F8X Brembo BBK Swap on E46 M3

[clawhamm3r]

Is that based on Mk 60 brake bias?

It was later determined that MK60/20 rear pistons didn't matter in the equation...can't remember why. Something to do with proportioning valves and equal pressure, or true north and climate change..something like that. p0lar even said all of his original charts were wrong because they calculated for that and put disclaimers on his original post in *the* brake bias thread. And that one dude in another thread (maybe streamline thread?) hooked a raspberry pi up measuring outputs form both MCs and confirmed this.

Also his (p0lar) charts had a pad friction coefficient....we all collectively agreed we could ignore that because we know different compounds have different friction coefficients. If we just want to calculate straight bias based on caliper/piston/rotor sizes (which is what we love to debate on the forums), then we can ignore that as well.

Finally, he was also factoring in for leg strength lol. Once again, if we just want to focus on the parts that would be changing for our cars with everything else equal, we can drop that variable (make it a 1?) in the equations and a very different brake bias picture begins to take shape.

Enter me during the Streamline DB9 debates, all I did was gather all the latest information and plug the formulas into a Google Sheet calculator. I should have taken better notes but I didn't realize we were going to lose the forum. Let's not lose this one too, my mind is getting old and it isn't what it used to be. Anyway, technically it should be called a Caliper/Rotor Brake Torque Bias Calculator or something.

[Johnvu]

What are the piston sizes and pad dimensions? I'll update the brake bias calculator for us.

Weight vs. heat dissipation: I'd take the unsprung weight savings of a monoblock aluminum caliper all day. If you need a 380/370 you're pretty hardcore on the track side of this debate and are not doing an F8X retrofit anyway. Agree the 996 is a lot of work for a 345 and it's a shame, but the 996 retrofit to me is about handling, pedal feel, and bling. The downfall of the 996 retrofit is the non-existing rotor selection...you're stuck with fake 2pc rotors made out of butter. Okay I'll climb down now, sorry. Whoever had bad pedal feel with the 996 needs to keep bleeding lol.

Good write-up OP.

Lol yeah, I can't personally speak to the pedal feel of the 996 swap but this pedal definitely feels pretty good. I honestly won't be anywhere near the limit for these brakes or the 996 brakes at the track since im still a noob, but they sure do look fantastic behind the wheels lol. I also figured I would have enough brakes for a long time as I learn and grow on the track =).

Also thank you for calculating the brake bias! I was starting to do the calca but then got swamped with work. Could you possibly do this for both the mk60 and DSC3?? Thanks!

[r4dr]

Any fitment advice on this kit? Do you need 19s or will 18 et35 or et22 fit them?

Based on the info in the DIY, I would expect fitment advice for the F8X to translate pretty directly to F8X brakes on the E46. I know 18" EC-7s fit from personal experience with an F82. Shaving the front caliper mounting points would move the caliper 2.5-3 mm further outboard which would affect the clearance as well.

This set up is a little more rear-biased than stock and full 996 but not bad. Updating the configuration part of the calculator so that it's easier to update in the future. Be back soon.

Is that based on Mk 60 brake bias?

[clawhamm3r]

I thought the 996 retrofit used OE rotor sizes. Is the issue that there aren't any quality two piece rotors available?

Yeah, uses the CSL/ZCP/Z4M 345mm front rotor and stock rear...and there's no aftermarket.

Pistons - 40/40mm front, 44mm rear.
Pads - (not 100% on the pad width)

Thanks, looked up replacement pistons on Racing Brake and saw the same. Got the pads from Performance Friction. This set up is a little more rear-biased than stock and full 996 but not bad. Updating the configuration part of the calculator so that it's easier to update in the future. Be back soon.

[SWRT_M3]

What are the piston sizes and pad dimensions? I'll update the brake bias calculator for us.

Weight vs. heat dissipation: I'd take the unsprung weight savings of a monoblock aluminum caliper all day. If you need a 380/370 you're pretty hardcore on the track side of this debate and are not doing an F8X retrofit anyway. Agree the 996 is a lot of work for a 345 and it's a shame, but the 996 retrofit to me is about handling, pedal feel, and bling. The downfall of the 996 retrofit is the non-existing rotor selection...you're stuck with fake 2pc rotors made out of butter. Okay I'll climb down now, sorry. Whoever had bad pedal feel with the 996 needs to keep bleeding lol.

Good write-up OP.

Pistons - 40/40mm front, 44mm rear.
Pads - (not 100% on the pad width)

[eacmen]

What are the piston sizes and pad dimensions? I'll update the brake bias calculator for us.

