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Smart Air Suspension VS Coil over Spring

Discussion in 'Model S: Driving Dynamics' started by ZBayChris, Mar 14, 2014.

  1. ZBayChris

    ZBayChris Member

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    We have placed our deposit a few days ago and have one more week to finalize the car. I have only driven test cars with the Air Suspension and we love the ride and handling. We are not sure if that is mainly due to the SAS or Model S in general. When I saw the relatively little up and down range of the SAS I decided to take it off of the deposited order. Now I am wondering if that was a mistake. I would like opinions of those of you would have driven both configurations. I am not asking whether it is worth it to get the SAS because I know that is very subjective. But my wife and I would love to know how the two types of suspension act/feel in everyday driving. Thanks to everyone who contributes to TMC. I think we can all attest to how much these forums have increased our ability to make wise decisions concerning this great car.
     
  2. gg_got_a_tesla

    gg_got_a_tesla Model S: VIN P65513, Model 3 Res Holder

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    I have SAS in my car but, I did drive a P85 loaner with standard suspension a couple of weeks ago.

    Apart from the convenience of being able to raise the SAS to higher settings to clear curbs/parking-stops/steep-driveways (including my own for which I have to go to the High setting everytime I back into my garage), SAS may score over standard in road noise. I found the loaner car much louder in the cabin than my own. A couple of other factors may have contributed to that though - 21" wheels and pano roof both of which my car doesn't have.
     
  3. Merrill

    Merrill Active Member

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    I also have the smart suspension, well not so smart at this time but soon to be smart again. I have the pano and 21's and love the suspension, I live on a country road which is a bit bumpy and the car handles and rides very smoothly. Never driven in a coil spring version so cannot compare. I do know that this ride is far better than my Jaguar or Mercedes, both of those feel like a bucket of bolts compared to the Model S. If I had to do it again would definitely go with the smart suspension, I really like that it lowers at highway speeds.
     
  4. mknox

    mknox Well-Known Member

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    Ummm... maybe you're not aware of this.
     
  5. Chipper

    Chipper Active Member

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    I test drove a coil suspension but purchased a SAS equipped car. (It arrived to me un"Smart" but that's another topic well documented elsewhere.) I have not ever regretted the choice. The auto-leveling and slightly improved aerodynamics as well as the option to raise it going over speed bumps and into steeper driveways just made it seem like the right thing to do. Get what is best for you, but my recommendation would be to include SAS.
     
  6. ZBayChris

    ZBayChris Member

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    I definitely think the 21" wheels contributed to some of the noise because our first test drive was in an 85+ with 21's and it was noisier than a one day test loaner that was an 85 w/19" wheels. Because of the harsh winter we have had here on Long Island, there are a lot of pot holes and rough road surfaces. When we had the loaner for an entire day, we all commented on how well the car, which had SAS, handled the bumpy roads and how relatively quiet the ride was. I don't know if that is attributable to the SAS, the 19" tires or the construction of the car in general. That is kind of our dilemma.
     
  7. Chipper

    Chipper Active Member

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    Hey mknox, it still lowers at highway speeds...as long as your highway speeds are around 100 MPH!! :tongue:
     
  8. Merrill

    Merrill Active Member

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    Just being optimistic!!!!!

    - - - Updated - - -

    FYI when I purchased my car I chose the 19's for all the reasons you talk about. I must preface my comments by saying I live in California so weather is not a problem. After driving the car for 6 months I just could not get out of my mind how nice the 21's looked. Decided to switch and in the beginning I notice a slight difference in ride and noise, but after driving for a couple of months with the 21's I barely notice any change. I like the air suspension, but to each his/her own.
     
  9. passion4audio

    passion4audio member

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    I'm probably in the minority here, but was not impressed with the floaty/disconnected from the road feeling the air suspension gave me. Yes, it is more comfortable over bumps. Yes, you have the ability to raise the car - and it will lower just a touch more. The "deal killer" for me was that the air seems to come between the driver and the road. If you are coming from a Porsche, or other car where the suspension has been performance tuned… you will know what I'm talking about.

    Review Lolochampcar's posts - as he has probably contributed the most to this topic.

    If you're coming from a Cadillac, Lexus (or similar) then you will think the air-equipped MS is stellar in the handling department.

    I'm guessing that in the coming months or years you will see a variety of aftermarket offerings to further improve the non-air suspension.

