When Lightweighting Goes Too Far

A couple months ago, I stopped in at my local BMW dealer in Ann Arbor to pick up some grommets for my project Z3 Coupe. When I first walked in, I was taken aback by a flat gray M3 on the showroom floor. It was a stunning combination of one of my favorite shades, complimented by a subtle carbon fiber splitter, trunk spoiler, and diffuser. The thin Y-spoked staggered-diameter wheels did little to cover the potential of the giant carbon ceramic brakes, while the black and light grey leather had enough contrast to look more inviting than the all-too-prevalent black interiors. This was all adding up to look like a particularly well-optioned M3.

I looked inside again, and saw a thick-rimmed Alcantara steering wheel, some more Alcantara trim, and a red Start/Stop button. I looked to the rear window, containing the window sticker, for the remaining explanation that I needed.

Illustration for article titled When Lightweighting Goes Too Far

This was the hardcore BMW M3 CS. And I was about to discover how the philosophy of lightweighting could be taken too far.

Now, at risk of having my 15-year BMW CCA membership revoked, I’ll admit that I hadn’t exactly realized that an M3 CS was a thing. So, I looked at the sticker more closely.

There weren’t many options on this car, but the ones that it did have were significant. That Lime Rock Grey paint was $5,000. The M Carbon Ceramic brakes? Those are $8,150. An “Executive Package” brought a power rear sunshade, manual side shades, park distance control, adaptive LED lights, auto high beams, and heads-up display for a comparatively reasonable $2,600. The grand total was $114,995.


I gasped. A hundred and fifteen grand for an M3?

Illustration for article titled When Lightweighting Goes Too Far

It was then that the manager of the store came over and asked what I thought. Having missed the memo on the car, I asked him what was special enough about it to command that price tag.

He excitedly detailed for me the weight-savings plan that the car had gone through. The dual-zone climate control and Comfort Access system had been omitted. The hood and roof were replaced with carbon fiber-reinforced plastic pieces, while some additional carbon fiber aero bits were added, including a splitter, lip spoiler, and rear diffuser.

A lightweight stainless-steel exhaust system was also installed, which changes up the soundtrack quite notably, while yet other features were deleted. With the lightweight M sport seats as standard and the optional carbon ceramic brakes, a claimed 66-pound weight reduction was realized from the lesser Competition Package M3; the CS weighs in at 3,494 pounds.

“Ah,” I responded. “I’ve seen this tactic before with Porsches. You pay more to get less.”


Illustration for article titled When Lightweighting Goes Too Far

“No!”, he replied, before proceeding to tell me about the additional power of the S55 twin-turbo inline-six. It has 453 horsepower and 443 lb-ft of torque in the CS, a nice bump over the 425 HP and 406 lb-ft of the standard M3—or the 444 HP and 406 lb-ft of the M3 Competition.

While I’ll acknowledge that the CS has more power, I didn’t figure that it’s a significant enough difference to notice, on its own. Maybe, when compared with a modest weight savings, it would add up to something.

Still bowled over by the price, I climbed inside to get a feel for the seating position. I dropped down, straddling the outer bolster. As I repositioned my elbows and went to lift myself up with my right elbow, there was no support there to be found. This resulted in me falling to the right, tumbling about the car.

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Once I regained consciousness upside down in the back seat, I assessed my surroundings. What I found must have been an assembly error in the factory: They forgot to install the center console and armrest.


Of course, I’m mildly exaggerating; said armrest was intentionally omitted in the name of weight savings. On a $115,000, 3,500-pound luxury sedan. Which was also equipped with a power rear sunshade. The armrest was replaced with what appeared to be an Alcantara-wrapped piece of 2×4 lumber between the front seats.

Needless to say, I found it to be completely inexcusable that such a heavily-used item had been omitted for this car, while keeping so many other creature comforts.

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Though I was still shaking my head in frustration, my subsequent discussion with the manager led to him offering to let me take each version of the M3 for a quick evaluation drive to compare them all for this story. That is, a base M3 with the DCT gearbox (these start around $67,450, plus $2,900 for the DCT), an M3 Competition Package with a six-speed manual (bump to about $72,200 before other options) and this center-consoleless M3 CS with the DCT ($98,250 starting and, yep, $115,000 as equipped here.)

When I was able to arrange another visit, I stopped back in and the now-manager, Mo Beidoun, prepared the cars and provided me great hospitality. In fact, the base M3 that I used was Mo’s personal car.

