We thrashed the new 2012 Porsche 911 Carrera S at the track and then we tossed it at some curvaceous mountain roads. Now it's time to give the 911 a much-needed rest and hoist it up on our new Rotary two-post lift for a clear look at the suspension that does the business.
This new 911 is in fact a 991 in the language of Porsche engineering, which is why the 991 prefix appears on the various components we'll soon see. You may also notice a bit of grit and grime under there because the roads were wet much of the time we had it -- except at the track, thank goodness.
Let's get on with it. Here's the 411 on the new 911 suspension.
From here we see what looks like the standard 911 setup: humungous brakes and a MacPherson strut suspension.
A forged aluminum front knuckle (orange) grasps the bottom of the coil-over strut. Like other 911s before it, the 991's steering (yellow) meets it up ahead of the front axle's centerline.
It's electric power steering this time out, but the components are buried beneath covers we don't dare remove. Steering feel earned mixed reviews, but steering accuracy and direct response are as good or better than what we've found in the model it replaces.
The lower control arm is partially hidden by a convoluted bit of ductwork that sends cooling, soothing relief to the brakes.
A lateral link and a tension link come together in a bolted joint to make that lower control arm. Forged aluminum, of course.
As we've seen before, the front stabilizer bar loops over the top of the lower control arm to meet up with the stabilizer link (yellow,) but here that link is something very special, indeed.
Meanwhile, the damper within the strut housing is fitted with PASM (Porsche Active Stability Management,) a continuously variable damping system with two driver-selectable operating ranges, Normal and Sport.
The stabilizer bar link (green) is hydraulic, as is its opposite number on the other side of the car. A central computer looks at body height sensors, steering angle and a host of other factors to determine how to make them behave.
On straight roads they can go limp to essentially remove the stabilizer bar from the picture for a smooth ride. In corners they can be made to "overdrive" what the stabilizer bar could otherwise do on its own to utterly eliminate body roll. Or the computer can dial in any amount of roll stiffness in between, and it can change its mind in real time as road conditions or driver inputs fluctuate.
Porsche calls this Porsche Dynamic Chassis Control (PDCC) and it's the first time they've fit it to a 911-series vehicle. Whatever you call it, it flat works. This very car pulled 1.04 g on our skidpad, and some of the credit has to be put down to the way this system can make use of all four tires instead of leaning heavily on the outside ones.
You could theoretically achieve the same skidpad prowess with a pair of very big stabilizer bars, but then the car would ride like Grade A dog doo. Conversely, a hydraulic anti-roll system such as this doesn't need a physical stabilizer in between the left and right struts at all, but in that case there'd be no fail-safe if the system developed a fault.
As for those looming red brakes, the massive 6-piston Brembo calipers have a pair of fixed bridges (yellow) for maximum caliper stiffness. This means the calipers have to come off when it's time to change the brake pads which, incidentally, are equipped with electronic pad wear sensors.
And now we know what these big hoses (green) are for: they feed hydraulic fluid to the PDCC active stabilizer bar struts.
This sensor, along with three more at the other suspension corners, measures the position of the lower control arm to deduce the position of the tire.
The PDCC system compares the readings to that generated on the other side to measure body roll, and the PASM active damping system uses them to understand the motions of the wheels in order to determine the amount of damping required, be it for ride, cornering, dive/squat, etc. It's likely the headlights use 'em too for auto-leveling.
Here's another look at the 6-piston Brembo calipers. The ventilated and drilled rotors they grip are 13.4 inches in diameter and 1.3 inches thick. This car stopped from 60 mph in 102 feet.
Out back we find a new beautiful-looking multilink suspension.
A sea of forged aluminum surrounds a coil-over monotube shock that naturally contains the same PASM damping internals found up front.
Our new Rotary lift makes it easy to get directly under the car to get a clear view of the 991's two lower links.
The rear shock (and the spring that surrounds it) attaches directly to the rear knuckle for a 1-to-1 motion ratio. Such a ratio demands a long shock absorber, so the lower link employs a fork shape to allow the shock to sit low in the car.
Camber adjustments are made via an eccentric cam on this link's inner end.
Think of the rearmost pair of upper links (yellow) as an approximation of an upper control arm and the forward link (green) as a toe link. Close as they are to the hot brake rotor, their outboard pivot bushings must be made of hardy stuff.
