Carbon Ceramic brakes

[CanAutM3]

Originally Posted by stressdoc

Apologies if this information has been posted previously.
Do we know the total weights, rotors & calipers, for the CCBs & standard CIs?
Thanks!

I have not seen the total weights listed, but there are references to the delta weight between the CCB and the irons.

Total weight difference is ~14.5lb (3.6lb per corner) according to this reference and rotating mass reduction in 12.5kg (6.9lb per corner) as specified here.

So I deduce that the CCB calipers/pads (and mounting hardware) are ~3.3lb heavier.

[CanAutM3]

Originally Posted by CSBM5

...and the other component that is just as important is the radius of gyration of the wheel/tire assembly which will clearly be larger (worse) for the 19" versus the 18".

Similarly, people should ask BMW to provide not only the mass comparison for the brake rotors, but also the radius of gyration comparison. Unfortunately, since few of the public have an engineering background, comparisons of dubious value are easy to swing these days.

The inertia of the wheel/tire assembly cannot be automatically assumed to be worse on a 19" setup vs a 18" setup. It is important to compare the actual weight of the wheel tire combo. For the same rolling diameter, the 18" tire is often heavier than the 19" one. This added weight on the tire can offset the lower inertia of the smaller wheel (the tire weight is distributed even further away from the center of gyration compared to the wheel).

[CanAutM3]

Originally Posted by M4TW

We both know that stopping distance is determined by tires since both systems are capable of fully engaging the ABS.

Not necessarily.

It is not because a brake system is able to lock a tire that it is able to extract the maximum braking force from that tire. At some point, a brake system becomes saturated with heat and it is no longer able to generate the necessary dynamic friction at the pad/disc interface to fully utilize the tire's grip. On a poor brake system, this could happen within a single hard stop. Applying more brake force just results in lockup even if the tire could still handle more grip. This is the definition of fade and why longer braking distances are needed when the brakes start to fade. On faded brakes, it is still possible to lockup the wheels (or get ABS to engage).

Originally Posted by M4TW

• Fade resistance (more than a foot difference of degradation (between the two) of stopping distance after repeated trials);
• Wear resistance under normal track use; and
• Long term costs.

(negatives):

• Standard brakes in high-performance vehicles offer equivalent stopping distances;
• Standard brakes in high-performance vehicles offer acceptable fade resistance;
• Price; and
• Higher optimal operating temperature means that there is less braking feel during the first part of pedal travel - especially when cold.

(positives)

• Heat resistance
• Warp resistance
• They don't corrode, even when in contact with water or salt in the winter seasons;
• Guaranteed disc life of 93,000 miles for road use and 2,400 miles for extreme track use;
• They look pretty cool;
• 50% lighter than cast-iron discs in unsprung weight and should improve handling and driving dynamics; and
• Low mass rotors allow superior suspension tuning and consistent braking on the track.

My perspective on a few points:

See the Car & Driver brake test results here. The braking distances and resistance to fade was nearly identical for the iron and CCB equipped 911s.

As far as the reduction of equivalent mass for the CCB vs the iron on the F8X, I figured about a 20lb reduction on the whole car through a rough calculation. This is negligible IMO. BTW, rotating mass reduction has very little impact on handling if at all. It will help acceleration and braking, but 20lb worth...

Discs sized like the ones found on the F8X do not warp. When folks get brake shudder, it is more likely pad deposit from poor brake management. CCBs will likely be less prone to pad deposit due to the more aggressive pads they use.

I drive my car 4 seasons and corrosion on the discs has never been an issue for me (and they do put a bloody lot of salt on our roads in winter ), so I am not even sure why this is brought up.

From a performance point of view, IMO, the greatest benefit of the CCB is the 3.6lb of unsprung mass reduction per corner. Not huge, but present nonetheless.

As with any option on these cars, there is no right or wrong answer IMO. People often speak in absolutes. I think it is healthy and informative to have the debates over the pros and cons of each option to help guide us in our choices, but we seem to be getting too much of "you're crazy if you get that option" or "you're totally stupid if you don't get this option". We each have our own reasons to go or not go with certain options. If you fancy the CCB and you think it will give you $8500 worth of joy, go for it. Heck, I am getting the $2000 LEDs just for the bling.

[GregW / Oregon]

Originally Posted by myzmak

....someone sure became a convert.....

