F80 M3 / F82 M4 Brake Caliper/Rotor Retrofit Guide to E9x M3 - Using OEM Parts

[gmx]

Originally Posted by tdott

It's on page 2.
https://www.m3post.com/forums/showpo...8&postcount=32

I wonder if anyone doing this also checked their track widths and ofc camber/caster with the standard upright part numbers.

I heard from someone else they gained -0.5 NOT using the F8x camber correction parts. Can anyone please confirm... Just get it on the rack and see where you max out compared to before.

I'm skeptical of the measurement taken on pp2 around the angle of the strut into the bearing relative to the hub face. Something is wrong here.

[maddmatth]

Originally Posted by gmx

I wonder if anyone doing this also checked their track widths and ofc camber/caster with the standard upright part numbers.

I heard from someone else they gained -0.5 NOT using the F8x camber correction parts. Can anyone please confirm... Just get it on the rack and see where you max out compared to before.

I'm skeptical of the measurement taken on pp2 around the angle of the strut into the bearing relative to the hub face. Something is wrong here.

I don't get why you guys are going with the F80 spindles when a working adapter exists? It's cheaper and doesn't affect suspension geometry.

https://epytec.de/en/bmw-3er-e92-e93...0-4-piston-694

I found a mechanic in Melbourne that installed it successfully on a customer's car. So I'm going to use it for mine.

[tdott]

Originally Posted by maddmatth

I don't get why you guys are going with the F80 spindles when a working adapter exists? It's cheaper and doesn't affect suspension geometry.

https://epytec.de/en/bmw-3er-e92-e93...0-4-piston-694

I found a mechanic in Melbourne that installed it successfully on a customer's car. So I'm going to use it for mine.

Rather trust an OEM setup over some undersized bolts. I track my car hard, don't need to be worrying about brakes.

It also wasn't available when this thread was first started.

If you guys think this hardware is beefy enough for brakes esp hard use on track, go right ahead, take the cheap way out when there is a proven OEM solution where there is no doubts about safety.

[gmx]

Originally Posted by maddmatth

I don't get why you guys are going with the F80 spindles when a working adapter exists? It's cheaper and doesn't affect suspension geometry.

https://epytec.de/en/bmw-3er-e92-e93...0-4-piston-694

I found a mechanic in Melbourne that installed it successfully on a customer's car. So I'm going to use it for mine.

Camber gains reportedly. Some are gaining track width and camber in addition to a height change
That's what I'm asking and if that's true, the strut angle on pp2 makes no sense or the face where the wheel bearing sits has not been measured/compared sufficiently. I don't have F8x brakes anyway, personally I believe they're a downgrade from E9x but nice for aesthetics.
I got F8x spindles, if your mech or anyone you know has E9x M ones sitting around let me know and I know someone in Melb that can probably get them scanned to get this shit done/confirmed or not.

[tdott]

Originally Posted by gmx

Camber gains reportedly. Some are gaining track width and camber in addition to a height change
That's what I'm asking and if that's true, the strut angle on pp2 makes no sense or the face where the wheel bearing sits has not been measured/compared sufficiently. I don't have F8x brakes anyway, personally I believe they're a downgrade from E9x but nice for aesthetics.
I got F8x spindles, if your mech or anyone you know has E9x M ones sitting around let me know and I know someone in Melb that can probably get them scanned to get this shit done/confirmed or not.

My height, camber and caster are adjustable, so I was able to get the car where I needed it to be, that's about all I could tell you.

I track my car a lot and I am happy with the upgrade for the price I paid for my setup before prices went up. Track pad availability is also great. So not really sure where you are getting your downgrade information from.

[gmx]

Yeah but can you max out camber more or not? Once you bolted it all up, did your camber skyrocket and you had to pull out some from the top plate (or lower arm in?).
Next time you go for an alignment, shove the strut all the way in and see what you get. If anyone can get close to or at -4 at pretty standard ride heights, then there's a good reason to believe brakes aren't the only "gain".

As for the brakes, the total piston diameter is smaller. And the front pads are a bit small hence why they wear pretty quick esp compared to a bigger pad that APs/Brembo etc take. But yes, they look nice and aren't an inferior slider caliper.

[maddmatth]

Originally Posted by gmx

I don't have F8x brakes anyway, personally I believe they're a downgrade from E9x but nice for aesthetics.

Err... a downgrade how??? F8x brakes are widely considered a significant upgrade over E9x. 4/2 piston calipers instead of single piston sliding calipers and they're larger.

Originally Posted by tdott

Rather trust an OEM setup over some undersized bolts. I track my car hard, don't need to be worrying about brakes.