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Overall, the Competition Package was a really nice, cohesive, upgrade over the base car. The fun factor went up with the outright handling limits, with harshness going down and ride quality improving.

Not only did the Comp have better mid-range than the base car, but it was the top end that felt more alive. Where the base car’s power curve flattened a bit above 6,000 RPM, the Comp felt like it wanted to pull all the way up to 7,000. On top of that, it sounded a good bit sweeter, though these days I can’t tell you how much of that change came from the exhaust or if it was synthesized through the audio system.

The chassis response on the Comp really shone over the base car, with less roll in the front that was better balanced with the roll stiffness at the rear of the car. Along with a slight decrease in understeer, the limits felt more approachable despite there being a bit more grip available. These calibrations don’t always equate to more fun in the real world, but in this case, it does.

The only potential downside was that, when the limits were exceeded, the rear breakaway was slightly more abrupt. But, that could have been more of a characteristic of the different tires between this and the base car.

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The improved front-end response communicated well through the steering wheel when it was in Sport mode, where the steering efforts built up nicely in response to the load being generated at the tires as I steered in. Sport+ felt too heavy for my tastes, making the steering response feel slow relative to my input, whereas Comfort mode was too light and lacking in return damping, making the steering act too quickly relative to the weight transfer and response of the tires and suspension.


This was a typical case where there’s a “right” mode, which is ideally suited to the vehicle, and then “more” and “less” modes that are frequently exaggerated just so that the owners can tell that something has changed.

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Interestingly the ride of the Comp package was a nice improvement over the base car, with surprisingly little harshness, even in Sport+ mode, despite the shorter-sidewall 20-inch tires. Here, the damper tuning modes were more closely aligned. Comfort mode took away the bit of float that the base car exhibited in the same mode, while each of the three modes were more composed and less upset by mid-corner road inputs.

I really saw no downsides, aside from the busy wheel design that I don’t care for. But these gains are possible if you’re willing to pay for them.

Onto the CS.

Illustration for article titled When Lightweighting Goes Too Far


A nine horsepower and 37 lb-ft bump over the Competition package doesn’t sound like much. But, when paired with the weight savings and the seven-speed DCT, the CS has pulls from any RPM until you get scared or regain your sanity and back off. Only when driven back-to-back with the Competition was the CS was noticeably a bit quicker. It did sound even better inside the car, but I can’t tell you how much of that was authentic vs. synthesized.

The brakes were the Brembo-supplied carbon ceramics with six-piston front calipers and four-piston rears. I’m not embarrassed to say that no significant difference stood out to me in their actual stopping performance. While I’ll admit that I wasn’t highly focused on evaluating the brakes in my brief drives, there is a good explanation for this.

Now, stay with me here, in case this is a new concept to you, but the brakes don’t stop the car. The tires do. The brakes just transfer kinetic energy to thermal energy. It’s the tires that apply the forces to decelerate the vehicle. So, as long as the tires are the limiting factor, especially on the street, the brakes are rarely being exercised to their full capacity.

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Therefore, considering that the base M brakes are already highly capable and have great feel, this is hardly surprising. I will note, though, that I experienced an odd whirring noise when coming to a stop in the Comp package car that I was not able to identify, which was not present in the base car or the CS.

There is a more significant performance benefit to the carbon ceramic brakes than stopping power, though, and that comes in the form of reduced rotating and unsprung mass. According to measured data that I found on a forum, the calipers weigh 14.8 pounds more in total, but the discs are 33 pounds lighter, netting an 18.2-pound weight savings.


But the real gain is losing 8.7 pounds of rotating mass on each front corner and 7.8 pounds on each rear. That’s 33 pounds less mass that needs to be spun up and down with acceleration and braking. Furthermore, that’s 8.7 pounds less spinning mass in each front wheel that’s resisting being turned due the phenomenon known as “gyroscopic precession”.

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Granted, this is mainly a factor when turning in at high speeds, but it’s an advantage nonetheless.

Now, did the reduction to unsprung and rotating masses result in a noticeable difference in the CS? Independently, the answer would be no.

However! I found them to be a contributor to the piecemeal approach to pushing the capabilities of the car. For similar benefits as lightweighting the brakes, among others, the CS was fitted with smaller 19-inch wheels in the front, while retaining 20-inch wheels in the back.

The front tires are also 10mm narrower, according to the sidewall dimensions, but are able to do their job more effectively with less weight to manage, as well as gaining a bit more sidewall compliance.


