2013 Tesla Model S P85+ Long-Term Update 3
Oh, and it got a new motor. A New Motor!
I'm not a big fan of sunroofs but if you remember the arrival story for our long-term Tesla Model S, Elon Musk personally made sure that our car had the glass top anyway -- and understandably so, because it really is pretty cool. Unfortunately, it's also been creaking at times (to my ears, often sounding like Dizzy Gillespie's Salt Peanuts being tapped in Morse Code).
And in an otherwise extremely quiet car, this really stands out. So much so that I usually find myself turning-up the music to drown it out (though I'd probably have turned it up anyway). The local Tesla Service Center had made a valiant effort to squelch the gremlin, but it came back, and so I scheduled another visit and the car was picked-up by their concierge service.
Later in the day I received an email. "Is there anything odd about the car's steering?" they asked. I typed back "Maybe a slight clunk at full lock, but it's no biggie" (I've felt the same thing in many other cars). However, this was followed by a more ominous question: "Does the car shimmy when you stop?" "No, not that I can tell," I added, "but gosh, you're the service folks, so do whatever you think needs to be done."
A few days later I got another email "Your car will be returned today. We replaced a slightly out of spec right steering knuckle. And the drivetrain."
I read it again. Replaced the Drivetrain! "There was nothing wrong with the power unit" they noted, "but we heard a clicking in the transmission. The power unit isn't serviceable in the shop so we decided to be proactive." As if they were replacing a windshield wiper. Wow. The new motor might have a bit more low-speed hum but otherwise, the car drives exactly the same.
And let me guess -- you're tapping your fingers right now thinking Motor Trend's long-term Model S is simply being given the red carpet treatment. Well, I guess it's possible. But frankly, the sense I got from the service guys was that the whole episode amounted to just another day at the office. Which makes for an extraordinary level of service in my opinion.
However the powertrain swap does lead us to the broader question of how well our car's been holding up. Answer: so far, so good. What with it being constructed of aluminum and other lightweight bits, I've been watching things rather closely, and it's actually been staying stuck together pretty well. (Helped, I'd note, by additional 'proactive' work back when its second-row cupholders were installed -- the bumper carrier bolts were replaced, while foam tape and Loctite was added to the body-sides bright-work, apparently to better secure it -- all at no charge).
However, an area that has drawn our attention is the wear rate of the rear tires. After noticing a bubble in the right front sidewall (the curse of 21-inch wheels) the tire was replaced, and while we were at it, so were the other three a short time later (to maintain equal tread-depth all around). But before the new rubber went on, I measured their tread depths, and then the depths of the new (and identical) Michelin Pilot Sport 2's. At 9560 miles, the left front had lost at least 10 percent of its depth while the rears had lost an average of 38 percent of theirs. Is that particularly bad?
I contacted expert Woody Rogers at the Tire Rack, who actually thought the numbers weren't out of line for these tires fitted on a car of this weight in this performance category - though he cautioned that tires wear more quickly at first with the rate only becoming linear (and more predictable) once they're at around 12,000 to 14,000 miles.
"For cars like Porsche, BMW, Mercedes, or the Cadillac CTS-V" Woody noted, "history has shown us that most RWD performance cars wear their rear tires at about twice the rate as their fronts. Realize that for performance cars it takes only a few ounces of pedal pressure to unleash hundreds of pounds of torque. And by that, I don't mean the driver is doing smoky burnouts from every stop light - just squeezing the throttle to move the car in traffic."
And even though our car wears the staggered tire sizes that are part of the Performance Plus package (245-mm front, 265-mm rear) its ratio of tire widths (48 percent front, 52 percent rear) still isn't extreme enough to match the car's even greater rear weight bias (46 percent front, 54 percent rear). In other words, its rear tire-width bias is 4 percent while its rear weight bias is 8 percent. Twice as much.
Making matters worse (for rear tire wear) is an electric motor's otherwise wonderful attribute of delivering its torque (the Tesla has 443 lb-ft of it) very suddenly, all the way down to zero rpm. "This," Woody added, "circles back to that few ounces of pedal pressure concept which might result in a little faster wear rate on the Tesla versus a conventional performance sedan. I recall talking with a Michelin race tire engineer who told me they had to redesign their racing slicks for LeMans when they started working with the Audi diesel program because of the diesel's greater torque and the wear rate it created." It's ironic to me that a car that's capable of the Model S's astounding efficiency -- we've been getting 86.5 mpge -- might also be inclined to wear its tires more rapidly.
But there's actually even more going on here, as the rear tires of the Model S are additionally burdened with Tesla's unusually high level of regen (the motor acting as a generator) when you lift off the accelerator pedal. It's there for a good reason, of course – improving efficiency and range (and once you get the hang of it, it's kind of cool to virtually drive with one pedal in light traffic).
So, being a guy who likes to see things as graphs, I did a brief test with our Model S and a handy Cadillac CTS Vsport, repeatedly pressing and lifting their accelerator pedals at 40 mph, while marking those instances with a hand-held button.
And the differences are visually dramatic as the sensations feel. The Tesla reacts almost instantly to nailing the throttle (there's maybe a 0.05 sec delay) while the Cadillac takes a full second to seriously begin accelerating. Meanwhile, lifting the CTS Vsport's throttle generates about 0.06 g's of deceleration, while the Model S produces about 0.16 g's – which is enough to let you do quick speed corrections without the time delay of moving your foot to the brake. Frankly, the shapes of these curves are of absolutely paramount in understanding why the Model S is so addictive to drive in the real world. While there's a handful of sedans as fast as the Tesla (and only a couple that are faster) none come close to its lighting reactions. You can dispatch unsuspecting cars (some of them, very powerful Audis and BMWs) with a violence that borders on cruel... but at the price of possibly wearing its rear tires more quickly.
Oh, and speaking of driving – you guessed it -- when I drove the car home after the powertrain's replacement, the sunroof's creaking … resumed. It has another appointment next week.
More on our long-term 2013 Tesla Model S P85+:
|Service life||5 mo/13,452 mi|
|Average fuel economy||86.5 MPGE|
|EPA City/Hwy/Comb Fuel Econ||88/90/89 MPG|
|Energy consumption||39 kW-hr/100 mi|