The top of the rear stabilizer bar link (white) is just barely in view, but the fact that it's mounted directly to the rear knuckle means it operates at a 1-to-1 motion ratio.
Our trio of upper links attaches to a forged aluminum subframe (yellow) that contains a notch (black) for an eccentric adjusting cam for the toe link.
Just like the front, our 991 911's rear stabilizer links are hydraulically controlled by the PDCC system.
Also like the front, rear height sensors on each side relay the position of the rear suspension to the car's central brain, which in turn shares this data with numerous systems.
The lightening holes in the rear knuckle allow us to see how the electric parking brake worms itself into the hat section of the rotor, where a drum parking brake lays hidden.
As for the real rear brakes, they're made up of 4-piston fixed-bridge fixed calipers and fully ventilated rotors measuring 13-by-1.1 inches.
A small NACA duct admits air into ductwork that sends air to the rear calipers.
Here's another view of the same ductwork.
All of this rides on massive 20-inch wheels, another 911 first. The fronts measure 20-by-8.5 and are wrapped with 245/35ZR20 rubber, while the rears consist of 20-by-11 wheels and 295/30ZR20 tires. I'd like to tell you how much they weigh all mounted up, but I have not yet equipped our new shop with a suitable scale.
For what it's worth, Porsche claims that the wheels are lighter (than what and by how much they don't say) thanks to a flow-forming process. They also claim the tires have 7 percent less rolling resistance (than last year, presumably) which makes the 1.04 g skidpad number we measured all the more amazing.
csubowtie says:
04:01 PM, 11/28/11
I am surprised that the front suspension is just a Macpherson. I expected something fancier. I'm not sure how I feel about the stabilizer thing. When I was in college, one of the problems we were focusing on for our FSAE car was how to seperate roll damping from bump damping. And I suppose this system does that, and adjusts roll stiffness on the fly as well, AND can physically overdrive one side. That's cool stuff. On the other hand, it seems extremely complex and heavy. Why not just put a computer controlled hydraulic cylinder at each wheel and let the computer determine where to position each tire?
saynotogm says:
05:07 PM, 11/28/11
MacPherson strut? Wow....
chikoo says:
05:48 PM, 11/28/11
Porsche Front - McPherson
BMW Front - McPherson
Lexus IS Front - Double Wishbone
Mazda6 Front - Double Wishbone
Wow.....
wjtinatl says:
06:13 PM, 11/28/11
WOW. Ford Motor Company didn't pay Earle MacPherson enough money. No matter how much he made, it wasn't enough.
actualsize says:
06:26 PM, 11/28/11
Most of the bad things we associate with MacPherson struts have to do with front-drive econoboxes. Done right, they work well. Right includes high-quality dampers, sufficient caster and camber, low unsprung weight and front-mounted steering -- all of which are found here. Plenty of sporty RWD cars make them work.
zr1man says:
09:36 PM, 11/28/11
Well, supercar suspension being wasted on non-supercar performance. 13.0 seconds in the 1/4 mile and 0-60 in 4.6 seconds is not even good sports car performance, much less supercar performance. I'll pass on this one.
Be Proud. Buy American.
337 says:
02:57 AM, 11/29/11
This is not a supercar. You have no idea what you are talking about.
lostboyz says:
03:59 AM, 11/29/11
For the love of god can we get rid of people like zr1man. The comments sections are slowly turning into autoblog that's up to 80% fanboys and spammers. It's not like we don't know what he is going to say. Ford focus review -> my zr1 is faster, chevy runs deep. Camry review -> my zr1 is faster, be proud, buy american. See, we don't need him.
I'm going to miss (and I'm sure your neighbors are too) the driveway walk arounds, but that lift is a hell of a thing. Thanks for the look around.
scottyscooter says:
04:14 AM, 11/29/11
The hydraulic end link just blew my mind!
noburgers says:
05:27 AM, 11/29/11
Love the lift. That's a lot of forged aluminum! By the time I reached the end photos I shuddered over how much it's going to cost to make repairs to any of these sensors/hoses/shiny bits.
Speaking of blowing hot air, the underside airflow management is also impressive.
Photo 4--someone already scraped the underside, probably on a driveway apron.
