As cool as this naked chassis is, I would rather have a 2012 McLaren MP4-12C at home in my driveway, up on jackstands with the wheels off. Why? Getting one to my home would involve me driving it, of course.
But McLaren isn't quite ready to hand out keys just yet, not even for those who come armed with a quarter-million dollars in cash. No, even the paying customers must wait.
In this unfortunate reality, a de-bodied protoype like this is a more-than-acceptable substitute.
Already, we can see something interesting. The McLaren MP4-12C is not a unibody machine: the car gets all the strength it needs from what lies beneath the skin. The body itself adds a bit of rollover crash structure, aerodynamic scuplting and, of course, a heaping helping of bad-assedness, but you could drive one that looks like this with little trouble.
But the MP4-12C isn't a body-on-frame vehicle either, not really. That's because the heart of the "frame" is a single-piece carbon-fiber monocoque (yellow) that weighs just 80 pounds. I guess we can call this body-on-monocoque construction. Whatever the term, it's put together very much like a prototype racecar you might see at Le Mans or Daytona.
The engine, transmission and rear suspension are carried by an aluminum trusswork (orange) that's bolted behind. This sort of trusswork isn't found in racing applications where the engine block itself is a so-called "stressed member" that doubles as the rear half on the frame. Here the engine is "unstressed", so the trusswork is needed to do exactly what it looks like it's doing.
Meanwhile, that aluminum beam up front is not much more than a deformable crash structure and a place to hang the nose.
Even though it's hard to see now, I can tell you from a test-sit in a full-bodied example that the monocoque provides plenty of space for occupants that stand well over 6 feet tall. In fact, McLaren tells me that 6-foot 7-inches was the upper end of their design envelope. Partial credit goes to the generously telescopic steering wheel that's supported by that magnesium dash support bracket.
Meanwhile, the gas tank sits beneath that shelf behind the seats.
Finally, some suspension bits to look at. To the surprise of no one, the McLaren's front suspension is comprised of double wishbones, a front-mounted steering rack and a coil-over shock absorber. And, of course, it's all made of "aluminium".
But this looks too clean and simple. Something's missing. What could it be?
I'll give you a few panels to figure it out.
In keeping with a construction theme we'll see repeated throughout, the MP4's upper control arm bushings have a tie-bar (yellow) that's bolted directly into bosses that are bonded into the side of the monocoque.
The shock absorbers have independent external adjustments (black) for compression and rebound damping force, with the uppermost one for compression and the lowermost for rebound. The electrical connectors at the ends (white) indicate that the adjustments are computer-controlled.
Here again, we can see how the upper shock tower bolts to another boss molded into the monocoque.
Are those hoses making you curious? Don't worry if the light bulb still hasn't flicked on.
Enough torture. The missing front suspension element is...a front stabilizer bar. The MP4-12C hasn't got one. Go ahead. Scroll back a couple of pictures and have another look. I'll wait.
What the McLaren has fitted instead is a complex series of tubes. These hoses (yellow) connect to the opposite side to form a hydraulic stabilizer bar that can be computer controlled. But to make it work they must cross over one another: the compression valve on this side connects to the rebound valve on the other side, and vice-versa.
Imagine you're in a sweeping bend. Naturally, the body wants to roll toward the outside, and this causes the outer shock to compress while the inner one grows. With this system, the pressure rise in the outer shock is re-routed across the car so it can repel the extension of the inner one, and vice-versa. But this only works if the hoses are "cross-wired", rebound to compression.
Here's another cool bit. There are valves, accumulators and electronics between the two interconnected hoses, and their presence allows the roll stiffness to be continuously variable, even during a single corner. For example: the system can be programmed to roll-in softly then firm-up as g-forces rise.
You can't do anything like that with a regular anti-roll bar, a simple bent piece of steel that tries to counteract body roll by simple torsion. Such a bar can only have one roll stiffness value. Even the adjustable ones have to be physically moved and "set" into one position.
Sebastian Loeb's all-conquering Citroen world-rally car once had a setup like this, and it was so effective it was later banned. More recently, a similar (but far less exquisite-looking) system is offered as an option in the new 2011 Infiniti QX-56 SUV. (We'll see more of that in an upcoming walkaround.)
Still not getting it? Here's the pair of crossover pipes (green) that plumb one side to the other. Both are connected via pressure lines to a control valve assembly (yellow) that sits on the floor of the front sub-frame. Those black dumbbell ends are the accumulators. One thing that's missing from this rolling chassis is a pair of matching pressure lines running up from the rear of the car.
