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Model S options

Let's discuss what options we need in the model S.
I can start by listing some luxury car essentials:
1. Rear view camera
2. Parking sensors
3. Adaptive cruise control
4. Highway lane departure sensors
5. Headlights turning with a turn of the wheel
6. Premium sound with capability to store MP3 songs
7. DVD video for back seats
8. Tire pressure sensors

Also looking for some electric car features like:
1. GPS to show electric driving range radius
2. Temperature of the batteries
3. GPS to estimate charge needed to reach destination
4. Instant efficiency measure of some kind (similar to instant mpg)

The SPECS page lists TPMS as standard.

Instrumentation
17" capacitive touchscreen with media, communication, cabin, and vehicle controls
Bluetooth wireless technology for hands-free calling and streaming music
Three spoke, multi-function steering wheel with tactile controls
Tire pressure monitoring system

From the Edmunds Site:
TPMS: Mandated by the Federal Government
If you're driving a car, truck or SUV built in the past few years, there's a good chance that it has a TPMS. Starting with all 2008 models, in fact, it's a required feature. In response to the rollover incidents involving the Ford Explorer and Firestone tires, Congress enacted the TREAD Act in 2000. Part of this act got the process moving for having a TPMS in every vehicle.

AGENCY: National Highway Traffic Safety Administration (NHTSA), DOT.

ACTION: Notice of proposed rulemaking.

SUMMARY: This notice of proposed rulemaking (NPRM) proposes to establish a new Federal motor vehicle safety standard mandating tire pressure monitoring systems capable of detecting when a tire is significantly under-inflated. A prior version of the standard, adopted by the agency in June 2002 in response to a mandate in the Transportation Recall Enhancement, Accountability and Documentation Act, was vacated by a decision issued by the U.S. Court of Appeals for the Second Circuit in August 2003. This NPRM, which is consistent with the Court's decision, proposes to require installation in new light vehicles of a tire pressure monitoring system capable of four-tire, 25-percent under-inflation detection. This proposed rule differs from the final rule also in that it tentatively responds to issues raised in petitions for reconsideration of the June 2002 final rule and proposes to require a TPMS malfunction indicator.

reitmanr,

TPMS is required but what's wanted is the actual tire pressure to display on the screen the way many cars do, not just a warning when the pressure falls 25% (which is way too late to prevent tire degradation). Even better would be a way to adjust the pressure from the screen (although I suppose many folks would do it very wrong by letting out pressure while driving. A big no-no).

I've never seen a good "solution" to the issue of optimum pressure parked vs. rolling, etc. As the tire warms, pressure rises. 'Druthers would be 4 scales with an 'optimum' band for the current speed, miles driven to warm, etc., taken into account -- and automatically adjusted for. And a specific warning for a) underinflation b) overinflation and c) leakage.

(4 scales = 1 for each tire, of course.)

Brian,

As you drive tires eventually reach a thermal equilibrium where the amount of heat gained by flexing equals the amount of cooling. There are really just two choices:

1. Inflate the tires low and they will inflate themselves but the tire temperature will be very hot.

2. Put some air into the tires so that they stay cool.

Note that in both cases the pressure reached will be similar but the temperature of the tires will not be. It's heat that kills tires, not pressure.

Typically you get an 8% to 10% increase in pressure after an hour or two's drive. That might be as high as 15% if the day gets significantly warmer (as it does in desert areas). Any pressure rise higher than that indicates a problem (which is often too low of a pressure to start with).

Bear in mind that every tire load/inflation chart is based on 65F ambient temperature. If the weather is warmer you need to increase the pressure to compensate. Also if the weather is cooler and you inflate inside you need to increase the pressure because the warmer garage air will shrink in cold weather. (yes, there are charts for this)

Jerry3 - if you had only a mediocre pressure gauge (like the one on gas station air hoses) that was hard to read with much exactitude, would you recommend OVER pressure (by 5-10#) to be safe? Perhaps also to drive home, let tires cool down and then release any excess pressure the next morning?

