Affordable rear brake solution for M4/M3

m4forum · 06-02-2021, 10:04 PM

I have been looking for a rear brake solution on my M4 since last year when I tracked it for the first time. As most of you know rear brakes can get really hot even on the same level as the front brakes. I had temperature stickers on my calipers which shows front/rear were around 370/380F what is really hot. I would understand the front getting hot but not the rear. Later found out about the MDM but even after disabling it still didnt resolve the issue. In summary the brakes are NOT up to the task if you push it hard, R compound, track and drive skills.

What I have tried : brake cooling with duct, different pads, turn off MDM. Nothing resolved the problem.

I could not believe a BBK was required for rear also. For the front I get it. For the rear I dont get it.

After some deep dive I realized (as already shared on this community) that M2C/CCB rear brakes are a great alternative at a reasonable cost I just didn't know how good the solution would be. This weekend I was able to test at Mid Ohio and the results could not be better, I was really surprised.

As I didnt want to take any chances decided to use all the options to lower the temperatures so my final solution was : gold CCB calipers (4 pistons 28mm diam), Girodisc 380x28mm and SS pistons. I am using PFC 01 pads. Also installed an active cooling fan (see pictures).

How I tested it. Just drove as hard as I could for the full 30 min for all sections with EURO MDM ON. In total I got ~ 100 laps with a best lap on club layout 1:39.4 what is pretty good for this car. I am using Toyo RR tires.

Results : my temperature dropped from 370F to 300F and pad wear is minimal. You can see that driver side was a little bit hotter than passenger as it is a clockwise track. All my testing was with fan on. But for one section only (30 min) I turned off the fan in order to stress the brakes as much as possible when I noticed the first square on temperature stripe turned black showing the fans are definitely helping to manage the temperature. Last but not least I also paint the rotor vanes with Genesis brake temperature paint as I wanted to assure was not over cooling the system. I was able to confirm rotor temp around 1000F what is pretty good.

Was also very curious to know about brake bias. Solo DL has front and rear brake pressure so I was able to calculate brake torque and bias which is around 60-65% (see below).

[IMG]

[/IMG]

I spent around $2,700 for a solution that is extremely capable and certainly can satisfy most of the drivers out there. You can save $700 by going with stock OEM 380x28mm rotors based on tires, skills and track you drive.

My next test will be Watkins Glen which is harder on brakes but I am convinced based on the results I got it will perform very well.

[IMG]

[/IMG]

[IMG]

[/IMG]

FaRKle! · 06-03-2021, 01:54 AM

FWIW the 350hp variant of the M2 CS Racing the M2C rear brake setup too. The 450hp variant gets the Alcon rear BBK though (although it's a smaller diameter rotor but thicker).

m4forum · 06-03-2021, 07:22 AM

Thanks for sharing. The original M2C rear brakes uses the same caliper I have (just different color) but has BMW OEM rotor with have the same dimensions as girodisc but 30-32 vanes. On my case I have 48 vanes with girodisc, better material and stainless steel which helps to lower fluid temperature. I am pretty use the Alcon BBK you mentioned had better rotor and piston which will definitely improves its thermal performance.

melanthius · 06-03-2021, 11:59 PM

I love the dedication! (obsession?)

What is your suspension and wheel/tire setup?

m4forum · 06-04-2021, 07:56 AM

I am using Ohlins R/T and Toyo RR

stevehifi · 06-06-2021, 02:40 AM

How did you end up with $2700? The giro discs (front and back) alone are $2500. Then you have to buy the gold/red calipers which is another 3500 or so, then pads..

at that price point might as well shell out for a stoptech trophy or go up the AP racing.

m4forum · 06-06-2021, 09:05 AM

$2,700 is only for the rear. Could have done the front and I believe would be substantial better than blue calipers due thickness and 6 piston. The reason I didnt do the front is because I would like to stay with 18" tires. Maybe few years from now 19" tire R compound with have same availability as 18".
Still much cheaper than any BBK. As I said you can go cheaper with stock rotors but on my case I was looking to optimize performance as much as possible.
Other advantage is the possibility to use MDM w/o extreme temperatures.