Keep looking at the control valve assembly if you want, but this picture is all about the steering. The MP4-12C uses rack-and-pinion steering, and McLaren engineers told me they wanted to use hydraulic power steering for its superior feel. But electric power steering would have helped engine-bay packaging and parasitic power loss by eliminating the belt-driven pump, the belt hardware itself and the need for long hose runs.
To get both benefits, McLaren fitted this electric-driven hydraulic pump (black), which feeds the rack directly via short lines (yellow). This, then, is electro-hydraulic or electric-over-hydraulic power steering, and it's the best of both worlds.
Meanwhile, this small gap (green) shows that the front suspension and steering subframe is independent of that front crash structure.
In order to give the carbon monocoque the maximum possible stiffness despite door cutouts, clearances must be tight. They're so tight, in fact that there's no place for traditional door hinges. Instead, the door hinges attach higher-up (yellow). And that's why...
...the McLaren MP4-12C has "dihedral" scissor doors. Please don't call them Lambo doors.
The standard front brakes use 4-piston fixed calipers and two-piece front rotors made up of aluminum hubs and ventilated and cross-drilled cast-iron rotors. But there is an upgrade available, even though most owners won't need it. At this price range, it's a "want" thing.
I give you 6-piston fixed calipers and cross-drilled carbon-ceramic rotors. The little thingy above (yellow) is a brake cooling duct.
Moving to the rear, we can see another pair of wishbones and another coil-over shock. But wait? Is that (yellow) a stabilizer bar? No, it isn't.
See? Here on the right-rear there's nothing where the link on the other side attached to. This is something we've never seen before, so let's look at this again.
This is what they call a "z-bar" or "heave spring", and it's not something you see outside of high-level racing. And by high-level I mean high levels of aerodynamic downforce.
A stabilizer bar is u-shaped (albiet a wide U), so it does nothing when both wheels compress together. Its job is to resist body roll, to dampen the suspension from being fully independent, in effect, when the wheels are moving in opposite directions, such as they do in body roll.
Because one leg goes forward and the other aft, a z-bar (or heave spring) is exactly the opposite animal. In corners, it does nothing to inhibit roll. If one wheel hits a bump, it's not going to put up much of a fight. But when both wheels compress together, as they might when a huge wing is creating a ton of downforce, the z-bar becomes a spring that counteracts that force. This allows the coil springs at the wheels to be relatively soft for good mechanical grip and drivable comfort.
You don't see this often because not many cars make enough downforce, either because they don't really have a big rear diffuser or wing, or because they don't go fast enough. The MP4-12C goes fast enough, and it's got a real, functional diffuser. The rear downforce is significant.
Like we saw up front, tie-bars (green) hold the rear control arms in place. The toe-link (yellow) pivots on an inner ball-and-socket joint.
No, that's still not a stabilizer bar. Sorry.
In order to clear a path for the shock, the aluminum upper control arm is L-shaped instead of A-shaped.
Like the front, the "stabilizer bar" is really just a pair of hoses.
Don't be distracted by the pretty exhaust system that exits high so the rear diffuser can make gobs of rear downforce. Because this is a suspension walkaround, the thing to look at here is the pair of hoses that cross-links the shocks.
Maybe this stretches the definition of suspension, but the engine is "suspended" in the rear frame by these (yellow) links. Fuel is suspended in this well-protected tank (black). That green thing? Oh, that's nothing much. Just one of two turbochargers, that's all.
The back half of the engine and transaxle is suspended from this frame crossmember.
Like the front, braking duties are handled by a 4-piston fixed caliper and two-piece cross-drilled and ventilated cast-iron rotors that ride on aluminum hubs. Unlike the front, there's a smaller brake caliper strictly for parking brake duty.
Upgraded rear brakes consist of carbon-ceramic rotors and silvery calipers. I prefer to use the term black chrome.
If we play our cards right, we may get a chance to put one of these on the track fairly soon. I'm crossing my fingers and toes. I could use your help.
Photos by Kurt Niebuhr. Arrows, as usual, by me.
konocar400h says:
08:26 PM, 09/ 6/10
Wow, beautiful. That cars innards are gorgeous and I'll be interested to see how all the tech works in the real world. This was one of the best writeup's I've read.