I would have bit if it would not have delayed my build.

[stressdoc]

Originally Posted by CanAutM3

From a performance point of view, IMO, the greatest benefit of the CCB is the 3.6lb of unsprung mass reduction per corner. Not huge, but present nonetheless.

If it was >3kg per, then I would consider CCB more seriously.

[M4TW]

Originally Posted by myzmak

....someone sure became a convert.....

Well, as you know converts always sing the loudest in church. In spite of Swamp's and CanAutM3's best efforts to the contrary, I just refuse to sing the "blues".

Originally Posted by swamp2

Well you've stacked the deck too in the above. Are you saying you are good to go with 3/4 from my previous list? If so I'm partial to AleSmith IPA. If, however, your criteria are the ones above we probably can't even arrive at mutually agreeable terms for a bet.

As for your #1 and #2 the CSiC system will likely outperform the factory stock system, but here is the key, and you probably know this, by a very small margin and not margin of any significant practical difference.

Well it seems we both are too cagey to get caught up in a sucker bet. I'd still buy you a beer though.

Originally Posted by swamp2

Last but not least don't forget durability as a significant negative. CSiC rotors are significantly more prone to chips which can occur from hard road debris (stones/pebbles) and slight "mishandling" during regular maintenance (any time wheels are removed or tools contact the rotors). Chips above a certain small threshold size typically mean a firm recommendation for a full rotor replacement.

if you throw chips at me, I'll throw brake dust at you - neither of which was mentioned in the article. I know you have to be careful when changing tires etc but there just doesn't seem to be that many reports of M5/6 owners finding that these disc's have a glass jaw when it comes to ordinary use. On the other hand, the brake dust thing is real.

Originally Posted by CanAutM3

I have not seen the total weights listed, but there are references to the delta weight between the CCB and the irons.

Total weight difference is ~14.5lb (3.6lb per corner) according to this reference and rotating mass reduction in 12.5kg (6.9lb per corner) as specified here.

So I deduce that the CCB calipers/pads (and mounting hardware) are ~3.3lb heavier.

Thanks for saving me the work of digging up your calculations. However, how would you convert 14.5 lbs of unsprung weight to sprung weight? What factor would be appropriate? 1:1, 1:2, 1:4, 1:10? Unsprung weight savings should be magnified in the handling characteristics of the car no?

Further, there was a big ballyhoo about the 40% reduction in the rotating mass of the drive shaft improveing engine responsiveness. Wouldn't a further reduction of 27.5 lbs add to that? Or do we only use half of that representing the back wheels?

I'm not being rhetorical here. I have a genuine interest in your reply.

Originally Posted by CanAutM3

I drive my car 4 seasons and corrosion on the discs has never been an issue for me (and they do put a bloody lot of salt on our roads in winter ), so I am not even sure why this is brought up.

I think it was mentioned in the press clip you cited that this matters for low mileage or infrequent use otherwise the discs seem to be cleaned well enough through use. I had a look at my steels on my 335 and their still shinning in spite of a brutal winter.

I agree that each person considering this option has to apply any information on these forums to their personal circumstances and there are no wrong answers when it comes to preferences.

[CanAutM3]

Originally Posted by M4TW

Thanks for saving me the work of digging up your calculations. However, how would you convert 14.5 lbs of unsprung weight to sprung weight? What factor would be appropriate? 1:1, 1:2, 1:4, 1:10? Unsprung weight savings should be magnified in the handling characteristics of the car no?

Further, there was a big ballyhoo about the 40% reduction in the rotating mass of the drive shaft improveing engine responsiveness. Wouldn't a further reduction of 27.5 lbs add to that? Or do we only use half of that representing the back wheels?

I'm not being rhetorical here. I have a genuine interest in your reply.

There is no conversion for unsprung to sprung weight that I know of. The improved handling provided by lower unsprung weight does not translate back to the total weight of the car per se.

You might have missed the link I provided in my previous reply. Some of the answers you seek are there.

As for the driveshaft, the impact of the reduced inertia on equivalent mass is amplified by the square of the final drive ratio. So inertia reduction on the driveshaft has ~11 times more impact than inertia reduction on the wheels/tires on the F8X. But since the diameter of the driveshaft is fairly small, reducing the weight does not have huge impact on inertia. The mass factor of the driveshaft is about 1.1, which is less than the wheels and tires. IMO, the increased responsiveness provided by the CF driveshaft comes from both, the increased stiffness and the reduced weight.