I would not recommend over inflation, in general. For a firmer ride, or with a near max load, you might exceed the auto label's recommended pressure by up to 5 pounds, but both under and over inflation have their handling risks and can cause uneven wear.

Teoatawki,

Adjusting tire pressures for conditions is not overinflation. The tire pressures on the vehicle placard are based on a set of assumptions. Change those assumptions and you need to adjust the pressure for best results.

pilotSteve,

You can't trust any gauge at a gas station, tire store, or car dealer to be within 10 psi of the correct pressure. Get a good pressure guage such as 50406
http://www.racerpartswholesale.com/product/LAR_50406_Longacre_Quick_Fill...
or model 50404
http://www.longacreracing.com/catalog/item.asp?id=217&catid=8

With TPMS you should be able to adjust the setting so that you are alerted when the pressure drops more than a couple of PSI from the setting you wish to run it at. When it alerts you can then visually inspect the tire (assuming you don't have access to your own gauge and add pressure until the alert stops. Unfortunately, the default for TMPS is 25% low. By the time the tire loses that much pressure, it's already degraded.

@jerry3

Thanks for the recommendations re: tire pressure & gauges. I'm thinking of ordering The 404 above and keeping it in the glove box.

@jerry3 - thanks for your recommendation and always insightful tire information. I've learned more about tires, wheels, suspensions, etc. by reading your posts that any other source!

I also bought the 404 as its time for me to have a precision gauge not my dimestore cheapie!

Indeed‼ S/b standard owners' equipment. HOWSOMEEVER -- Keep in mind the temperature and pressure changes caused by driving/parking! A "proper" setting while cold may turn into serious overinflation after an hour at 70 mph. Or sooner.

Brian,

100% wrong. Tires are designed for that. The only pressure that is important is cold-first-thing-in-the-morning-before-driving pressure. That's why, on the sidewalls of the tires, the maximum pressure is stated as being maximum pressure cold.

Driving will cause the tires to flex which heats up the tires and increases the pressure which reduces the flexing which reduces additional heat build up and so on. Eventually the tires reach a point called "thermal equilibrium" where the heat gained from flexing is the same as the heat lost from cooling.

You have two choices:

1. Put enough air in the tires to reduce the heat build up.

2. Put less air in the tires and have the tire built up the pressure on its own.

In either case the tires will eventually get to the same pressure, but if you have chosen #2, the tire temperature will be far higher.

Heat, not pressure, is what kills tires.

You can tell that you are doing it correctly if after an hour or two of highway driving the tires have increased no more than 8% to 10% (If the day gets much hotter, as it does in desert conditions, there might be as much as a 15% increase. More than that and you need to figure out what's wrong--often it's too low of a pressure to start with.)

The absolutely worst thing you can do to your tires is to let pressure out of a tire that has been driving for a while and has built up heat. That will just start the flexing cycle all over again and cause the tire to get even hotter--perhaps so hot that the tire will start to devulcanize or even catch on fire.

Yes, I guess I was thinking of the case where a driver comes off the freeway and checks the pressure, and compares that to the "cold" recommended. Or reinflates a low tire (just off the freeway) to only the "cold" pressure.

I have a tyre pressure gauge & compressor in my garage - that way it's easy to check the cold pressures before driving off.. Not expensive to do and worth it.

You can choose from one of ten different voices, that you can pick from the screen. And they all have their own way of hooking in with the GPS as well:

1) Incredibly sexy voice (interactive)...what Siri should have been. Maybe Michelle Pfeiffer just waking up..
2) Arnold Schwartzenpuffer.
3) Sean Connery
4) Morgan Freeman
5) James Earl Jones (not sure if he's available...has he "moved on"?)
6) Jack Nicholson
7) Ian McKellan
8) R. Lee Ermey
9) Anthony Hopkin
10) John Malkovich


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