Combined with retuned suspension, the CS gained mechanical grip, with a corresponding reduction in understeer, and all of the turn-in response of the Comp, despite the taller front sidewalls. The rear tires had a more progressive breakaway than the Comp, while the damper tuning maintained composure and grip through mid-corner inputs, inspiring confidence through quicker sweepers.

The DCT in the CS may be the best-tuned application of a dual-clutch gearbox that I’ve driven, and was a huge improvement over the same transmission in the base car. In the most aggressive settings, the shifts were not only done by the time you released the paddle, but also smooth. No artificial surges on up-shifts that do little other than to upset the chassis. This was tuned to simply work well, with minimal disruption to power transfer to the rear tires, performing better in both normal and aggressive driving.

Each of the steering modes felt more closely tuned to the best-balanced Sport mode, which made Sport+ and Comfort modes usable, if one so desired. It seemed clear that BMW was turning down the gimmicks in the powertrain and steering and focusing on creating authentic mode options.

The ride suffered, though, as the trade-offs to making the CS more performance-focused were realized. Like the steering, each of the three suspension modes were more closely tuned to each other, but they all had considerably more rebound damping control than in the Comp.

While critical for maintaining grip in corners, it created quicker motions and more “tug” when coming over small crests or through drops in the road. There was also noticeably increased impact harshness in all modes, which surprised me since the CS offered more front tire sidewall.

It was easy to see the progression of chassis tuning strategy between each package when I had the ability to drive them all back-to-back. The CS was clearly a more focused track weapon, but at the expense of road comfort. I couldn’t help but ask myself if it a worthwhile tradeoff.


Inside the CS, I was planted in the same perfectly-bolstered open-back sport seats as in the Comp package. Meanwhile, my hands were wrapped around an Alcantara-wrapped version of the same steering wheel, though it’s not heated in the CS.

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I’ll also say that I don’t think Alcantara belongs on a steering wheel unless it’s a racecar where you’re wearing gloves. There’s just no way to keep the oils in your hands from deteriorating them in street use. And, if I wanted to take my right-hand off the wheel to preserve said Alcantara, or to simply relax, I’d really like to rest this arm somewhere. This creates a Ricky Bobby “I’m not sure what to do with my hands” scenario, since there’s no freaking armrest.

In addition, the CS has omitted dual zone climate control and its digital display, as well as Comfort Access. Those are pretty standard features for an average middle-management silver-on-black 330i xDrive on lease.

But the Executive Package ($4,100) on this car added back in Park Distance Control, Adaptive Full LED Lights, Automatic High Beams, Head-up Display, Power rear sunshade, and Rear manual side window shades.

It was this dissonance that I was contemplating as I pulled back into the parking lot at BMW of Ann Arbor. As I got out, I saw the illuminated ///M3 badges that adorned the seat backs with impressive color and definition. It was a really cool feature that solidified my assessment of the M3 CS.


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At $115,000, if this car was going to be offered with all these sorts of luxury items, it’s clearly intended to be a street car. The fact that it’s the best-handling, fastest and most fun F82 M3 does not overcome the degradation to ride quality, and the lack of a center console armrest.

Colin Chapman’s often-cited mantra to “simplify, then add lightness” is a narrow-minded pursuit of outright performance, with little consideration of the implications to the rest of the car. In the case of Lotus, some drivers died in crashes in his fragile cars. In modern road cars, there are numerous less-deadly trade-offs to be considered beyond outright performance numbers.

Illustration for article titled When Lightweighting Goes Too Far

While it’s easy to value a car based on its performance figures, what it takes to achieve lighter weight and sharper handling does not come for free. Whether selecting a new car or modifying an existing one, every performance aspect comes with trade-offs. The magic is in optimizing the car for its intended uses, while minimizing the compromises.

In the case of the M3 CS, BMW overvalued the benefit of removing the center console and tuned the suspension with too much emphasis on track performance for a five-passenger luxury sport sedan. For evidence of this, I find 93 new 2018 M3 CS cars still in inventory, as of this writing.


If I could afford any M3, I’d go with the Competition Package instead and do something irresponsible with the $30,000 left over. Like stuff a V12 into a Z3 Coupe.

Anthony Magagnoli is a professional race driver who runs Drive Faster Now, and a former Vehicle Dynamics Performance Engineer at Fiat Chrysler. He is a NASA Spec E30 National Champion, Pirelli World Challenge TC Rookie of the Year, and a gifted karaoke singer.

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