Question for Dan--since you do all of these suspension walkarounds, do you use a torque wrench to set the lug nuts back to specs?
duck87 says:
06:02 AM, 11/29/11
My FSAE team did the only logical thing: We simply didn't have any antiroll bars. They were meant to be used as "trim" devices for fine-tuning spring rates, but we raced on only one autoX circuit, where they were pretty much useless. Since they reduce mechanical grip, we went with stiffer springs and the bars were taken out.
The problem with having an individual cylinder on each side is as the author said: in the event of a failure, you suddenly have no antiroll bars. A physical connection means that even if things fail (i.e. in the middle of a turn), you aren't suddenly screwed over and can still drive the car safely. This antiroll system reminds me a lot of the antiroll system in the McLaren MP4-12C, except that one is the inevitably conclusion to this hybrid system Porsche is using (i.e. the McLaren system is fully electrohydraulic and variable).
As for the Mac strut setup, as someone else said, this kind of setup has been used in 3-series and 911s front suspension for decades. True, they don't have much in the way of desirable camber gain and can't locate the wheels as well as double wishbones throughout suspension travel, but it seems to be less of a problem in a properly sorted RWD car... as long as the rear suspension is properly sorted out.
notzr1man says:
06:29 AM, 11/29/11
Impressive engineering on a fantastic car.
Be Proud. Buy American [cars manufactured in Mexico].
prefcustomer says:
06:37 AM, 11/29/11
Too bad about the fixed bridge calipers. One of my favorite things about the current gen cars is how easy it is to swap pads for the track; literally 10 minutes per wheel, and most of that is getting the car jacked up and the wheels off.
spqr309 says:
07:19 AM, 11/29/11
Another reason why I love the walk around. Amazing how they are able to make the McPherson to work so well. Engineering at it's best. Air management for cooling done well. I can not agree more with lostboyz, can we please move on already!! Duck87 great comment. Just learned something.
truecarfan says:
07:31 AM, 11/29/11
Now this is what I call automotive journalism!!! Thanks for this!
plateface says:
08:00 AM, 11/29/11
It would be more awesome to have video footage of the suspension in action to go along with these walkarounds.
cjasis says:
08:21 AM, 11/29/11
Absolutely love these suspension walk arounds. Very interesting and informative.
To those clamoring about the MacPherson struts at the front... give it a rest. You don't have to be fancy or complicated to work. The fact is, as Inside Line has already pointed out, this car rides nice and smooth when you want it too but corners like a banshee when you want it to. Added cost and complexity gets you what exactly?
And ZR-1 man... we know... we've heard your diatribe a bazillion times. Everything not badged Corvette sucks. Change the record.
skidrive9 says:
08:22 AM, 11/29/11
Nice job, i like the lift you have there haha. i like the idea of doing a video walkaround like plateface said.
AND
***Insideline, can you PLEASE get rid of zr1man, he is a troll that hates on any car that isn't made by chevy. I have not seen a single post by him that hasn't tried to provoke some kind or argument yet!
jrt600 says:
08:29 AM, 11/29/11
+1 on getting rid of zr1man - his mindless ramblings are getting quite old and repetitive.
omairkhanzada says:
09:02 AM, 11/29/11
LOL @ the hate for ZR1 man. I'm not condoning what he says in every post is correct. He, just like you, is entitled to his own opinion. Do not pay mind to the nonsense he posts. And also to the guy "notZR1man", by making such a name, you only empower him more by bringing more attention to him, that's all he wants.
I am in love with this car. I agree however that when a MacPherson is done right it can do wonders. I love how BMW, Porsche, and Mercedes have their own anti roll system now. I personally still like how BMW's ARS works with the hydraulics being in the middle of the roll bar. I guess this system allows you to personally cater to the stiffness of each wheel. Great car, great design.
yellowmiata says:
09:31 AM, 11/29/11
@ Dan / Acutalsize
I appreciate your note regarding MacPherson struts up front, and I've poured through the internet looking for info and opinions regarding MacPherson vs double-wishbone. As noted by chickoo, some very sport-oriented cars use MacPherson, yet racecars tend toward double-wishbone.
