NigelM
Recovering Member
I can't imagine there would be any noticeable range difference between the 19" and 21" wheels.
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I can't imagine there would be any noticeable range difference between the 19" and 21" wheels.
JakeP
S P4996 ==> P02547
I had a Tesla rep tell me today that the 21" wheels, mostly due to the performance tires, could yield up to a 5% range loss. This was the first quantification of this I had heard from Tesla, despite having asked before.
stopcrazypp
Well-Known Member
On the return trip the guy who drove turned the air con off and kept the windows open at 55mph. Wouldn't it be more efficient to use the fans or turn the air con to a higher temp (not the 72F they like to turn it to, but something closer to 77F/25C)?
CapitalistOppressor
Active Member
Goodness knows I'd like to see real world data on that. Speculation has been that rolling down the windows is worse than just turning the A/C on to to something reasonable.
Makes sense. I had a Tesla engineer tell me that aerodynamically, the 19/21" wheels were basically the same. I know from experience that tires even in the same size and similar type can result in a substantial hit to efficiency.
ljbad4life
Member
I have heard anywhere from a 5-10% efficiency difference between 19-21" tires. That it has more to do with low profile tires than the actual size of the rim, but the rim size still matters. I just want real world confirmation of whether there is a difference.
It's there but you'd need really accurate instruments (laboratory grade) to measure the reduction in range the 21" wheels would account for. And this would almost all show up in city driving where range isn't as important. What the 21" wheels have, compared to the 19" wheels, is more mass further away from the centre of rotation so the amount of power to get them up to speed is slightly more. (Inertia equals mass times radius squared if I recall correctly).
However, compared to the differences that tires can have, the wheel difference is hardly worth mentioning. Okay, some back of the napkin numbers:
For ease of calculation, mass of the 19" rim component of the wheel = 1.
19" wheel 9.5[SUP]2[/SUP] = 90
21" wheel 1.1 * 10.5[SUP]2[/SUP] = 110 (We'll WAG the rim component of the 21" wheel to be 10% heavier because there is both more circumference and more width. Anyone who wishes can cut off the spokes of one of their 19" and 21" wheels to get an accurate weight difference.)
Tire 13.5[SUP]2[/SUP] = 180 (both tires have the same radius)
So the tire has between 160% for the 21" wheel to 200% for the 19" wheel of the inertia of the wheel. This assumes the tread portion of both tires weigh the same, which is unlikely. And it doesn't take into account the stickier tread compound typically found on lower profile tires. The stickiness of the tread compound plus the additional flexing of the wider tread width on the 21" tire impact highway driving more than the inertia of the wheels do.
Okay Jerry, you have really passed my pay grade on this one! Needless to say you really know your stuff. Let me ask you another question. I ordered the performance but choose the 19" tires based on other conversations we had. Do you think I will suffer a significant decrease in 0-60 times on the rare occasion I floor it?
I assumed I would lose some because of less grip but I hope it's not all lost. Thanks as always. Your knowledge on this stuff is impressive.
On track day? You betcha.
In normal street use? That's kind of a how long is a piece of string question because there are so many factors including what you think is significant. There's really only one way to answer that question and that is to do a test drive. Barring that, I'd say that if those rare times when you floor it are to blow away the XXX in the next lane then maybe. If you're just trying to impress the people sitting in the car with you, there will be plenty of Telsa grins unless maybe your passenger is someone like Gilles Villeneuve.
Another way to look at it is: The non-performance 85 kWh is 5.6 seconds. The Performance with 21" is 4.4. There's no way the different tires are going to bring the Performance down to the non-performance times because there is a big difference in motor-power between the two. Splitting the difference is 5.0 but my guess would be it will do better than that given a good road surface.
And when the OE tires wear out, you can always buy some sticky 19" tires. I'm guessing that it won't be all that long before Yokohama or Toyo comes out with some A048s or Proxes in the 19" size for the Model S even though they don't show that size on their websites. In fact, you might give their technical departments a ring.
Continental has the OEM 21" tire (Continental ExtremeContact DW) in the 19" size. Toss those on and I'd bet you couldn't tell the difference between the two tire/wheel setups in a blind test. If anyone you might find that the 19" setup accelerates slightly better since they will have less rotational inertia.
I will send you an email before I buy my first replacement tires. Thanks as always.
Perhaps MT could have used these to improve the range on the Model S? How Lobster-Inspired Winglets Reduce Drag, Increase Fuel Efficiency | Autopia | Wired.com
<rant>
21st century infomercial product. With all of the time that Nissan, GM, Tesla, Toyota, Honda, professional auto racing teams, and others have put into wind tunnel testing, how is it that a product like this isn't standard on every vehicle out there? Heck, betcha Elon would have allowed the XM-Radio Shark Fin antenna if it had reduced drag, as it's similarly shaped to these magic, placebo-like bumps.
I don't doubt they have data to back up their claims. When I switched out the tires on my 2008 Prius with Goodyear's fuel-efficient tires a couple of years ago, my mileage went up by about 10%. Of course, I was also paying A LOT more attention to my mileage and to driving more efficiently. I think I read somewhere in these forums that the most effective thing that has improved fuel efficiency in cars in recent years has been charting fuel efficiency in cars and the natural human tendency to want to compete with yourself and others.
But that's just my opinion. I could be wrong.
</rant>
I certainly compete with myself, and so far I've won
2004 Prius MPG from the logbook. (Complete years only):
2003-2004 -- 50.8 mpg 17,628 miles
2005 -- 52.6 mpg 14,688 miles
2006 -- 56.3 mpg 16,174 miles
2007 -- 57.3 mpg 18,384 miles
2008 -- 59.9 mpg 21,755 miles
2009 -- 61.4 mpg 16,177 miles
2010 -- 65.2 mpg 12,134 miles
2011 -- 66.9 mpg 11,272 miles
I certainly compete with myself, and so far I've won
2004 Prius MPG from the logbook. (Complete years only):
2003-2004 -- 50.8 mpg 17,628 miles
2005 -- 52.6 mpg 14,688 miles
2006 -- 56.3 mpg 16,174 miles
2007 -- 57.3 mpg 18,384 miles
2008 -- 59.9 mpg 21,755 miles
2009 -- 61.4 mpg 16,177 miles
2010 -- 65.2 mpg 12,134 miles
2011 -- 66.9 mpg 11,272 miles
Wow. Those are great scores. I'll consider my ass officially kicked. I'm usually in the low-mid 40's.
gg_got_a_tesla
Model S: VIN 65513, Model 3: VIN 1913
I certainly compete with myself, and so far I've won
2004 Prius MPG from the logbook. (Complete years only):
2003-2004 -- 50.8 mpg 17,628 miles
2005 -- 52.6 mpg 14,688 miles
2006 -- 56.3 mpg 16,174 miles
2007 -- 57.3 mpg 18,384 miles
2008 -- 59.9 mpg 21,755 miles
2009 -- 61.4 mpg 16,177 miles
2010 -- 65.2 mpg 12,134 miles
2011 -- 66.9 mpg 11,272 miles
I don't want to be stuck behind you in the left-most lane on a freeway, Jerry :tongue:
Seriously, well done!
Not to worry. I'm not a "left lane driver" except before a left hand turn. Though on my trips to Nebraska I do get up to 80 mph and I still get 55 to 60 mpg during them. It's just knowing when to do so that's the trick. I can't wait to figure out how the Model S works.
Thanks.
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