Newbie Question: Air Suspension vs Standard

[dave]

Here's what I've gathered from the forum:

1. Be sure the tires are inflated properly.

2. Be sure the lug nuts are torqued properly (129 ft. lbs.)

3. Have Tesla check the torque on the suspension bolts.

If all of that fails, get the plus upgrade.

Thanks Jerry. Yeah I'm on top of the tire pressure and lug nuts. I swap out my own wheels for winter. I may get Tesla to check the suspension bolts, but I'm thinking it is the design of the suspension itself, not just a loose bolt kinda thing.

As for the plus upgrade, that will only be my dreams. I rationalized this car out for the next 8 years, and I can't put another penny into her!

 

[jcaspar]

I have coils and a steep driveway. I'm glad I got the coils as an air car's scrape in the drive but my coil doesn't. If I had air I would need to raise the car every time just to get in and out of my driveway.

 

[brianman]

Do you have any more info on this? I have an early P85 (late 2012) with air suspension and I hate the swaying, swishy feeling of the suspension. I haven't driven anything else to compare with. Is there anything I can do to get rid of that feeling? I have historically been a "sport" suspension guy, rather than "comfort" mode.

Check your lugnuts before considering anything more expensive.

Edit: Looks like you already covered that. Mea culpa.

 

[Carguy949]

Thank you for all your replies

I have coils and a steep driveway. I'm glad I got the coils as an air car's scrape in the drive but my coil doesn't. If I had air I would need to raise the car every time just to get in and out of my driveway.

Thank you, everyone, for the info. Based on what I'm hearing and since I don't have a steep driveway to contend with, I'll go with the standard suspension. I plan to keep the car over 5 years, so the simplicity of that is appealing.

 

[bellwilliam]

"Range decreases slightly with larger wheels. 21" wheels have more contact with the road "

middle high physics will tell you that is not possible. same car, no matter what size tires you run will have same contact patch everything else being equal.
it is the shape of the contact patch that determines mpg, handling, etc....not the size of contact patches.

 

[Jason S]

middle high physics will tell you that is not possible. same car, no matter what size tires you run will have same contact patch everything else being equal.
it is the shape of the contact patch that determines mpg, handling, etc....not the size of contact patches.

Ok, I went the chemistry path for all the sciences but I still can't figure how the width of the tire doesn't impact its contact patch. The 21" tires are wider edge to edge as well as taller, are they not?

 

[brianstorms]

I got 19" wheels and standard suspension, and thought that was fine, but if I were to buy another Model S, I would get air suspension, if for no other reason than I have finally found a place in town that I occasionally visit whose parking garage entrance has a hump you have to drive over that's just enough to cause a GROOOOANNNN SCREECH as you drive over it. It's a movie theatre's parking garage. I haven't figured out a way to get in yet that doesn't cause the contact with the underside of the car... and even if I go over the hump at like 1mph, I still get contact which sounds horrible.

It'd be nice to press a button or something and have the car lift itself up for a bit in those situations

 

[lolachampcar]

I believe there are tell tales on the bottom of the car that allow Tesla to keep track of your bottoming out. Too much and I suspect there are warranty implications (although I was having no luck having that conversation).

WRT contact patch size, the idea is that, for a given air pressure, the amount of tire that must be pushed against the road to support the corner of the car is the same. It literally is a Pounds Per Square Inch times Square Inches to get the Pounds you need. If your tire is wider, there is less depth to maintain the same area.

Given the amount of effort that other disciplines put into managing air around tires, I believe it is the width of the rotating section that affects drag.

 

[jerry33]

Ok, I went the chemistry path for all the sciences but I still can't figure how the width of the tire doesn't impact its contact patch. The 21" tires are wider edge to edge as well as taller, are they not?

1. Contact patch area is determined by tire pressure. Take the load on the tire divide that by the air pressure, and you have the contact patch. (There will be slight variances depending on the stiffness of the tire, but not enough to matter for practical purposes).

2. For a given car, increasing the diameter of the of the wheel means that the aspect ratio is reduced. The overall diameter will be the same, so the tire isn't actually taller.