[CanAutM3]

Originally Posted by swamp2

As you hinted in this and the next post, it is both the weight of the combined wheel/tire assembly that matters and also it moment of inertia. Since we never have the latter we can focus on the former and make reasonable assumptions about the moment of inertia. Such assumptions allow us to make conclusions that a one pound lost in each wheel is like 8 lbs of total lost mass from the perspective of acceleration.

Not sure how you get a factor of 8x for the tire/wheel combo. I get a factor of ~2x for a 275/35R19 tire and ~1.5x for a 19" wheel. The mass factors do not change drastically going to an 18" setup.

EDIT: OK, got it. One pound on EACH wheel times a 2x factor times 4 wheels on the car equals 8lb total on the car.

[CSBM5]

One additional thing to keep in mind when discussing inertia reduction is that it is only effective when trying to accelerate or decelerate the rotating mass(es). Acceleration is highest in 1st gear of course and drops off as speeds increase, so reduction in inertia means less and less as speeds increase/acceleration decreases.

This works in reverse for braking of course since then inertia has its biggest effect at the highest speeds when you attempt to slow down.

I know many here understand this thoroughly, but the majority on the board likely do not.

[CanAutM3]

Originally Posted by CSBM5

One additional thing to keep in mind when discussing inertia reduction is that it is only effective when trying to accelerate or decelerate the rotating mass(es). Acceleration is highest in 1st gear of course and drops off as speeds increase, so reduction in inertia means less and less as speeds increase/acceleration decreases.

This works in reverse for braking of course since then inertia has its biggest effect at the highest speeds when you attempt to slow down.

I know many here understand this thoroughly, but the majority on the board likely do not.

The same can be said about the total vehicle mass when looking at acceleration. This is why "equivalent mass" is so convenient, it depicts well the impact that rotating mass has on the overall mass of the vehicle and can be used in F=mea (where me is equivalent mass).

[FTS]

I you guys are over analyzing this CCB vs. steel thing CCB costs in the long run are not as high as you make it out to be, they work very well at every temp range and because they dissipate heat faster fluid and pad fade is nearly non-existent. For me the biggest benefit is the caliper design that is better than the steel offered and since purchase price is very close to a full BBK system, it is worth it. Of course it's your money, spend it as you wish, I am glad we have the option though.

[Walt Dockery]

Originally Posted by FTS

you guys are over analyzing this CCB vs. steel thing

+1

Very good OP/review, it's too bad the thread went down the toilet thereafter.

[stressdoc]

Despite a few pleas to the contrary, I think the CCB / Cast iron discussion should be moved into its own thread.

[M4TW]

Originally Posted by stressdoc

Despite a few pleas to the contrary, I think the CCB / Cast iron discussion should be moved into its own thread.

I am not stressed about that. I will wait for the move before taking the discussion further down the rabbit hole.

[CanAutM3]

Originally Posted by stressdoc

Despite a few pleas to the contrary, I think the CCB / Cast iron discussion should be moved into its own thread.

Agreed. It should be merged with one of the existing threads.

[M4TW]

Originally Posted by CanAutM3

Agreed. It should be merged with one of the existing threads.

I'm back in the cellar with more questions.

[swamp2]

Originally Posted by FTS

I you guys are over analyzing this CCB vs. steel thing CCB costs in the long run are not as high as you make it out to be

Maybe replying will further speed the eventual movement of the side discussion into a new home.

I'm not sure I follow your logic. Where have I overstated the cost of the CSiC system in any prior analysis? Here it is in more detail with much more precision:

The vast majority of the unfavorable cost comparison is simply the $8k asking price vs. $0 for the standard brakes. For the moment forget about any additional cost for the CSiC system whatsoever (no parts, no maintenance, etc.). Assume only the base system will need parts replaced. Even if the CSiC rotors and matching pads outlast the base system by a factor of 300% (which according to various data I have seen is very unlikely) you could replace the pads and rotors entirely 3 times and then the pads another 3 times and still be under that $8k. This does assume you do your own labor. If the labor is about $250 per job it would bring it down to 2 additional complete sets of pads and rotors and and extra 2 complete sets of pads in between. You'd then still have almost $2k left in favor.

