AP Racing weight savings vs. Carbon Ceramic

[FormulaMMM]

See post #20 for CCB refurbishment summary.

Intend to run through this set of stock pads, then probably replace the system with aftermarket iron.

Looking at AP Racing: https://www.essexparts.com/essex-des...-f87m2f80m3f82, https://www.essexparts.com/essex-des...36530mm-M2M3M4

My only hesitation on replacing the CC system is unsprung weight increase. Probably mental more than anything else, admit it, but I don’t want to increase weight on this car.

CC system saves 18.2# overall as compared to the stock F8X iron. (https://f87.bimmerpost.com/forums/sh....php?t=1307736) The CC discs are quite a bit lighter, but calipers heavier. (Fair to consider rotating mass more influential than caliper weight.)

AP Racing kit savings vs. F8X iron are as follows:

Front caliper(s) – 1.1# (2.2#)
Front disc(s) – 2.8# (5.6#)

Rear caliper(s) – 1.35# (2.7#)
Rear disc(s) – 5.7# (11.4#)

Overall AP Racing weight savings as compared to stock F8X iron = 21.9#. So, actually more than the Carbon Ceramic weight savings by my calcs, with the rotating mass caveat above.

Caliper weights are without pads, and the AP Racing calipers take much more meaty pads, so some of the weight savings will be negated there. But probably not much.

Anyone care to verify or inform where I’m going wrong? AP Racing weight data is in the “TECHNICAL SPECIFICATIONS” tabs at the links above.

thanks

[Docall]

I love mine. If you track it they are definitely worth it. I meant to weigh the iron discs before install, but forgot to. The Calipers are much less than stock. Rotors are only a little heavier than carbon ceramics. The kit overall is definitely lighter than stock ceramics if you go with the caliper that holds the smaller brake pad.

[VChenz]

Have you considered adding a brake cooling kit and better pads to the stock setup?

I'm not an engineer but wouldnt lighter iron rotors = less mass to absorb heat meaning they wouldnt necessarily be more effective because they heat up sooner?

The bigger calipers would help in terms of acting like a heat sink.

[FormulaMMM]

Originally Posted by Docall

I love mine. If you track it they are definitely worth it. I meant to weigh the iron discs before install, but forgot to. The Calipers are much less than stock. Rotors are only a little heavier than carbon ceramics. The kit overall is definitely lighter than stock ceramics if you go with the caliper that holds the smaller brake pad.

Thanks for the feedback. Believe about 6# heavier than CC per front disc, and 2# heavier per rear disc. Could offset with wheels & tires.

Originally Posted by VChenz

Have you considered adding a brake cooling kit and better pads to the stock setup?

I'm not an engineer but wouldnt lighter iron rotors = less mass to absorb heat meaning they wouldnt necessarily be more effective because they heat up sooner?

The bigger calipers would help in terms of acting like a heat sink.

Sure that would help, but ultimately I'll still be facing those CC replacement costs. The AP Racing kit costs nearly as much as a full CC system replacement, but over the long-term I'll be in better shape.

[SYT_Shadow]

Your math seems correct

The AP or PFC kit is a much better option for serious track work. It also allows 18" wheels as an added benefit.

Even if a CCB rotor cost $500 like a AP/PFC rotor I still wouldn't run them. If CCBs exceed operating temp they die faster than a regular AP/PFC rotor.

[CanAutM3]

Originally Posted by FormulaMMM

Fair to consider rotating mass more influential than caliper weight.

Just as a technical tidbit, the effect of rotating mass has no effect on unsprung weight, so the true effect on unsprung weight is the actual ~18.2lb.

Rotating mass only has an effect if the rotational speed of the rotor is changed (i.e during acceleration and braking). The rotating mass factor of brake rotors of this size is about 1.2x, so impact on the effective mass of the CCB on the total car while accelerating and braking is ~25lb (-33lb rotors x1.2+ 15lb caliper).

[FormulaMMM]

Originally Posted by SYT_Shadow

Your math seems correct

The AP or PFC kit is a much better option for serious track work. It also allows 18" wheels as an added benefit.