It also wasn't available when this thread was first started.

If you guys think this hardware is beefy enough for brakes esp hard use on track, go right ahead, take the cheap way out when there is a proven OEM solution where there is no doubts about safety.

Why do you think the bolts are an issue? The mechanics I've spoken to didn't see an issue with it, and they deal a lot with track and race cars too. It's made by a German company and their stuff is TUV approved, and TUV are known to be pretty stringent as far as I know.

If you've got a good reason for thinking these are unsafe then I'll reconsider them for myself, I plan to use my car for trackdays so I don't want to take stupid risks either.

[M3SQRD]

Originally Posted by maddmatth

Err... a downgrade how??? F8x brakes are widely considered a significant upgrade over E9x. 4/2 piston calipers instead of single piston sliding calipers and they're larger.

The e9x M front and rear single-piston sliding calipers have 12% and 9%, respectively, more piston area than the f8x blue 4-piston fixed front and 2-piston fixed rear calipers.

A larger OD rotor doesn’t always mean it produces more brake torque than a smaller OD rotor. The f8x front rotor OD is 14.96” and the pad radial depth (PRD) is 2.576”. Brake torque is based on the mean radius of the brake rotor which is:

Rmean_f8xf = Rotor OD / 2 - PRD / 2 = 14.96/2 - 2.576/2 = 6.192”

The e9x M rotor OD is 14.567” and PRD is 2.244” so

Rmean_e92f = 14.567/2 - 2.244/2 = 6.161”

So the f8x front rotor has a larger mean radius of 31 mil than the mean radius of the e9x M front rotor even though the f8x front rotor OR is 197 mil larger than the e9x M rotor OR.

Similarly, for the rear, the f8x rear rotor OD is 14.567 and PRD is 2.480” so

Rmean_f8xr = 14.567/2 - 2.480/2 = 6.044”

E9x M rear rotor OD is 14.273” and PRD is 2.047” so

Rmean_e9xr = 14.273/2 - 2.047/2 = 6.113”

The e9x M rear rotor actually has a larger mean radius of 69 mil than the 197 mil physically larger f8x rear rotor OR.

Interestingly, the f8x blue brake setup and e9x M brake setup have the same forward brake bias of 0.63 but has a slightly lower brake torque output front and rear with the f8x blue brake setup. With the physically smaller piston areas of the f8x blue calipers, the e9x M brake pedal with the f8x blue brake setup should feel slightly stiffer and have a slightly shorter pedal travel than the e9x M stock brake setup. Consequently, the f8x blue brake setup is not an upgrade in braking performance (when grippier tires are used) but it does improve the thermal mass and cooling compared to the stock e9x brake setup.

[maddmatth]

Originally Posted by M3SQRD

Consequently, the f8x blue brake setup is not an upgrade in braking performance (when grippier tires are used) but it does improve the thermal mass and cooling compared to the stock e9x brake setup.

Ok but who is just measuring performance in brake torque? If that was our main performance measure we'd be fine with 318i brakes lol. You'll still have enough capability to stop from any speed and achieve max braking force - once

The thermal mass and cooling is exactly why it's an upgrade - and perhaps the 4 / 2 piston design gives a more precise feel over the sliding calipers.

Is the small loss in torque a problem?

[M3SQRD]

Originally Posted by maddmatth

Ok but who is just measuring performance in brake torque? If that was our main performance measure we'd be fine with 318i brakes lol. You'll still have enough capability to stop from any speed and achieve max braking force - once

The thermal mass and cooling is exactly why it's an upgrade - and perhaps the 4 / 2 piston design gives a more precise feel over the sliding calipers.

Is the small loss in torque a problem?

The point I was trying to make is there’s actually a loss of applied torque relative to the e9x M stock brakes even though there’s an increase in rotor diameter with the f8x blue brake setup. Larger rotors and more pistons in a caliper by themselves doesn’t mean there’s an increase in braking torque so this is a case where a “big brake” setup actually netted a tiny loss of brake torque. You asked about it being a “downgrade” so comparing quantitative braking metrics between the two setups, the net losses of piston area and brake torque, the f8x blue brake setup is effectively a downgrade relative to the stock setup except for the increase in thermal mass and slightly improved cooling (f8x rotors are less restrictive around the entrance to the cooling vanes due to material cutouts in the aluminum hat). Does that mean it’s a problem? No. I have not driven an e9x M with the f8x blue setup so I can’t compare brake pedal feel relative to my f8x (I no longer run the blue brake setup).

