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      06-17-2020, 02:01 AM   #1
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Why cheap rear brake calipers on M5 (and M8)?

I just concluded brake upgrade on my M3E92, installed M4F8x set (more here: https://www.expressivedrives.com/blog/f8x-brakes-to-f9x).

Then I noticed, that even the F90 M5 and F9x M8 have low tech and heavy cast iron floaters in rear.



It made me wonder why they don't use something more attractive and technologically advanced from their part shelf - some two or four cylinder alloy calipers? Is it because of bean counters, saving few hundred $$$ or is there a design reason?
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      06-17-2020, 03:14 AM   #2
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It could be a brake bias distribution aspect of their engineering. Maybe the cars are front heavy vs. the F8x where it’s more 50/50
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      06-17-2020, 03:16 AM   #3
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Electric handbrake thing. Have a close look at the rear discs on a high end mid-rear car such as a Ferrari or McLaren and you'll see they have 2 calipers or they'll have a weird section at the top of the caliper.

That's why the F80 is 'normal'

For our 51-53% front weight cars the rear caliper doesn't really matter
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      06-17-2020, 03:29 AM   #4
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it saves money.
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      06-17-2020, 04:15 AM   #5
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It´s because of the integrated parking brake as brad850csi mentioned. On M3/M4 it was standard manual handbrake, but with the electronic handbrake you need to have more robust rear caliper as I understood.
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      06-17-2020, 04:56 AM   #6
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Because the rear doesn’t contribute so much braking on a typical front heavier car. When the weight shifts forward the front accounts for more than 70% of brake torque. The unloaded rear doesn’t (and can’t) develop a lot of deceleration. So money is best invested into the front brakes.

Last edited by 5.M0NSTER; 06-17-2020 at 05:04 AM..
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      06-17-2020, 08:18 PM   #7
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if AMG can do it, M can do it. zero excuse for this nonsense. Seriously. M5's and m8's are well into 100k range, inexcusable.
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      06-23-2020, 02:05 AM   #8
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Quote:
Originally Posted by TrevorM3 View Post
if AMG can do it, M can do it. zero excuse for this nonsense. Seriously. M5's and m8's are well into 100k range, inexcusable.
I agree 100%. The rear caliper on the M5 looks terrible (even with the $9000 CCB option). I was a bit disappointed when I picked up the car. Heck, our Audi S5 has nicer looking rear calipers.
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      07-11-2020, 05:05 PM   #9
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Maybe they reused the F10's rear calipers? I'm not facile enough to tell.

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      07-12-2020, 10:10 AM   #10
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Quote:
Originally Posted by TrevorM3 View Post
if AMG can do it, M can do it. zero excuse for this nonsense. Seriously. M5's and m8's are well into 100k range, inexcusable.
AMG Ceramic with EPB uses a TRW Floating Caliper as well.

It's simple, very light, and provides the proper rotor-pad heat dissipation since MCCB's do not have functioning cooling ducts.
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      07-22-2020, 09:52 AM   #11
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mercedes doesn't even put CC rotors on the rear anymore. so you get CCB on the front and steel on the rear.
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      09-02-2020, 07:00 PM   #12
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4 pots

So, in this case, is it possible to fit the nice looking calipers from M4/M3 or is it not possible due to mentioned electronic hand brake?
These are sexy of only would be possible....
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Last edited by ballofgold_M3; 09-02-2020 at 07:05 PM.. Reason: Adding picture
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      09-02-2020, 08:06 PM   #13
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mercedes does a real caliper in the rear, no reason why bmw can't. this shit keeps me up nights. 135k car, and a honda civic caliper.
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      09-03-2020, 07:13 AM   #14
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The lambo urus too have small one in the back
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      09-03-2020, 04:42 PM   #15
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Quote:
Originally Posted by TrevorM3 View Post
mercedes does a real caliper in the rear, no reason why bmw can't. this shit keeps me up nights. 135k car, and a honda civic caliper.
And most annoyingly, no options to upgrade by the looks of it.
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      09-03-2020, 04:44 PM   #16
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Quote:
Originally Posted by MTHX View Post
The lambo urus too have small one in the back
And some men have small ones, but doesn't mean it's ok
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      09-04-2020, 07:39 AM   #17
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Quote:
Originally Posted by ballofgold_M3 View Post
And some men have small ones, but doesn't mean it's ok
lol

People can change the brake setup on their m5 .... but probably difficult to change the other one.

btw, i don't stand on my rear caliper and crying ... i prefer driving my car. The braking performamce is already great on this car, and since it's a sedan, i don't really care about the design of my caliper.
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      09-05-2020, 02:07 PM   #18
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Quote:
Originally Posted by MTHX View Post
lol

People can change the brake setup on their m5 .... but probably difficult to change the other one.

btw, i don't stand on my rear caliper and crying ... i prefer driving my car. The braking performamce is already great on this car, and since it's a sedan, i don't really care about the design of my caliper.
Braking one time in a straight line is one thing. Performance brakes on a car like ours is about braking really really hard, multiple times, in a very short period of time. Multipiston and big brake systems are all about that. The rear brake on the M5 is not well suited to this. After replacing my rear pads in a 2:1 ratio over the front (almost 3:1), BMW could have just used the rear caliper from the M2 or the M4. Why use the one off grandma's 530? I don't know.

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      09-14-2020, 08:33 PM   #19
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I've been looking into this for awhile (past two years). Definitely a cost savings, but why on a six figure car? The G8X M cars are also going to a floating rear caliper.

My take is that it's cost, serviceability, and noise. Most drivers of these cars are not tolerant of any brake noise - floating calipers are easier to keep quiet and have less parts to lubricate, corrode, etc.

They won't usually see the track, so the rear compromise isn't a big deal.

Still, it's a mystery. As an enthusiast, I'd rather have a proper fixed caliper braking system at all four corners.
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      10-03-2020, 05:15 PM   #20
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Quote:
Originally Posted by gsrbri View Post
I've been looking into this for awhile (past two years). Definitely a cost savings, but why on a six figure car? The G8X M cars are also going to a floating rear caliper.

My take is that it's cost, serviceability, and noise. Most drivers of these cars are not tolerant of any brake noise - floating calipers are easier to keep quiet and have less parts to lubricate, corrode, etc.

They won't usually see the track, so the rear compromise isn't a big deal.

Still, it's a mystery. As an enthusiast, I'd rather have a proper fixed caliper braking system at all four corners.
The rear compromise is a big deal to me. The pad can't absorb enough heat and they wear too quick by comparison to the fronts.

NO REASON they couldn't put the M2's caliper back there. None.

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      10-24-2020, 02:58 PM   #21
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ARRRGGGHHHH.

One of my bestest tech buddies gives me the following:

"This 1-piston floating rear caliper has received complaints since F10 M5 replacing the original rear drum brake. Be aware for F80 M2/3/4 they still retain the rear drum brakes (more for track oriented cars) as e-PB (dual function) is only good for "Parking" and never can serve for "Emergency" braking. That's why the rear M2 4 pot calipers can't be installed on M5 because you will lose the "parking" functionality."

Well. I hadn't done a brake job on the back of an M2. So I didn't know. He did.

Dammit.

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