Even if a CCB rotor cost $500 like a AP/PFC rotor I still wouldn't run them. If CCBs exceed operating temp they die faster than a regular AP/PFC rotor.

Thanks. I’ve had good luck with CC systems for a few seasons and two platforms now, haven't smoked them. But the BMW replacement costs are stupid as compared to GM. I’d probably continue with the BMW CC system if discs were ~$1k like GM. The only stock BMW system I’ve ever run that works on track… Ironic that I’m looking to replace.

Originally Posted by CanAutM3

Just as a technical tidbit, the effect of rotating mass has no effect on unsprung weight, so the true effect on unsprung weight is the actual ~18.2lb.

Rotating mass only has an effect if the rotational speed of the rotor is changed (i.e during acceleration and braking). The rotating mass factor of brake rotors of this size is about 1.2x, so impact on the effective mass of the CCB on the total car while accelerating and braking is ~25lb (-33lb rotors x1.2+ 15lb caliper).

Good data for reference, thanks. Agreed on the unsprung weight numbers. Just seems a bit off to think that the BMW CC system isn’t more favorable from a dynamic standpoint than the AP. Considering where the weight savings are occurring (discs vs. calipers). You’d take the disc weight savings over caliper, yeah?

[SYT_Shadow]

Originally Posted by FormulaMMM

Thanks. I’ve had good luck with CC systems for a few seasons and two platforms now, haven't smoked them. But the BMW replacement costs are stupid as compared to GM. I’d probably continue with the BMW CC system if discs were ~$1k like GM. The only stock BMW system I’ve ever run that works on track… Ironic that I’m looking to replace.

A birdie told me a major race shop is looking at building replacement iron rotors for the CCB setup. Maybe you want to wait for that?

The CCB uses much better hardware than BMW typically uses. If you don't brake like a madman you can get a lot of use out of a set of CCB rotors even if you're fast.
The issue creeps up when you are specifically gaining time in braking zones

You could also just swap the front setup for a BBK instead

[FormulaMMM]

Originally Posted by SYT_Shadow

A birdie told me a major race shop is looking at building replacement iron rotors for the CCB setup. Maybe you want to wait for that?

The CCB uses much better hardware than BMW typically uses. If you don't brake like a madman you can get a lot of use out of a set of CCB rotors even if you're fast.
The issue creeps up when you are specifically gaining time in braking zones

You could also just swap the front setup for a BBK instead

I'd be all ears on that. Porsche GT track crowd regularly swaps CC for iron. Wish we had the same option

20-25 minute sessions I've found the GTS system faultless. Tire temps and pressures become unmanageable before brakes fade @ my home track.

[Gomeler]

Originally Posted by SYT_Shadow

A birdie told me a major race shop is looking at building replacement iron rotors for the CCB setup. Maybe you want to wait for that?

The CCB uses much better hardware than BMW typically uses. If you don't brake like a madman you can get a lot of use out of a set of CCB rotors even if you're fast.
The issue creeps up when you are specifically gaining time in braking zones

You could also just swap the front setup for a BBK instead

Two-piece rotors? AFAIK the upgraded M2C rotors fit/use the CCB caliper, so that is a heavy but cheaper option over the CCBs or AP Racing setup.

[SYT_Shadow]

Originally Posted by Gomeler

Two-piece rotors? AFAIK the upgraded M2C rotors fit/use the CCB caliper, so that is a heavy but cheaper option over the CCBs or AP Racing setup.

Yes, a race-worthy 2 piece setup. Like the PFC Direct Drive rotors which were so nice to have access to back in the E46 and E92 days

The M2C rotors are a great low cost solution. The GTS I spend a lot of time driving uses them. It's a nice 'no brainer' setup but is heavy and not the best for serious track use due to metallurgy, having 'holes' and weighing a lot more than it should.

Racing Brake also sells CCB replacement 2 piece rotors but I'm a little skeptical.

[FormulaMMM]

Originally Posted by SYT_Shadow

Racing Brake also sells CCB replacement 2 piece rotors but I'm a little skeptical.