3. As the aspect ratio gets lower, the tread becomes slightly wider for any given nominal section width because the sidewall will have less curvature.

 

[lloyds]

Onto our 2nd + and we didn't even think twice about the air suspension. It is so convenient and love the adjustability with a tap on the screen. No more bottoming out and scraped up front bumper.

 

[studiojon]

I honestly think that the air suspension is more comfortable in addition to being more useful. The coils are a bit more "jittery" on uneven roads. I would get air every time.

 

[yobigd20]

middle high physics will tell you that is not possible. same car, no matter what size tires you run will have same contact patch everything else being equal.
it is the shape of the contact patch that determines mpg, handling, etc....not the size of contact patches.

dude, that's the quote straight off the web site, not mine. I'm right there with ya. Had 100 average in physics. chemistry too. probably would have gone down one of those routes if was wasn't so damn good at software engineering. Apparently whoever wrote that on Tesla's web site never got through middle school. That could explain a few other fallacies on there too lol

 

[jerry33]

dude, that's the quote straight off the web site, not mine. I'm right there with ya. Had 100 average in physics. chemistry too. probably would have gone down one of those routes if was wasn't so damn good at software engineering. Apparently whoever wrote that on Tesla's web site never got through middle school. That could explain a few other fallacies on there too lol

Well, if the tread is softer it will wrap around very small road irregularities which increases the contact with the road. Note that they said "increases the contact with the road" not "increases contact area". This is one of those "Ya really gotsta read the fine print carefully" statements.

 

[yobigd20]

Well, if the tread is softer it will wrap around very small road irregularities which increases the contact with the road. Note that they said "increases the contact with the road" not "increases contact area". This is one of those "Ya really gotsta read the fine print carefully" statements.

hey I never said I was any good are reading or English either.

 

[muleferg]

Standard for me.

 

[N4HHE]

I was informed by one of the SC personnel that the 21" wheels actually provide slightly more range than the 19" wheels. This was due to the outside diameter of the tire being larger than the 19s making the motor not have to spin as fast at highway speeds. I'm still trying to do the math in my head on how that works, but that's what he said.

Thats disappointing misinformation to be coming from an SC. It might apply to an internal combustion engine which usually consumes more fuel when asked to do the same work at higher RPM than lower. It does not apply to electric motors, especially when considering two nearly identical operating RPMs.

Its not even a hard and fast rule for internal combustion engines. About 14 years ago I was riding a Honda PC800 among a pack of about 20 other PC800's on the Blue Ridge Parkway. We were being good citizens riding 40 to almost 50 MPH in 45 zone. The PC800 will pull those speeds in 5th gear. Think we rode from Cherokee to Ashville. Bought fuel and compared results. There were two distinct results, something like 42 MPG and 50 MPG. What was mostly unexpected was the 50 MPG group rode in 4th gear at about 4000 RPM while the 42 MPG group rode in 5th at about 3500 RPM.

Another example was of a friend with a 1992 Toyota 4x4 pickup who often towed his 4500 bass boat. He found when pulling the boat the engine screamed in 4th gear at 70 MPH but it got better MPG than in 5th.

More recently I had a 2008 F-250 Powerstroke diesel with 3.55:1 gears. A friend had same thing but 3.73:1 gears. I got better MPG empty than he. He got better MPG than I pulling the same RV.

 

[jerry33]

Thats disappointing misinformation to be coming from an SC. It might apply to an internal combustion engine which usually consumes more fuel when asked to do the same work at higher RPM than lower. It does not apply to electric motors, especially when considering two nearly identical operating RPMs.

It won't apply to ICE cars either because the 19" and 21" tires have virtually the same RPMs and outside diameter due to their different aspect ratios. The difference in range is going to be mostly because of tire construction/compounds. (Although the 21" would always have lower range if the tires were equal except for the size. However, this almost never happens.) The main reason for the bad information is that most automotive service people don't seem to have much of a clue about tires. This isn't surprising because most automotive technical training focuses on the engine and transmission.