melanthius · 06-08-2021, 02:13 PM

Quote:

Originally Posted by m4forum

I am using Ohlins R/T and Toyo RR

How much harder / hotter would you think the brakes are working on 40TW tire compared to 100TW?

m4forum · 06-08-2021, 03:55 PM

it all depends on grip level you have but some 100TW can generate above 1.0g grip level what I see as already high for stock brakes. Best way is to put some temperature stickers and see temperature level you are getting.

melanthius · 06-09-2021, 12:22 AM

Quote:

Originally Posted by m4forum

it all depends on grip level you have but some 100TW can generate above 1.0g grip level what I see as already high for stock brakes. Best way is to put some temperature stickers and see temperature level you are getting.

call me dumb, but I'm looking at your temperature sticker photos and I am not sure if I am reading them correctly. I see one that's solid orange, another that's solid silver, and the last one is all orange except for one box.

Help me out here?

m4forum · 06-09-2021, 08:02 AM

when a temperature is achieved the box turn black. On this case there is only one sticker that reaches this condition showing the calipers were running at "low" temperature.
Driver : outside reaches 300F / inside below 270F
Passenger : outside below 300F / inside below 270F

Considering both sides before the upgrade were running 370F on outside is a huge improvement AND with MDM on.

06-02-2021, 10:04 PM	#1
m4forum First Lieutenant 76 Rep 344 Posts Drives: M3 Join Date: Oct 2015 Location: Michigan iTrader: (6)	Affordable rear brake solution for M4/M3 I have been looking for a rear brake solution on my M4 since last year when I tracked it for the first time. As most of you know rear brakes can get really hot even on the same level as the front brakes. I had temperature stickers on my calipers which shows front/rear were around 370/380F what is really hot. I would understand the front getting hot but not the rear. Later found out about the MDM but even after disabling it still didnt resolve the issue. In summary the brakes are NOT up to the task if you push it hard, R compound, track and drive skills. What I have tried : brake cooling with duct, different pads, turn off MDM. Nothing resolved the problem. I could not believe a BBK was required for rear also. For the front I get it. For the rear I dont get it. After some deep dive I realized (as already shared on this community) that M2C/CCB rear brakes are a great alternative at a reasonable cost I just didn't know how good the solution would be. This weekend I was able to test at Mid Ohio and the results could not be better, I was really surprised. As I didnt want to take any chances decided to use all the options to lower the temperatures so my final solution was : gold CCB calipers (4 pistons 28mm diam), Girodisc 380x28mm and SS pistons. I am using PFC 01 pads. Also installed an active cooling fan (see pictures). How I tested it. Just drove as hard as I could for the full 30 min for all sections with EURO MDM ON. In total I got ~ 100 laps with a best lap on club layout 1:39.4 what is pretty good for this car. I am using Toyo RR tires. Results : my temperature dropped from 370F to 300F and pad wear is minimal. You can see that driver side was a little bit hotter than passenger as it is a clockwise track. All my testing was with fan on. But for one section only (30 min) I turned off the fan in order to stress the brakes as much as possible when I noticed the first square on temperature stripe turned black showing the fans are definitely helping to manage the temperature. Last but not least I also paint the rotor vanes with Genesis brake temperature paint as I wanted to assure was not over cooling the system. I was able to confirm rotor temp around 1000F what is pretty good. Was also very curious to know about brake bias. Solo DL has front and rear brake pressure so I was able to calculate brake torque and bias which is around 60-65% (see below). [IMG][/IMG] I spent around $2,700 for a solution that is extremely capable and certainly can satisfy most of the drivers out there. You can save $700 by going with stock OEM 380x28mm rotors based on tires, skills and track you drive. My next test will be Watkins Glen which is harder on brakes but I am convinced based on the results I got it will perform very well. [IMG][/IMG] [IMG][/IMG] [IMG][/IMG] [IMG][/IMG] [IMG][/IMG] [IMG][/IMG]
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06-03-2021, 01:54 AM	#2
FaRKle! Brigadier General 4007 Rep 3,535 Posts Drives: 328d Wagon, M2 Comp, i4 eD35 Join Date: Sep 2016 Location: Bay Area, CA iTrader: (4) Garage List 2023 BMW i4 eDrive 35 [0.00] 2017 BMW 328dx Wagon [0.00] 2021 BMW M2 Competi ... [0.00]	FWIW the 350hp variant of the M2 CS Racing the M2C rear brake setup too. The 450hp variant gets the Alcon rear BBK though (although it's a smaller diameter rotor but thicker).
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06-03-2021, 07:22 AM	#3
m4forum First Lieutenant 76 Rep 344 Posts Drives: M3 Join Date: Oct 2015 Location: Michigan iTrader: (6)	Thanks for sharing. The original M2C rear brakes uses the same caliper I have (just different color) but has BMW OEM rotor with have the same dimensions as girodisc but 30-32 vanes. On my case I have 48 vanes with girodisc, better material and stainless steel which helps to lower fluid temperature. I am pretty use the Alcon BBK you mentioned had better rotor and piston which will definitely improves its thermal performance.
	Appreciate 0 Quote