More than $3k for the set and sold with a street pad.

Contacted them about CCB refurbishment service, which they promote. Just exploring options. Indicated they're still in experimentation phase with that.

If i were a gambling man... https://www.rebrake.de/preise/?lang=en

[SYT_Shadow]

Originally Posted by FormulaMMM

More than $3k for the set and sold with a street pad.

Contacted them about CCB refurbishment service, which they promote. Just exploring options. Indicated they're still in experimentation phase with that.

If i were a gambling man... https://www.rebrake.de/preise/?lang=en

Interesting... I have family in Germany...

My question is whether this service can fix the life indicators on the BMW CCBs. Those little round circles, 3 of them, that show how much life the rotor has left

[FormulaMMM]

Originally Posted by SYT_Shadow

Interesting... I have family in Germany...

My question is whether this service can fix the life indicators on the BMW CCBs. Those little round circles, 3 of them, that show how much life the rotor has left

I inquired. We'll see what the deal is.

Doubt the indicator restoration, but if I can chart the initial disc degradation and wear over X track days, could commit to doing it every couple seasons, or whatever the case might be.

[Gomeler]

Originally Posted by SYT_Shadow

Yes, a race-worthy 2 piece setup. Like the PFC Direct Drive rotors which were so nice to have access to back in the E46 and E92 days

The M2C rotors are a great low cost solution. The GTS I spend a lot of time driving uses them. It's a nice 'no brainer' setup but is heavy and not the best for serious track use due to metallurgy, having 'holes' and weighing a lot more than it should.

Racing Brake also sells CCB replacement 2 piece rotors but I'm a little skeptical.

2-piece irons for the CCB calipers could be a very interesting choice depending on availability. I'm either going M2C rotors or AP Racing 9668/9449 depending on how much my enduro schedule takes out of the frivolous toy budget. Having something between the two could be very appealing.

[SYT_Shadow]

Originally Posted by Gomeler

2-piece irons for the CCB calipers could be a very interesting choice depending on availability. I'm either going M2C rotors or AP Racing 9668/9449 depending on how much my enduro schedule takes out of the frivolous toy budget. Having something between the two could be very appealing.

Yes, very interesting indeed.

Meanwhile on the CS (not the same, I know) I run the PFC Z54 front bbk and the AP 9449 rear bbk.
The GTS will end up either with the 2 piece irons or more likely the same PFC/AP setup my CS has.

[CanAutM3]

Originally Posted by FormulaMMM

Thanks. I’ve had good luck with CC systems for a few seasons and two platforms now, haven't smoked them. But the BMW replacement costs are stupid as compared to GM. I’d probably continue with the BMW CC system if discs were ~$1k like GM. The only stock BMW system I’ve ever run that works on track… Ironic that I’m looking to replace.



Good data for reference, thanks. Agreed on the unsprung weight numbers. Just seems a bit off to think that the BMW CC system isn’t more favorable from a dynamic standpoint than the AP. Considering where the weight savings are occurring (discs vs. calipers). You’d take the disc weight savings over caliper, yeah?

As I posted earlier, the effect of the rotating mass of the rotors is rather negligible on acceleration and braking and has zero effect on handling. Further, the BBK's smaller diameter compared to the CCB (372mm vs 400mm) offsets the CCB's lower weight impact on rotating mass. In the end, what really matters is unsprung mass on the handling. So the BBK would get my vote just from a performance stand point.

[FormulaMMM]

Originally Posted by CanAutM3

As I posted earlier, the effect of rotating mass on the rotors is rather negligible on acceleration and braking and has zero effect on handling. What really matters is unsprung mass on the handling. So the BBK would get my vote.

Got you. Do you have an estimate for the rotating mass factor of our wheels & tires?

[CanAutM3]

Originally Posted by FormulaMMM

Got you. Do you have an estimate for the rotating mass factor of our wheels & tires?

Mass factor varies with the part geometry (mostly how far the mass is located from the roration center) and speed ratio (i.e. The engine flywheel has a huge effect in first gear).