This obviously does not account for the time when the CSiC rotors will have to be replaced. A set of rotors alone will likely be more than the $8k initial sticker price of the upgrade because that upgrade is subsidized by the cost savings of not being sold the base brake system. Can anyone confirm the list price for a complete set of CSiC rotors yet. Is this info available publicly on the web yet?

[FTS]

I change my rotors every year, pads three times a year, brake fluid each month accompanied by caliper bolts as well, and calipers every 2 years front and 3 years the rears. The steel rotors cost $1500 per front set (not BMW, but I am sure they will be very similar) and $1100 for rear set, pads are $800 per front and $700 rear, caliper bolts $12/bolt x 8, brake fluid $75, front calipers are $3K, rears are $2.5K. So, what does that add up to? Over 10K for brakes for me, I wish I was exaggerating. With the CCBs I expect to save quite a bit during the free maintenance period, and after that switch to steel rotors, and be done with it

Am I over doing it, probably not. Each time I hit the brakes from 150-155 mph and never worry about it (there has been a single exception that did not end well, still...), I take the check book out happily. At the same time, I think we have established that if you are not tracking, CCBs are overkill, I am not contesting that at all. At the same time, I am convinced without a doubt that the stock steel brakes will not perform for me at all, I just do not like the caliper design.

My point in my post really is that everyone's perspective, experiences and needs/usage are different, it is not worth over analyzing couple thousands here or there, braking distances, weight, etc. Most won't go for CCB due to cost, some will do, we'll get first hand data accumulated in a year or two, and discussion will be over. We went through this on the Porsche boards with each gen PCCBs and gosh it was so endless that really did not provide much IMHO.

[M4TW]

Originally Posted by FTS

I change my rotors every year, pads three times a year, brake fluid each month accompanied by caliper bolts as well, and calipers every 2 years front and 3 years the rears. The steel rotors cost $1500 per front set (not BMW, but I am sure they will be very similar) and $1100 for rear set, pads are $800 per front and $700 rear, caliper bolts $12/bolt x 8, brake fluid $75, front calipers are $3K, rears are $2.5K. So, what does that add up to? Over 10K for brakes for me, I wish I was exaggerating. With the CCBs I expect to save quite a bit during the free maintenance period, and after that switch to steel rotors, and be done with it

Am I over doing it, probably not. Each time I hit the brakes from 150-155 mph and never worry about it (there has been a single exception that did not end well, still...), I take the check book out happily. At the same time, I think we have established that if you are not tracking, CCBs are overkill, I am not contesting that at all. At the same time, I am convinced without a doubt that the stock steel brakes will not perform for me at all, I just do not like the caliper design.

My point in my post really is that everyone's perspective, experiences and needs/usage are different, it is not worth over analyzing couple thousands here or there, braking distances, weight, etc. Most won't go for CCB due to cost, some will do, we'll get first hand data accumulated in a year or two, and discussion will be over. We went through this on the Porsche boards with each gen PCCBs and gosh it was so endless that really did not provide much IMHO.

Post of the year on this topic as far as I am concerned. Though, I must ask, at the rate that you are chewing through brakes, do you live at a track or on top of a mountain?

A point that you make well, that Swamp missed above, is that the owner of the ceramics is not obligated to go back to BMW or even to ceramics when they finally wear out (especially if we are now outside warranty). Hopefully there will be good aftermarket CCB options then and/or the price will come down enough to make the cost/benefit scale more palatable.

[swamp2]

Pricing for rotors is available. Should be very close to what dealers will charge.

F, CSiC, $4727; cast iron, $438
R, CSiC, $4357; cast iron, $377

Over a full order of magnitude more expensive. Absurd...

Source, lists weights of components as well, nice for nerd inquiries...

[consolidated]

Originally Posted by swamp2

Pricing for rotors is available. Should be very close to what dealers will charge.

F, CSiC, $4727; cast iron, $438
R, CSiC, $4357; cast iron, $377

Over a full order of magnitude more expensive. Absurd...

Source, lists weights of components as well, nice for nerd inquiries...

Expensive replacements, cheap option.

[CanAutM3]

Originally Posted by swamp2

Pricing for rotors is available. Should be very close to what dealers will charge.

F, CSiC, $4727; cast iron, $438
R, CSiC, $4357; cast iron, $377

Over a full order of magnitude more expensive. Absurd...

Source, lists weights of components as well, nice for nerd inquiries...

...but expected.