Given that you have provided me/us with excellent suspension walk-arounds and have the capability of translating complex topics into legible and coherent thoughts, might you shed some light on the benefits and drawbacks of each? Perhaps in an article or in this blog?
BTW - great writeup here, I enjoyed your detail.
Kevin
flwind says:
09:31 AM, 11/29/11
Kudos to IL for finally using a proper lift on these high dollar vehicles.
bodyblue says:
09:46 AM, 11/29/11
Zr1man is bad enough but then so is notzr1man.....no way either one of them is over 15 years old. Like it or not zr1man does not violate IL rules....he just is a punk at a computer. Ignore him and his alter ego.
kosmo69 says:
11:59 AM, 11/29/11
Forged AL is nice. MOst are cast.
The brakes calipers needing to be removed to access the pads is silly. The 997 pad change is sooo easy.
ZR1man I love how you drive a car whose suspension cant handle the engines power.
I think "ZR1Douche" is a more appropriate handle.
rod_stewart says:
12:50 PM, 11/29/11
@ Dan Edmunds
Awesome job as usual but I have a question....
You say "steering accuracy and direct response are as good or better than what we've found in the model it replaces."
But in the Track notes on the 911 review it says "Quick turn-in but a small delay in yaw reaction. Tracks very true to steering input but requires a little patience for the chassis to catch up."
That doesnt sound "as good or better" then the 997, does it? Just curious. Thanks for the great work with these walkaroudns!!
-Rod
kosmo69 says:
01:19 PM, 11/29/11
zr1man should change his handle to zr1doosh.
duck87 says:
01:30 PM, 11/29/11
@rod_stewart: There's a difference between "steering" and "chassis/suspension movements", and that's what the author is talking about. The car still steers in the direction you want to go, but the car takes a second for the rear to follow the front.
It also tells you that such things are subjective. I think it's pretty crazy for anybody to bash the car for its steering feel when they haven't driven it- because such a thing has a high level of subjectivity (and how "good" steering is depends on which car you came from last).
sherief says:
01:45 PM, 11/29/11
MacPherson struts due to their simlicity take up little space, are extremely light, and allow lots of wheel travel. Considering how much of the 911's weight is rear biased, it's pretty difficult to notice the MacPherson strut suspension's drawbacks.
As for BMW...I assume they soldier on with the MacPherson layout to maximize space under the hood, a side effect of their preference for using engines that don't have compact layouts.
church123 says:
02:18 PM, 11/29/11
+1 sherief
Under acceleration there is so little loading on a 911's front tires it's almost silly. Of course, that's why you have to make sure you get the car slowed down properly and turned before getting on the gas, but if you do, you'll amazing traction on the way out. It's also one of the few cars that will reliably power understeer if driven incorrectly. It's one of the special charms of driving a 911 that makes people love them so.
actualsize says:
03:06 PM, 11/29/11
@rod_stewart: That comment came from the slalom test, which isn't necessarily a real world replica of a typical corner. It's like stringing 3 or 4 super tight racetrack chicanes end-to-end. You learn interesting things there, but its all exaggerated. Out on the open road things happen in a more deliberate fashion, even when you're pushing.
rod_stewart says:
04:01 AM, 11/30/11
Thanks @actualsize, that makes some sense.
Still you would HOPE that a $100k Porsche 911 could do it all! Overengineered, no compromises and all that.
I just dont remember the 997 getting negative slalom comments like this. Having to make excuses for a 911's lack of responsiveness i.e. "don't worry, you won't notice on the open road"......Ferry Porsche is turning in his grave.
-Rod
mckman says:
04:44 AM, 11/30/11
Don't think anyone mentioned this, but another plus of retaining the sway bar is that the hydraulic system can be smaller and lighter. The hydraulic system only needs to add and subtract from the stock rate of the sway bar instead of having to generate all of the additional roll stiffness itself. Limits the system somewhat compared to what the McLaren MP4 can do, but in practice it probably doesn't matter too much.
zr1man says:
09:19 PM, 11/30/11
FYI, Here is a link to a video made by Motor Trend that shows the 2011 ZR1 knock out the 2011 porsche 911 turbo.
Http://www.aol.com/video/2011-corvette-zr1-vs-2011-911-turbo-comparison/517202519/
No tears please.
