-Left-Brembo-Brake-Calipers-Set-OEM/264920120848?fits=Make%3AMaserati&hash=item3dae783e10:g:sygAAOSwAiVfngzp

Captain Caveman wrote

The front Maserati 6-pot Brembo is identical and should be easier to source in the US. It's used on the Granturismo, Quatroporte and Ghibli and has the same 30/34/38mm piston size and is radius mount allowing for simpler custom bracket fabrication.

https://www.ebay.com/itm/Maserati-Quattroporte-Ghibli-Front-Right-Left-Brembo-Brake-Calipers-Set-OEM/264920120848?fits=Make%3AMaserati&hash=item3dae783e10:g:sygAAOSwAiVfngzp

W12x wrote

The Maserati one is probably the easiest to find radius mount Brembo 6 pot in the US.

How much harder is it to make custom bracket for the non-radius mount? GM have good calipers (from ZL1, other Camaros, etc) with non-radius mount, lots of them and doesn't cost much, not sure about the piston size tho.

(I remember reading somewhere on this forum that Mustang's caliper piston size isn't a good match)

Captain Caveman wrote

W12x wrote

The Maserati one is probably the easiest to find radius mount Brembo 6 pot in the US.

How much harder is it to make custom bracket for the non-radius mount? GM have good calipers (from ZL1, other Camaros, etc) with non-radius mount, lots of them and doesn't cost much, not sure about the piston size tho.

(I remember reading somewhere on this forum that Mustang's caliper piston size isn't a good match)

All the GM options (ZL1, ZR1, Z06, CTS-V) use a near identical 6-pot Brembo caliper, which shares the same piston size configuration (30/34/38mm), but the spacing of the lugs make it impossible to fit with a spacer/bracket.

The only way to use these calipers is to have the lugs machined off, and then the caliper drilled to radius mount. Not a simple or cheap undertaking as it requires a precise CAD drawing of the caliper and CNC machining skills.

Much simpler and cheaper just to use a caliper that's already radius mount like the Alfa or Maserati one. Practically plug and play in comparison.

Captain Caveman wrote

W12x wrote

The Maserati one is probably the easiest to find radius mount Brembo 6 pot in the US.

How much harder is it to make custom bracket for the non-radius mount? GM have good calipers (from ZL1, other Camaros, etc) with non-radius mount, lots of them and doesn't cost much, not sure about the piston size tho.

(I remember reading somewhere on this forum that Mustang's caliper piston size isn't a good match)

All the GM options (ZL1, ZR1, Z06, CTS-V) use a near identical 6-pot Brembo caliper, which shares the same piston size configuration (30/34/38mm), but the spacing of the lugs make it impossible to fit with a spacer/bracket.

The only way to use these calipers is to have the lugs machined off, and then the caliper drilled to radius mount. Not a simple or cheap undertaking as it requires a precise CAD drawing of the caliper and CNC machining skills.

Much simpler and cheaper just to use a caliper that's already radius mount like the Alfa or Maserati one. Practically plug and play in comparison.

W12x wrote

Thanks for explaining it!

I was just curious since GM calipers have very steady supply, and Maserati is much easier to find than Alfa but still not readily available like the American ones

pbonsalb wrote

One advantage of the “staged” BBK is that you don’t have to spend all the money up front. You can use up your stock rotors and then buy 2 piece if you will stay 360mm.

Captain Caveman wrote

Yes, this is definitely an option, but does require the use of calipers that were originally designed for slimmer discs. Using a caliper that was intended for 36mm discs on a 30mm thick disc, for example, could cause issues.

Maxroach wrote

Captain Caveman wrote

Yes, this is definitely an option, but does require the use of calipers that were originally designed for slimmer discs. Using a caliper that was intended for 36mm discs on a 30mm thick disc, for example, could cause issues.

Like what issue/s?

Also, how/when can you determine what rotor thickness can you use on caliper that intended to use 36MM thick rotors?

Just curious..

Captain Caveman wrote

I have been doing lots of research into doing a properly matched BBK retrofit, with calipers that have as close to stock piston area and front/rear bias as possible.

My first consideration was the F8X setup as it would seem a no brainer, however despite the relatively simple fitment, I've realised that the M4 has a 10% smaller total piston area than the E92 M3, which means a 10% firmer pedal with 10% less modulation, and 10% less torque at the piston.

Here are the caliper stats side by side:

E92 M3 calipers
Stock M3 piston area front 60mm - 2826 x 2
Stock M3 piston area rear 46mm - 1661 x 2
Stock M3 total area 4487
Stock front bias 63%

M4 calipers
F8X M3/M4 front BB-43 (40/40x30mm) - 2512 x 2
F8X M3/M4 rear BB-22 (44x24mm) - 1520 x 2
Total 4032 - 10% firmer - Stock bias 62%

Ideally you want to find calipers that maintain the total piston area to match the capacity of the master cylinder. If you compare the E92 specs with even the Stoptech setup, we can see that even they deliberately only differ total piston area by 1% and shift the bias slightly rearward:

Stoptech BBK
Stoptech non Trophy st60 front = 36/36/30 - 2741 x2
Stoptech Trophy ST60 32/34/36mm = 2729 x 2
Stoptech st40 355 back = 34mm 32mm - 1711 x 2
Total 4452 or 4440 x2 / 1% harder 61.5 front bias

To keep as close to stock piston area, ideally you need to find a combination of front and rear that are RADIAL mount to allow for easy bracket fabrication, NOT lug mount. Ideally with the following piston configurations, :

Front 6 Pot
32/34/38mm - 2845 x 2
30/34/38mm - 2748 x 2
30/36/36mm - 2741 x 2
32/34/36mm - 2729 x 2

Rear 4 Pot
34/32mm - 1711 x 2
30/34mm - 1614 x 2
32/32mm - 1608 x 2

Hope that's useful.

Mart.

Captain Caveman wrote

E92 M3 calipers
Stock M3 piston area front 60mm - 2826 x 2
Stock M3 piston area rear 46mm - 1661 x 2
Stock M3 total area 4487
Stock front bias 63%

Captain Caveman wrote

Front 6 Pot
32/34/38mm - 2845 x 2
30/34/38mm - 2748 x 2
30/36/36mm - 2741 x 2
32/34/36mm - 2729 x 2

SAMM3Y wrote

I would imagine you're in danger of the piston popping out when the pad/rotor wears thin or reaching its max travel.

Maxroach wrote

Really good info here.. Thank you.

Just a few questions,

Stock M3 piston area front is 2826 x 2 calipers, right? one piston each caliper and each side.

And these for example, 6 pistons with 32/34/38 is 2845 x2 also per caliper?

1 caliper OEM is 60mm which is 2826

vs

1 caliper 6 pistons is 32/34/38 at 3 pistons each side is 2845, so 1 caliper is 2845 x 2 which is 5690 per caliper?

Just curious.

pbonsalb wrote

The calculations treat the stock single piston sliding calipers as if there is a piston on each side. Consider it a dummy piston.