[maddmatth]

Originally Posted by M3SQRD

The point I was trying to make is there’s actually a loss of applied torque relative to the e9x M stock brakes even though there’s an increase in rotor diameter with the f8x blue brake setup. Larger rotors and more pistons in a caliper by themselves doesn’t mean there’s an increase in braking torque so this is a case where a “big brake” setup actually netted a tiny loss of brake torque. You asked about it being a “downgrade” so comparing quantitative braking metrics between the two setups, the net losses of piston area and brake torque, the f8x blue brake setup is effectively a downgrade relative to the stock setup except for the increase in thermal mass and slightly improved cooling (f8x rotors are less restrictive around the entrance to the cooling vanes due to material cutouts in the aluminum hat). Does that mean it’s a problem? No. I have not driven an e9x M with the f8x blue setup so I can’t compare brake pedal feel relative to my f8x (I no longer run the blue brake setup).

So the loss in torque isn't established to result in any actual loss in performance.
You're calling it a downgrade over something inconsequential and dismissing the actual improvement that people are seeking out when they get bigger brakes.

It's just silly logic.

[M3SQRD]

Originally Posted by maddmatth

So the loss in torque isn't established to result in any actual loss in performance.
You're calling it a downgrade over something inconsequential and dismissing the actual improvement that people are seeking out when they get bigger brakes.

It's just silly logic.

So before I did the calculations, I bet you had assumed the f8x blue larger diameter rotors and multi-piston fixed calipers produced more brake torque, not less or equal? Bigger isn’t always better. I wouldn’t call the f87C 2NH brake kit better because it adds something like 40 lbm of unsprung weight.

The primary reasons for a brake kit are increased thermal capacity and cooling. An additional primary reason for a “big” brake kit is also increased torque capability or at least that’s a selling point.

[tdott]

Originally Posted by M3SQRD

Consequently, the f8x blue brake setup is not an upgrade in braking performance (when grippier tires are used) but it does improve the thermal mass and cooling compared to the stock e9x brake setup.

So slightly stiffer pedal, slightly more rear bias. IMO both are small and more rear bias is actually preferred to keep the rear stable under heavy braking, heavy braking is much more stable at the track compared to stock which had the car dancing around.

Sounds like you are nit picking the small differences and understating the major benefits (fixed caliper, larger rotors/better cooling). The main issue with stock brakes at the track is instability, and cooling. Both of which are addressed and a definite upgrade.

Is it as good as a beefy bbk? No. Is it an upgrade over stock. Definitely Yes.

[tdott]

Originally Posted by gmx

Next time you go for an alignment, shove the strut all the way in and see what you get. If anyone can get close to or at -4 at pretty standard ride heights, then there's a good reason to believe brakes aren't the only "gain".

I don't care about max camber, as long as I can adjust it to what I need.

It does have added camber, which is usually want everyone wants, removing pins, etc. So even on a stock-ish car more camber is desired and it isn't enough to be a concern. The height increase is known and everyone is using lowering spring or height adjustable suspension, so not really a concern.

[M3SQRD]

Originally Posted by tdott

So slightly stiffer pedal, slightly more rear bias. IMO both are small and more rear bias is actually preferred to keep the rear stable under heavy braking, heavy braking is much more stable at the track compared to stock which had the car dancing around.

Sounds like you are nit picking the small differences and understating the major benefits (fixed caliper, larger rotors/better cooling). The main issue with stock brakes at the track is instability, and cooling. Both of which are addressed and a definite upgrade.

Is it as good as a beefy bbk? No. Is it an upgrade over stock. Definitely Yes.

All I did was compare the primary metrics of the stock brake setup to the f8x brake setup. I’m certain everyone running the f8x setup believed it had a higher brake torque output front and rear relative to the e9x M stock setup. That’s not the case. The brake bias remains the same because the f8x blue brakes have lower torque output front and rear. Did I say don’t switch to the f8x blue setup? No. Did I say it was an inferior setup to the e9x M stock brakes? No. Objectively, f8x blue setup relative to the stock setup has (1) less piston area, (2) lower torque output, (3) firmer pedal, (4) improved thermal mass and (5) improved cooling. All true and if you assigned “+” and “-“ for each metric it would be “-“, “-“, “- or +“, “+” and “+”. I had the f8x blue setup on my f82 so I know how it performs on track and what its limitations are. I no longer run the f8x blue brake setup.

[tdott]

Originally Posted by M3SQRD

All I did was compare the primary metrics of the stock brake setup to the f8x brake setup.

You also responded in support of GMX claim of it being a downgrade, my response was directed more towards that statement and not towards you in particular.

Originally Posted by M3SQRD

I’m certain everyone running the f8x setup believed it had a higher brake torque output front and rear relative to the e9x M stock setup.