Vettes Rule
actualsize says:
10:37 PM, 11/30/11
@rod_stewart: I get what you're saying. But the real test will be lapping on a racetrack -- that's much more to the point than wriggling past a few cones. We haven't done that with the new 911 just yet, but we will once we get more time with one.
scott230 says:
09:02 AM, 12/ 1/11
It is interesting to compare this suspension to the one on the Zo6 corvette. I have had 911's in the past and the reliability/handling are awesome. It is nice to only visit your dealership once a year or every 15,000 miles to change the oil as routine maintenance. The brakes are also phenomenal as I guess German standard state cars must not exhibit brake fade ofter 25 consecutive emergency braking.
ampim says:
01:31 PM, 12/ 1/11
@duck87 says
Like you said, the major drawback of a strut is the crappy camber gain. But since the 911 doesn't have an engine up front to package around, it can lean its struts in more and get as good of a camber gain as a double wishbone.
arfdog3 says:
05:00 PM, 12/ 1/11
McPherson Strut
- no camber gain thru travel (good thing)
- packages better
- simpler
- cheaper
- better control of camber/caster
- hence, more direct steering response on a road car (race cars can use solid joints on their upper A-arms, road cars can't due to NVH transmittance)
Double A-arm (wishbone)
- better overall control of suspension kinematic motion
- better camber/caster control (solid joints)
- worse camber/caster control (isolated joints)
- packages poorly
- expensive
duck87 says:
07:44 AM, 12/ 2/11
@arfdog3: I'd argue that the lack of camber gain through travel is NOT a good thing. Camber gain through travel is what allows you to tune the suspension for minimal camber in a straight line (i.e. it will track straight with minimal camber thrust), while allowing negative camber in a corner where you want it. A macstrut has minimal camber change through most of its travel, but the more pressing concern is that at the limits of a Macstrut suspension, the tires tilt towards POSITIVE camber, destroying handling at the limits.
More accurately, a DWS allows you to control the amount of camber gain you want, very precisely. You can still have zero camber gain if you want (by making the upper and lower control arms the same length).
@arfdog: You have to consider the kingpin inclination as well making those changes. Again, it's all about compromises, and a Macstrut has more compromises in its design. I'm not saying it's bad at all (far from it), but it's just something to consider.
@actualsize: I'm not sure where else to post this so I'm hoping you can help me. A lot of people are starting to claim that front vs. rear steer offers more "feel". Can you explain to me why? From my understanding back in Formula SAE, it was mostly for packaging considerations, and geometrically the two are quite similar when you work it out (except for which links are in tension and which are in compression).
lzks says:
04:27 PM, 12/ 8/11
I still cannot fathom the electric steering being better than the previous 911's with hydraulic. I better testdrive one, if any dealers let me;; "Hi, I'm here to testdrive your new 911." "How much do you make?" "Uh..."
mazdized says:
09:58 AM, 05/ 6/12
McPherson has better feed back and room to correct, double wish bone handle great and may have higher lateral g but is snappy and on the edge. Thats why you see many FD RX7 and C5 and C6 Vettes get smashed on 3 corners when the drivers think they have more skills then brains but the reality is they have no idea how to handle a snappy car. New cars are not meant for you to work on it in your garage with a floor jack and hand tools so they have no reason to make it repair friendly, if anything it should be unfriendly so you can pay the dealer. Dont thing the rear sway bar link is 1 to 1 because the mounting pivot is not lined up with the outer 2 upper link ball joints so may have some movement reduction there compared to hub movement. Sway bar is useless you just need stiff springs.... I agree but no one would buy a street car that rides like a ASE project mobile right? so they have to put all that stuff on it so it can have or try to have the best of both worlds, besides I am sure a link is at least $700 from dealer. As for ZR1.... in case you have not noticed there are other performance in the world other then straight line acceleration. I am sure ZR1 is great so may be you should bring out the handling performance number of the ZR1 next time you post. Buy America.... you mean Mexican and Canadian?
swift996 says:
06:41 AM, 05/24/12
I've owned 14 cars with multiple set ups. While I love the idea of double wishbone suspension all around which was on several cars I've owned, the 911 was the best handling car I've owned. They have a track record of making some of the finest performing street cars and dominating motorsports. Don't hate on Porsche or the 911, it just makes you look stupid.