Pad fade normal?

[m4forum]

Hi CanAutMe thanks for sharing. I reviewed my numbers based on your observation and agree that M2C is heavier than stock (why I didnt see at the first time). Anyway the difference doesnt look that big for the rear. I weight again the items. The only one I cannot weight was stock caliper but is still in the car.

Stock brakes rear:
rotors : 19.6 lbs (used)
caliper blue (2 piston): 7.93 lbs (info from this forum / picture of scale)
pads : 1.38 lbs (new)
total : 28.91 lbs

M2C
rotors : 20.6 lbs (new)
caliper gold (4 piston): 7.00 lbs
pads : 2.42 lbs (new)
total : 30.02 lbs

M2C is heavier by only 1.11 lbs per corner for rear.

The biggest difference is for the front ~ 12.8 lbs (w/o pads) between BBK AP vs M2C.

Please let me know if you have different numbers but I agree 35 lbs delta for all 4 corners looks a little bit too much.

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[m4forum]

The comparison I am making is for rear between stock iron vs M2C iron. Difference in weight is negligible but there is a substantial improvement in performance.

For clarity the information on this link related to rear brake M2C doesnt match waht I see reported. The link below says rear brake uses 380x30 but in reality it uses 380x28. Also weight for rotors and calipers are higher than what I have.

https://f87.bimmerpost.com/forums/sh....php?t=1497066

[CanAutM3]

Originally Posted by xxaarraa

I think 35lbs is way too high of an estimate.

I weighed my girodiscs vs CCBs. Here: https://f80.bimmerpost.com/forums/sh...5&postcount=20

So, 6 pot/4 pot calipers and steel rotors are only ~46 lbs heavier than carbons. Which means they cannot be 35 lbs heavier than OE 'small' steel brakes. Otherwise, it would mean you are saying OEM 'small' steel brakes are only 10 lbs heavier than carbons, which is simply not true.

The smaller calipers and steel rotors will be lighter than M2C OEM BBK, but not that much lighter. My guess is its about a 10-15 lbs weight penalty at best. Which on a 3650 lb car, not even a pro driver is likely to notice.

I was going with the information published in this thread: https://f87.bimmerpost.com/forums/sh....php?t=1497066

However, looking at it deeper and combined with the data provided by m4forum , I came to realize that hellrotm misquoted the rear M2C big brake rotor weight. He seems to have taken the front blue rotor weight for the rear grey one.

Recalculating with the revised M2C rear rotor weight I get those difference between the systems:
18.2lb Blue vs CCB
27.5lb Blue vs Grey
45.7lb Grey vs CCB

27~28lb unsprung weight is not negligible. If one goes through the trouble and cost of replacing rotors, calipers and pads, might as well go for an aftermarket BBK IMO, and not suffer the unsprung weight penalty. In your case, where it is only a question of swapping CCB rotors for the iron ones, yes it does make sense cost wise.

For reference:

[m4forum]

I am glad information was helpful. Hopefully on next few weeks I will be able to try out my setup at Mid Ohio. Will post the results here.

[USSEnterprise]

Originally Posted by CanAutM3

I was going with the information published in this thread: https://f87.bimmerpost.com/forums/sh....php?t=1497066

However, looking at it deeper and combined with the data provided by m4forum , I came to realize that hellrotm misquoted the rear M2C big brake rotor weight. He seems to have taken the front blue rotor weight for the rear grey one.

Recalculating with the revised M2C rear rotor weight I get those difference between the systems:
18.2lb Blue vs CCB
27.5lb Blue vs Grey
45.7lb Grey vs CCB

27~28lb unsprung weight is not negligible. If one goes through the trouble and cost of replacing rotors, calipers and pads, might as well go for an aftermarket BBK IMO, and not suffer the unsprung weight penalty. In your case, where it is only a question of swapping CCB rotors for the iron ones, yes it does make sense cost wise.

For reference:

Thanks for acknowledging and redoing the estimates. I think what's also confusing is Giro disc upgrade being thrown in the mix when discussing weights. When comparing apples to apples, you should compare gold/grey OEM 400mm rotors versus blue OEM rotors. Girodiscs are known to be heavier than the same sized OEM rotor.

I am assuming that OEM grey/red BBK is cheaper than an aftermarket BBK. By a lot. If that is a false assumption, I take back my recommendation to go OEM BBK vs aftermarket. I am also reading that OEM gold/red BBK are very high quality with titanium/aluminum pistons. Which makes me hope that expensive aftermarket BBKs are also equally well engineered.

[m4forum]

The major disadvantage with M2C on front is the restriction on 18" tires. Cost is much cheaper than BBK.
For clarification the gold calipers dont have titanium pistons. I am retrofitting my with SS pistons from Racing brake.

Piston rear gold caliper : 28x32 aluminum weight 38 grams.
Piston rear Racing Brakes : 28x32 SS weight 55 grams.

[USSEnterprise]

Originally Posted by m4forum

The major disadvantage with M2C on front is the restriction on 18" tires. Cost is much cheaper than BBK.
For clarification the gold calipers dont have titanium pistons. I am retrofitting my with SS pistons from Racing brake.

Piston rear gold caliper : 28x32 aluminum weight 38 grams.
Piston rear Racing Brakes : 28x32 SS weight 55 grams.

Yeah, you either pay more for an aftermarket BBK up front, or pay later through higher tire costs with OEM BBK.

Interesting information on the rear Gold caliper pistons. Do you happen to know what the front Gold pistons are made of?

[m4forum]

But I believe BBK on front still makes sense as resale price is very good and running cost is lower. For the rear I am convinced (so far) M2C is a great option.

I dont know the material for front gold piston but if somebody has it just remove the pads and scratch the inside of the piston (not functional area). if scratches is aluminum. I bet it is.

[CRRobert]

Anyone have links for the SS Pistons/better dust boots?

[m4forum]

https://racingbrake.com/

[r4dr]

Originally Posted by NYG

In general, you're correct but a soft pedal is not exclusively the compression of air in your lines. The expansion and stretching of rubber lines reduces hydraulic pressure significantly which also affects how much of the air you can actually compress. So if you apply the same pedal force, a stainless steel brake line with air will have higher hydraulic pressure than a hot rubber line with air. It's not misinformation, it's classical mechanics.

I'd agree with you in 99% of cases but overheating a PFC11 is not an easy task even on the F8x.

There are legitimate advantages to a quality aftermarket stainless steel brake line, but it's not because the stock lines on a modern M car cannot handle the pressure from the brake system and stretch out.