    There are a few other things to think about as well:

    1. WHEN the air suspension stops working - and it will eventually - it will be extraordinarily expensive to fix.

    2. I'm guessing that air-equipped vehicles with higher mileage may be more difficult to sell because of this.

    Whichever version you choose, however, the MS is an amazing car. It's just a matter of personal preference as to which suspension option you prefer.
     
  10. beck.christopher

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    During both of my test drives I drove a car with air suspension. This was my first time driving a car with air suspension and I did not like the disconnected feel. I did like the ability to raise and lower the car as needed however I chose to stick with the coils for the price and the connected feel with the road.
     
  11. ZBayChris

    ZBayChris Member

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    Thanks for your input. We are coming off of cars very dissimilar to a Porsche. :smile: A Honda Accord EX and Grand Caravan EX. We plan on keeping both for the near term. I thought I had read on other threads that Air Suspension, in general, has gotten more and more reliable, in cars, over the years.
     
  12. mknox

    mknox Well-Known Member

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    Well, yeah, but I would probably characterize that as "autobahn speeds" :tongue::tongue:
     
  13. Zextraterrestrial

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    I feel the opposite. I hated the floatyness of the coil loaner vs my air susp. same 21" wheels but the coils have an extra bounce when you go over a bump or frop off of a bridge deck taper. My wife thought the same thing. she didn't drive the loaner though, just passenger ( she was getting carsick in the loaner just driving around town!)
     
  14. Gizmotoy

    Gizmotoy Active Member

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    #14 Gizmotoy, Mar 14, 2014
    Last edited: Mar 14, 2014
    Any coil suspension car that feels like its bouncing has a problem, likely with its dampers. A properly-damped car will have no rebound, as the bounce creates lift on the wheels, reducing traction and creates a very dangerous situation. Considering, what 98%+ of all cars on the road have spring-based suspensions, if you got in one that was bad enough to make you carsick, clearly there was something wrong with it.

    The reason the air suspension's ride is more comfortable is that it is slower through the transitions, a sensation when taken to extremes is usually referred to as 'floating.' A car with a coil suspension transitions faster, and when that transition is a bump or pothole, it results in a more sharp sensation than in a car with an air suspension. Taken to extremes, these fast transitions are usually referred to as being 'harsh' or 'punishing.'

    Further, damaged dampers are a common failure case for a car with a coil suspension, which involves allowing the spring to over-correct after a transition. In this case the car bounces subtly. Sometimes you'll see a car on the highway that's bouncing noticeably on a flat surface. This is the extreme damper failure case, and is very dangerous. Stay far away from those vehicles.

    It's also important to note that the above is from the perspective of someone in the passenger compartment. A passenger compartment resting on an air suspension may react more slowly relative to its coil counterpart, but that doesn't mean the wheels do. It's possible to have a great-handling car with slow transitions communicated to the passenger compartment (indeed this is the holy grail of suspension design), and a terrible-handling car with fast transitions. As such, understand that the above makes no value statement about the pros/cons of air vs. coil.

    As far as the value judgements, there's been some great threads:
    Deciding on suspension, how does everyone else about air vs. coil?
    Is the air ride suspension a feature? | Forums | Tesla Motors
    S85 vs P85? - Page 4

    And so on. In summary, if you're on the fence you really need to drive them, back-to-back if possible, and decide for yourself. If you have any questions you feel are outside the scope of this thread, just PM me, I'd be happy to help. While by no means an expert, I do a lot of suspension tuning on my track car and would be happy to help where I can.
     
  15. jamieb

    jamieb Member

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    jcaspar and I work together and have almost identically-configured P85's except for suspension - I have the air, jcaspar has the coil, both 19" wheels, similar mileage. We were talking the other day about going out together and doing sound testing inside our respective cabins over the same stretches of roads to get some objective data on whether or not there is a measurable difference in road noise between the two suspensions. Does anyone know if this has been done? Does anyone have suggestions on what sort of sound testing equipment and spectrum analysis software we might want to use? Not interested in spending hundreds of $ to do this, but if anyone out there is knowledgeable about how to do this and could help us design the data collection and analysis, please let me know. Probably can't get around to doing this until late April or May but it would be fun...
     
  16. Merrill

    Merrill Active Member

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    I agree, do not feel that the air suspension is floaty at all. I'm constantly amazed that a car the weighs as much as the Model S handles to tight and has such minimal side to side yaw. I also feel that the handling has improved from the 19's to the 21's.
     