Also, I've never seen a brake system setup like that with the two calipers. Is that also a new innovation or did they run out of space to put the e-brake drum inside the disc?
mpowerf1 says:
09:37 PM, 09/ 6/10
Awesome stuff. Post of the year, in my opinion. Wouldn't find this anywhere else.
s70driver says:
09:38 PM, 09/ 6/10
The dodge viper also has the dual caliper setup for its rear wheels.
maxedoutmax says:
10:25 PM, 09/ 6/10
The 2nd caliper is just the parking brake...
turtle99 says:
03:10 AM, 09/ 7/10
Thanks for the highly educational stuff.
So my question is how advanced Mclaren's technology is compared to MB, BMW, AUDI and Toyota/Lexus?
Do they produce their own engines and transmissions?
kk5255 says:
04:03 AM, 09/ 7/10
The MP4-12C is exquisitely manufactured. engineering art. mind boggling attention to detail. i can just feast my eyes looking at the fine cast finish and welding joints. also, first time knowing the existence of "hydraulic stabilizer bars'!! :p.
this article teached me a lesson: do not judge a car by its skin!!
moreau says:
07:00 AM, 09/ 7/10
Neat, but student Formula and Baja SAE teams have been doing hydraulic sway bars for years =p
Other than that, it's just double wishbone front, double wishbone + toe link in the back. Nothing magical about it, although that is generally the best possible design. Suspension is just simple geometry anyways, the fine tuning of it is the real pain.
I'm more interested in the carbon fiber, or why they didn't use more of it. They substituted the simplest and lightest portion of the car with... the lightest stuff they have. I can understand the front aluminum substructure, as it probably is necessary for crash regulations, but why make use of it instead of aluminum in the engine bay? They've already opened the can of worms of interfacing carbon fiber components with other structures, although they cleverly did not mount the front suspension to the carbon fiber, so why stop there?
The only way that center carbon fiber portion makes sense is for a convertible version. Bragging rights probably also factor in. Also, extremely high stiffness isn't important for dynamic performance (4000 lbs/deg is fine, but most cars are over 10,000). The main reason automotive engineers make a stiffer car is to make it quieter, not a better performer. And if McLaren really wanted it stiff, they would have a full carbon fiber roof too.
I'm much more interested in the drivetrain and engine.
lemiet says:
08:39 AM, 09/ 7/10
Totally awesome review. Insideline is coming back to it's original roots. Wonderful setup by McLaren as well, the suspension is an interesting layout not found done this elegantly by most.
@Moreau: I, like you, would love to see a review like this dedicated to the drive/powertrain.
santiagofdz says:
11:59 AM, 09/ 7/10
What a post! Reading this was an unexpected present! Thanks for making this happen guys. This naked chassis could very well reside in several modern art museums and not look out of place, the attention to detail is impressive.
@Dan Correct me if I'm wrong but does the the Z-bar do the same job as a 3rd damper would do in an F1 car?
And speaking of Mclaren and dampers, I'd assume the ones used on this car also have the "inerter" damper design? That made some news when it was uncovered by rival F1 teams.
mike_honcho says:
02:40 PM, 09/ 7/10
Thanks again Dan, these walk arounds have been spectacular. I'm glad that I got that the stabilizer bar was missing from the first few pics, and I have you to thank for that.
alex38 says:
05:52 PM, 09/ 7/10
Slick reporting here with great pics and explanation. Very interesting. Thanks
actualsize says:
06:22 PM, 09/ 7/10
@alex38: Thanks for the reminder. I cannot take credit for these "great pics", although the arrows are mine. I usually shoot my own walkaround shots, but indoor lighting is not my friend, so I called upon Kurt Niebuhr, one of our staff pro shooters, to help me out. A side benefit of this strategy was this: it freed my hands up for an iced tea while I chatted with the McLaren rep.
cw910 says:
09:22 PM, 09/ 7/10
Fantastic post.
mixim says:
01:22 AM, 09/ 8/10
Dan, all of these suspension walk-arounds have been amazing, thank you for these! Nowhere else can I find detailed reports about the components that interest me the most. And of course, when we're talking about a MP4-12C suspension, the awsomeness-factor skyrockets to new levels =)
cornflakes99 says:
11:10 AM, 09/ 8/10
@ moreau
1. Using carbon fiber around the engine bay cause's problems with heat transfer, carbon fiber is great but it doesn't like heat, most carbon fiber based cars use formula one principals ie. the engine being a fully stressed member of the chassis, this has problems when bolting monoque & engine together ie. massive vibrations from the engine sent into the passenger compartment (think Ferrari F50) and is very difficult & expensive to engineer a solution (think McLaren F1), the most efficient & cost effective solution is to use a cradle and bolt the drivetrain to that.
oh and about the suspension if you look at the pictures you will see the front top wishbone is bolted directly to the carbon tub.