Weight vs. heat dissipation: I'd take the unsprung weight savings of a monoblock aluminum caliper all day. If you need a 380/370 you're pretty hardcore on the track side of this debate and are not doing an F8X retrofit anyway. Agree the 996 is a lot of work for a 345 and it's a shame, but the 996 retrofit to me is about handling, pedal feel, and bling. The downfall of the 996 retrofit is the non-existing rotor selection...you're stuck with fake 2pc rotors made out of butter. Okay I'll climb down now, sorry. Whoever had bad pedal feel with the 996 needs to keep bleeding lol.

Good write-up OP.

I thought the 996 retrofit used OE rotor sizes. Is the issue that there aren't any quality two piece rotors available?

I'll likely go with either the F8X or the 996 calipers in the future. I think 380/370 is overkill for e46, but can never have too much brakes i guess...

[clawhamm3r]

What are the piston sizes and pad dimensions? I'll update the brake bias calculator for us.

Weight vs. heat dissipation: I'd take the unsprung weight savings of a monoblock aluminum caliper all day. If you need a 380/370 you're pretty hardcore on the track side of this debate and are not doing an F8X retrofit anyway. Agree the 996 is a lot of work for a 345 and it's a shame, but the 996 retrofit to me is about handling, pedal feel, and bling. The downfall of the 996 retrofit is the non-existing rotor selection...you're stuck with fake 2pc rotors made out of butter. Okay I'll climb down now, sorry. Whoever had bad pedal feel with the 996 needs to keep bleeding lol.

Good write-up OP.

[Obioban]

the oe wheels on the F80 M3 are

18 x 9 et29
18 x 10 et40

whats the width of your 18s?

That’s not enough information to paint a complete picture— spoke design is a huge factor for bbk clearance.

[eacmen]

the oe wheels on the F80 M3 are

18 x 9 et29
18 x 10 et40

whats the width of your 18s?

9.5 square. Two sets of et35 one set et22. I assume the rears would fit.

[SWRT_M3]

Any fitment advice on this kit? Do you need 19s or will 18 et35 or et22 fit them?

the oe wheels on the F80 M3 are

18 x 9 et29
18 x 10 et40

whats the width of your 18s?

[eacmen]

Any fitment advice on this kit? Do you need 19s or will 18 et35 or et22 fit them?

[r4dr]

If you're tracking the car it's 100% worth it, otherwise they just look cool and aren't drilled which I like (which could also be worth it ). I've put them on an M4 so far and they have been incredible in terms of heat management and wear, and they will be going on a GT350 when the factory rotors are toast. Or cracked more likely, since they're drilled. I never thought I would be pimping $600/ea rotors as anything other than a waste of money but they're the real deal.

Once the M3 has its original 17-year old brake parts due for replacement, I think I'll be shopping around for an F80 set. So thanks for the DIY, it'll come in handy.

[Johnvu]

Comparing weights without acknowledging the massive increase of rotor area is missing a huge part of the upgrade... the 996 upgrade is a lot of work only to just use stock ZCP-sized rotors. Going from 345mm diameter front rotors to 380mm (the F80 rotors) alone is a 20% increase in rotor area, not to mention pad size (no idea how this compares).

I'd pair these calipers with Girodisc 2-piece rotors (https://www.girodisc.com/Rotors_c_1592.html) if I were aiming to track this setup. Those F80 rotors are boat anchors.

Yeah, I completely agree here. The main benefit of this kit is the massive increase in rotor surface area, resulting in much better heat dissipation. The weight can be offset by getting some Forged wheels that will be be about at minimum 5 lbs lighter per corner, so 20 lbs total. This will bring me to about the same weight as the 996 swap. Both are good options, but I am definitely happy with this route .

I am looking forward to getting some new rotors in the future. I will probably follow your lead and get some of those bad ass girodisc rotors. Thanks for showing me these!

[r4dr]

If anyone's feeling adventurous and wants to stuff some brakes behind those wheels: https://f80.bimmerpost.com/forums/sh....php?t=1731891

Would probably fit similarly no?

[r4dr]

Comparing weights without acknowledging the massive increase of rotor area is missing a huge part of the upgrade... the 996 upgrade is a lot of work only to just use stock ZCP-sized rotors. Going from 345mm diameter front rotors to 380mm (the F80 rotors) alone is a 20% increase in rotor area, not to mention pad size (no idea how this compares).

I'd pair these calipers with Girodisc 2-piece rotors (https://www.girodisc.com/Rotors_c_1592.html) if I were aiming to track this setup. Those F80 rotors are boat anchors.