  17. Gizmotoy

    Gizmotoy Active Member

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    The ideal tool would be a spectrum analyzer (real-time if possible) that supports the audible range and provides measurements in dB. Unfortunately, professional test gear like that is very expensive, even to rent. Unless you know someone who will let you borrow theirs, you're probably out of luck at not wanting to spend hundreds of dollars.

    That said, I was surprised to find some audible-range-only spectrum analyzers on Apple's App Store, and several of them were getting excellent reviews from audio engineers looking to have a quick-and-dirty tool in their pocket at all times. I think they were something like $20. Probably worth checking out.

    Would be an interesting experiment. Gut feeling is the air is quieter, but probably not to the point where it's statistically significant.
     
  18. Carguy949

    Carguy949 Member

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    I just drove the two back to back

    I had the opportunity yesterday to drive two S60’s on 19” wheels, one with air suspension and one on coils.

    The one with air had Michelin Primacies and the one on coils had Goodyear Eagle RS-As, so it wasn’t 100% apples to apples. But reports on tirerack.com say positive things about the ride of those OEM Eagles so it may not have been much of a disadvantage.

    I drove the standard one first and I did notice that some bumps and rough pavement patches felt a bit harder than I remembered from past test drives. It wasn’t harsh, but there was a definite stiffness at times. It does make the car feel subjectively sportier, so I can see the appeal. But to me, the silkier ride of the air suspension makes the car feel more special. As we got to the end of the test drive, the product specialist was kind enough to grant my request to drive the other one for a back to back comparison.

    So we set out in the one with air. First off, I have to say the difference is not overly dramatic. But if you’re tuned in to such things, it is noticeable. The car was just a bit smoother and more polished over the same uneven pavement.

    While the car on coils feels a bit stiffer, and therefore creates a sportier impression, I didn’t find any actual difference in handling. It was a pretty short test drive, but I got to toss both cars around a few corners. Both felt flat, stable and reasonably agile. So the nicer ride doesn’t seem to extract any penalty in handling — but I guess that’s the potential advantage of air suspension.

    Some have mentioned a floaty feeling with air, but I didn’t sense that. Both cars have a a slight “squirmy” feeling at the back when you toss them around, but it’s not objectionable and seemed the same in both.

    Also, I found them equal in terms of road noise. Some have said the ones with air are quieter over bumps, but I didn’t detect that. On the 19” wheels, road noise is low in either car.

    For those on the fence here, I’m probably not helping. All I can say for sure is, Yes there is a difference, but No it’s not huge. Is it worth the cost and complexity? The best advice I’ve heard on the subject is that you have to drive both and decide for yourself. The whole mess of pros and cons and tradeoffs between refinement, sporty feel, cost, smoothness, complexity is one you have to sort out for yourself. Enjoy!

    One question: I thought someone here on the forum said that air suspension is excluded from the ESA? Can you point to where it says that? My owner advisor said it is covered, plus I looked over the exclusions part of the agreement and didn’t see it excluded. Am I missing something?

    I’ve decided to go for air. To me, the car and the ride feel more premium with it, and without a handling tradeoff. And since it’s covered by the ESA I’m willing to go for it.
     
  19. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Having had both tires on my car, I disagree. The Goodyears like to skip over the pavement if the turn is at all sharp--this even happens at low speed. The Michelins stay planted. I don't think the ride is much different between the two tires though.
     
  20. neroden

    neroden Happy Model S Owner

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    Ah. I can tell you something about this, having driven a loaner with coil suspension as well as my air suspension.

    The coil suspension reacts a lot worse to potholes and seriously damaged/bumpy roads, such as we have so many of in NY. The coils "bounce" with "aftershocks" after every bump.l The air suspension muffles the shock from road bumps a lot better. You only feel each bump once, and they're all sort of "muted". (You can still feel all of them, but they're less shocking.)

    Most of the other things about the "ride quality" -- ride quality on *good roads* -- are the same between air and coil; but on *bad roads* the air suspension will be more comfortable. Now you know!

    The quiet is due more to the 19" -- the 21" are loud.

    You want air suspension and 19" tires.

    - - - Updated - - -

    Well, I was looking for a land boat / Lincoln Town Car substitute more than a sports car substitute, but I totally understand what you're saying.

    The air suspension is a bit floaty. I can still feel every single bump, though. They're just less shocking and I no longer wince and tense up. I was very happy with that. If I were on better-maintained roads, I probably wouldn't care, but the roads around here are completely beat up, and when 4" deep potholes are fairly normal, you want the bumps to be muted. It sounds like the original poster on Long Island is dealing with similarly bad roads.
     

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