06-03-2021, 11:59 PM	#4
melanthius Second Lieutenant 255 Rep 295 Posts Drives: 2015 M3 Join Date: May 2018 Location: SF Bay Area, CA iTrader: (0)	I love the dedication! (obsession?) What is your suspension and wheel/tire setup?
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06-04-2021, 07:56 AM	#5
m4forum First Lieutenant 76 Rep 344 Posts Drives: M3 Join Date: Oct 2015 Location: Michigan iTrader: (6)	I am using Ohlins R/T and Toyo RR
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06-06-2021, 02:40 AM	#6
stevehifi Captain 527 Rep 855 Posts Drives: 17 F80 M3 ZCP Join Date: May 2008 Location: Irvine,CA iTrader: (5)	How did you end up with $2700? The giro discs (front and back) alone are $2500. Then you have to buy the gold/red calipers which is another 3500 or so, then pads.. at that price point might as well shell out for a stoptech trophy or go up the AP racing.
	Appreciate 0 Quote

06-06-2021, 09:05 AM	#7
m4forum First Lieutenant 76 Rep 344 Posts Drives: M3 Join Date: Oct 2015 Location: Michigan iTrader: (6)	$2,700 is only for the rear. Could have done the front and I believe would be substantial better than blue calipers due thickness and 6 piston. The reason I didnt do the front is because I would like to stay with 18" tires. Maybe few years from now 19" tire R compound with have same availability as 18". Still much cheaper than any BBK. As I said you can go cheaper with stock rotors but on my case I was looking to optimize performance as much as possible. Other advantage is the possibility to use MDM w/o extreme temperatures.
	Appreciate 0 Quote

06-08-2021, 03:55 PM	#9
m4forum First Lieutenant 76 Rep 344 Posts Drives: M3 Join Date: Oct 2015 Location: Michigan iTrader: (6)	it all depends on grip level you have but some 100TW can generate above 1.0g grip level what I see as already high for stock brakes. Best way is to put some temperature stickers and see temperature level you are getting.
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06-09-2021, 08:02 AM	#11
m4forum First Lieutenant 76 Rep 344 Posts Drives: M3 Join Date: Oct 2015 Location: Michigan iTrader: (6)	when a temperature is achieved the box turn black. On this case there is only one sticker that reaches this condition showing the calipers were running at "low" temperature. Driver : outside reaches 300F / inside below 270F Passenger : outside below 300F / inside below 270F Considering both sides before the upgrade were running 370F on outside is a huge improvement AND with MDM on.
	Appreciate 0 Quote