I'm not sure that is true, Total effective brake torque being slightly less doesn't mean much as both will lock up the brakes, the on track endurance and cooling performance improvement is the main draw imo. (aesthetic to a lesser extent to some)

Expecting a higher brake torque from a bbk is flawed thinking, and should not be the reason someone chooses to upgrade.

Originally Posted by M3SQRD

That’s not the case. The brake bias remains the same because the f8x blue brakes have lower torque output front and rear.

There is a 1% difference in brake bias at the piston.

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 - Stock bias 62%

Also keep in mind these are simplified calculations, not taking into account all variables. Mainly just good for comparison on paper.

IMO it doesn't take into account 4 piston vs 1 single piston sliding caliper, friction on the sliding caliper reduces clamping force compared to a multi piston fixed caliper and isn't taking into account.

[M3SQRD]

Originally Posted by tdott

You also responded in support of GMX claim of it being a downgrade, my response was directed more towards that statement and not towards you in particular.



I'm not sure certain that is true, Total effective brake torque doesn't mean much as both will lock up the brakes, the on track endurance and cooling performance is the main draw imo.



There is a 1% difference in brake bias.

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%

I get a 0.2% difference in forward bias - 63% vs. 62.8%. What are the pad radial depths (PRDs) you’re using? Brake bias isn’t calculated using only the caliper piston area. The brake rotor mean radius (OR - PRD/2) is required to convert caliper clamping force into applied brake torque. Brake torque output does make a difference with proper tires, spring rates and damper settings which allows you to go deeper into a brake zone with an improvement in initial deceleration…because the calculated dynamic brake bias is around ~70-72% forward which is more important than static brake bias. To combat this, I run a rear pad with a higher CoF than the front to bring the dynamic brake bias back into the mid-high 60% range.

[gmx]

Disappointed at the lack of technical depth and detail into potential geometry gains.
By moving the wheel bearing up and correcting the "height", you're now risking lowering the LCA outer pivot above the inner and who knows dynamically if the curves; toe/camber are different. That's where there are real complimentary potential gains as opposed to crap like unsealed bump correction arms/end links or $$ parts such as GTS/Strom uprights.

[tdott]

Originally Posted by gmx

Disappointed at the lack of technical depth and detail into potential geometry gains.

Feel free to go ahead and do your own measurements then. Not sure what you are expecting here? Someone else to do the work to answer questions to satisfy your own curiosity? These are advanced concepts, the average person does not have the tools to precisely measure any of that.

Moving the wheel bearing up, pushes the lower control arm down, when lowering the car from it's stock position, LCA will be in a better/closer to stock static position than a stock knuckle lowered car.

You sound more like a stock suspension guy thinking every mm change from stock will make the car fail. You don't like it, go back to stock, no one is forcing you to keep it.

[regbf99]

Originally Posted by Turbz

Hi I was looking to do this brake upgrade on my e93 335i. I have fitted the front 380mm rota using the adapter bracket from seems legit garage and now want to do the rears and wanted to ask if anyone would know if the complete m3 rear knuckle assembly would fit the 335i so I can just use spacers like you guys are doing. Thank you

I would also like to do this conversion on my 335i.
The problem with the ABS sensor should be dealt with.
But what is a much bigger obstacle is the clamping of the shock absorber.
On the M3 there is a sleeve/cone on the shock absorber, on the non-M this area is cylindrical.
So the conversion would only work if the M3's dampers were also installed.
Can anyone confirm this or do you have any other information?

[M3SQRD]

Originally Posted by regbf99

I would also like to do this conversion on my 335i.
The problem with the ABS sensor should be dealt with.
But what is a much bigger obstacle is the clamping of the shock absorber.
On the M3 there is a sleeve/cone on the shock absorber, on the non-M this area is cylindrical.
So the conversion would only work if the M3's dampers were also installed.
Can anyone confirm this or do you have any other information?

Are you asking about using a f8x knuckle with e9x non-M dampers? If you are then the answer is no because the e9x M and f8x both have a larger diameter where the strut engages the f8x knuckle. You need to run all f8x - f8x knuckle, f8x front strut, and f8x brake calipers and rotors. E9x non-M struts will not work.

[regbf99]

Thanks for the confirmation, that's how I see it too.
I already have f8x brake calipers, but together with the f3x brake discs (370mm).
Let's see if I can install the f8x calipers together with e92 M3 struds.
The coupling rods would also have to be adjusted, as they are different from the 335i to the M3.
Has anyone taken a closer look at the ABS sensors off the non-M in combination with the f8x knuckle?