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Air Suspension
- Thread starter Todd Burch
- Start date
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- Driving Dynamics Model S
strider
Active Member
Springs last a long time but shock absorbers do not. The standard suspension will use conventional shocks/struts that will need to be replaced periodically.
I just had to replace a broken front spring on my 8 year old VW TDI with 84kmiles on the clock...
Raffy.Roma
Rome (Italy)
So as I thought it's not a rule that standard suspension are more reliable than air suspension.
Right but the replacement costs can be high on the air suspension. On our MB GL450 is was around $4k when the front air suspension went out after 60k miles.
Raffy.Roma
Rome (Italy)
In my opinion safety and comfort come first than maintenance or replacement cost. And then air suspension can also help to save energy. That's why I would prefer air suspension.
Can someone please back up with some data how air suspension can help to save energy? Certainly energy is used to raise and lower the car automatically on the highway. It is also used when manually raising the car. This car weighs over 2 tons so this isn't a free lunch. Air suspension saves some energy by slightly reducing drag at highway speeds. But is this really enough on balance to offset the energy used in raising and lowering the car all the time? Or is the energy savings dependent on how much time a driver spends on the road at highway speeds?
No data, but if you think of the suspension as controlling the wheels' movement, then keeping the car's height above the road constant despite wheel jouncing should be more efficient than regaining height after bouncing.
Obviously, if you raise/lower the suspension every block it's going to use more energy. However, used normally:
1. Air suspension lowers the car height at highway speeds reducing aerodynamic drag.
2. Air suspension should keep the bouncing of the wheels over uneven pavement to a minimum. Moving unsprung weight (basically tires, wheels, and brakes) up and down increases energy use. (Brian has already mentioned the reduced body movement.) I'd suggest this is particularly important in the Model S because of the low profile tires that don't have all that much cushioning ability to start with (regardless of 19" or 21").
So there is energy use reduction at both highway speeds and city speeds.
At 60 mph an outside mirror uses about 1 hp of energy. Lowering the vehicle by 25 mm reduces the frontal area by more than the area of an outside mirror. In addition, the less air you have going under the car the less drag there is because there is turbulence caused by the non-moving ground and the moving vehicle. So the reduced drag is actually significant.
I don't believe there will be actual numbers until there are both air suspension and spring suspension cars to compare.
Raffy.Roma
Rome (Italy)
I agree with you Jerry. Not only air suspension are useful to get energy saving but they can also lower automatically when people get on and off the car, they can match to the features of the weather and of the road where you are driving to get more comfort and safety in all conditions.
There is some yet to be confirmed information about the Model S air suspension you might find useful on the beginning of an FAQ doc in progress:
Welcome to Google Docs
One aspect no one has mentioned is that the air suspension maintains the Model S's height under load. Also, being able to raise the car manually allows you to travel in deeper snow and rutted roads at slow speeds with less chance of getting stuck or scraping/bumping the battery pack.
Welcome to Google Docs
One aspect no one has mentioned is that the air suspension maintains the Model S's height under load. Also, being able to raise the car manually allows you to travel in deeper snow and rutted roads at slow speeds with less chance of getting stuck or scraping/bumping the battery pack.
Raffy.Roma
Rome (Italy)
Raffy.Roma
Rome (Italy)
goyogi
Member
Another pro is that with such a quiet car even though it's hopefully well built, squeaks and rattles can happen over time. An air suspension can help prevent that by preventing jarring conditions to the body.
ToddRLockwood
Active Member
Air suspension has the benefit of being actively adaptive and driver-adjustable. The way the Model S lowers itself as the speed increases is thanks to air suspension. There are other active systems, such as GM's Magneride, that change the stiffness of the shocks on the fly, but they can't change the ride height. Tesla made a good choice for the Model S. If they get around to developing a supercar, active shocks may play a role as well.
Active shock systems first appeared on the Ferrari Mondial t (the car in the movie, Scent of a Woman) and further refined on the F355. The system used accelerometers to control the four shocks in realtime. For example, in a hard left turn, the system would stiffen the shocks on the right side of the car, while softening those on the left side. It was developed by Bilstein and Ferrari. They actually had stepper motors attached to the adjustment screw on the upper end of each shock. GM vastly improved on the concept with Magneride. The GM shocks use a special oil containing iron particles in suspension. The shock's firmness is increased by applying a current to an electromagnet inside the shock. The viscosity of the oil is temporarily increased by the magnetic charge. Pretty cool solution, and no more moving parts than a standard shock. Magneride is so fast, it can actually adjust for individual bumps in the road. It's been available on Cadillac and Corvette for several years. -Todd
Active shock systems first appeared on the Ferrari Mondial t (the car in the movie, Scent of a Woman) and further refined on the F355. The system used accelerometers to control the four shocks in realtime. For example, in a hard left turn, the system would stiffen the shocks on the right side of the car, while softening those on the left side. It was developed by Bilstein and Ferrari. They actually had stepper motors attached to the adjustment screw on the upper end of each shock. GM vastly improved on the concept with Magneride. The GM shocks use a special oil containing iron particles in suspension. The shock's firmness is increased by applying a current to an electromagnet inside the shock. The viscosity of the oil is temporarily increased by the magnetic charge. Pretty cool solution, and no more moving parts than a standard shock. Magneride is so fast, it can actually adjust for individual bumps in the road. It's been available on Cadillac and Corvette for several years. -Todd
mnx
2018 M3P
Also used in the Ferrari 458, and Range Rover Evoque.
From MT's best drivers car 2012...
"The Camaro also has GM’s revolutionary magnetorheological fluid shocks, which are just about the best game in town when it comes to balancing ride with handling. It struck me that last year’s BDC winner, the Ferrari 458 Italia, comes with similar magnetic dampers licensed from GM. As does our 2012 SUV of the Year, the Range Rover Evoque. Point is, these high-tech magnetic dampers are really and truly great -- and they work magic in this big-boy Camaro."
Read more: 2012 Motor Trend Best Driver's Car - Motor Trend
From MT's best drivers car 2012...
"The Camaro also has GM’s revolutionary magnetorheological fluid shocks, which are just about the best game in town when it comes to balancing ride with handling. It struck me that last year’s BDC winner, the Ferrari 458 Italia, comes with similar magnetic dampers licensed from GM. As does our 2012 SUV of the Year, the Range Rover Evoque. Point is, these high-tech magnetic dampers are really and truly great -- and they work magic in this big-boy Camaro."
Read more: 2012 Motor Trend Best Driver's Car - Motor Trend
And then there's the supposedly revolutionary Bose suspension. Looks great in the lab, so one wonders why it hasn't been picked up by anyone.