2. "extremely high stiffness isn't important for dynamic performance"....er....really! say that to any engineer and they will roll around laughing, the monoque isn't "simplest and lightest portion of the car" as you put it, but one of the most complex & important parts, it is the backbone to which the rest of the car functions, the body in white of the Merc SLS AMG is about 440lbs (200kg despite being made of aluminum) the engine between 440-550lbs (200-250kg), the reason for the weight of the chassis is to make it flex as little as possible so the suspension geometry is as accurate as can be, McLaren has archived infinitely higher accuracy & less flex with a body that is only 176lbs (80kg).
The reason manufactures put a ton of strengthen beams under converterables (think Saab) isn't to keep them quite, it's to stop them flexing, something this McLaren will not need!
cardesigner82 says:
04:05 PM, 09/ 8/10
Nice read Dan. I'd like to reiterate that I'd STILL rather have a MP4-12C than a Ferrari 458 Italia
peloton25 says:
06:10 PM, 09/ 8/10
Small error in the article:
"That's because the heart of the "frame" is a single-piece carbon-fiber monocoque (yellow) that weighs just 80 pounds."
cornflakes99 got it right when he said 80kg or 176lbs.
Otherwise a great read - thanks!!
mrjost55 says:
08:28 PM, 09/ 8/10
Thank you for the detailed explanations of every bit. And I'm surprised you got that close with the camera. Enjoyed the whole read.
actualsize says:
07:43 AM, 09/ 9/10
Drat! That kilogram/pound thing got me again!
kevinlch says:
12:00 PM, 09/ 9/10
such a pleasure to see this piece of art, good article!
jerryc101 says:
11:09 PM, 09/10/10
Lots 'o cool stuff. Time was, the McLaren team used the spare garage at the racecar shop I go'for'd at, and they wow'ed us with their very early use of carbon fiber.
The Zbar... yes, quite a concept. Worked well on my 68 swing axle Karmann Ghia... I think they came on the 67 also. They were to compensate for excessive 'downforce', which translated to 'people in the back' *grin*
actualsize says:
03:16 PM, 09/12/10
I was wondering when someone was going to bring up ancient Beetle tech. I've seen them on Formula Vee formula racers that are based on old Beetle components - no downforce there either, but the z-bar was a space efficient way to spring the rear axle while keeping the rear of the car very narrow.
actualsize says:
03:20 PM, 09/12/10
...and in your case to compensate for the terrible weight distribution caused by the engine hanging off the back of the car, especially, as you say, with "volks" riding in the backseat.
sherief says:
09:34 AM, 09/13/10
I never thought I could be so impressed with a steering rack design.
topherbd16 says:
11:20 AM, 09/14/10
Does anyone know the location of this display? I assume this is a special invite only by McClaren to see this.
charlesncharge says:
04:29 PM, 09/15/10
Dan,
Didn't the Audi RS4, and a version of the Toyota 4Runner have some type of system the linked the dampers diagonally with one another in an effort to reduce body roll? Although both of these vehicles were still equipped with conventional stabilizer bars. I believe the system Toyota used was developed in conjunction with Yamaha (maybe Audi, too?).
Also, did you ever happen to do a suspension walk-around on a NISMO 350Z, and possibly explained what those cross dampers did the were attached to front/rear frame members, which incidentally, also manufactured by Yamaha.
Great article, by the way - thank you!
actualsize says:
06:46 AM, 09/22/10
The most recent 4Runner and Land Cruiser (and LX460/470) have a different sort of (optional) system called KDSS. Unlike the McLaren and QX56, they feature great big stabilizer bars -- much bigger ones than you'd normally put on an off-road vehicle. But there is a hydraulic component that automatically disconnects the bars when the system detects the front and rear axles are transitioning into "opposite phase" or frame-twist mode.
While the McLaren can vary the roll stiffness over a wide range and even during a single body roll event, KDSS is an either-or proposition.There are no shades of gray in between the limits. Max roll stiffness in corners, no roll stiffness at all when boulder hopping. It's the best of both worlds for an off-roader. I have 4Runner pictures, but they're not very good. I will try to do something with them soon, however.
nachof says:
02:50 PM, 11/27/10
Awesome detail. Great pictures. Arrows pretty good too.
Suspension includes Monroe CES shock absorbers and Kinetic system (yes, banned from Paris-Dakar, it was too effective). So good technology is penalized.