For 19"-20" wheels and tires, figure roughly 1.4x for the wheel and 2.0x for the tire.

[FormulaMMM]

CCB refurbishment update --

I’ve had a handful of exchanges with Wolfgang at Rebrake.de. He’s responsive, seems very decent and knowledgeable.

Enthusiastic about the possibility of retaining the GTS’s stock CCB system, and finding a path to relatively economical ongoing CCB track use. Here are highlights of our conversation:

- BMW CCB disc refurbishment is absolutely possible.
- The disc structure is the same as Porsche’s Gen 4 PCCB discs, which Rebrake refurbishes all of the time.
- Characteristics stay the same post-refurbishment – brake feeling, brake power. Still use the stock GTS pads.
- Refurbishment results in an as new disc. Full lifetime once again.
- Refurbishment can be repeated 3-4x.
- Expect ~35 working day turnaround time.
- For track use, brake cooling is recommended. Says CCB lifespan is extended significantly with cooling. (I’ll probably install ducts this winter.)

Current pricing w/ exchange rate: $1,660 per front disc. $1,549 per rear disc. Rebrake can arrange DHL pickup w/ insurance. So price for two refurbished front discs is less than ½ of disc replacement cost ($7,655 via ECS).

Figure somewhere in the neighborhood of 2:1 lifespan front discs to rear (tbd). Could do 2 front disc refurbishments and 1 rear before equalling the price of a suitable BBK like AP Racing’s. (Not an argument against the AP Racing kit.)

I’m not keen on abandoning the CCB system for a variety of reasons, not the least of which is it’s the first stock BMW system that I’ve found awesome on track.

I also think in general we’ll see more CCB solutions moving forward. OE replacement costs might go down, aftermarket part solutions, increasing availability of refurbishing services, etc. Found this while researching: https://www.autoquestcars.com/custom-11 (Note refurbishing element.)

Anyways, FYI for the community. I like the sounds of it. As I said above, first way I’ve identified to apparently achieve relatively affordable CCB track use.

[Gomeler]

That's pretty great news, and the pricing isn't absolutely wallet breaking. Still have mixed feelings on the CCBs, can't just caliper them to determine when is a good time to refurb them, but that's just a nitpicky issue. Are your fronts getting close to a refurbishment window, or planning on running them through 2020?

Good news on the brake cooling, I wasn't sure if I should add some ducting to the CCBs, sounds like I'll be fabbing something this winter.

edit: "$600 per rotor for refurbishment (plus shipping)" for those Porsche rotors. That makes this an even more interesting concept if rotor refurb gets down to $1200-$1500 for every 4k-5k miles. Hopefully prices keep coming down on refurb costs.

[FormulaMMM]

Originally Posted by Gomeler

That's pretty great news, and the pricing isn't absolutely wallet breaking. Still have mixed feelings on the CCBs, can't just caliper them to determine when is a good time to refurb them, but that's just a nitpicky issue. Are your fronts getting close to a refurbishment window, or planning on running them through 2020?

Good news on the brake cooling, I wasn't sure if I should add some ducting to the CCBs, sounds like I'll be fabbing something this winter.

edit: "$600 per rotor for refurbishment (plus shipping)" for those Porsche rotors. That makes this an even more interesting concept if rotor refurb gets down to $1200-$1500 for every 4k-5k miles. Hopefully prices keep coming down on refurb costs.

I agree the inability to monitor wear with precision isn't ideal. (There are the visual indicators: https://f80.bimmerpost.com/forums/sh....php?t=1115439)

But based upon everything I've learned, under reasonable track use conditions you're definitely talking multiple pad replacements before the discs are done. At minimum a couple of pad replacements. My approach might be to run through 2 sets of pads (currently on original set), then conduct a disc evaluation, see if it's refurb time or whether I can chew through at least a third set of pads.

From there I'd have a clear reference point for disc refurbishment moving forward.

Yes, exactly on the Porsche solution and prospect of greater availability, decreasing costs. In combination with the CCB performance, all of it is encouraging enough for me to probably hold tight on the system.