Tesla Efficiency part1: Tires/Wheels

The $15K Tesla post, still the most popular recent post on the site, really didn't go into the efficiency or cost to operate or any of that. Obviously it's early days so a lot of that wasn't known yet and anything said would mostly be expectations and/or speculation.   Since it, like previous cars, will probably be doing 15K-20K miles/year, efficiency, along with reliability, are going to be a really important topics. Impatient people can skip all the details to "Yes, it worked!" below.

There is one part(s) on the car that has the biggest impact on noise and comfort and efficiency.
That of course is tires.  The car we got has/had the $1500 optional Sport 19" Wheels. These are targeted at the performance oriented driver without being quite as punishing as the 20" wheels on the Performance Model 3.

18", 19" 20" ... it doesn't sound like all that big a difference, but the tire sidewall, the part that flexes over bumps and road imperfections, is actually twice as tall on the 18 vs. the 20. It ends up being a bigger deal than you'd expect.
Any of the vehicles we saw which had the more efficient 18" wheels were either more expensive or had the wrong battery or no heat-pump or had way more miles.  Things that were much more difficult to change.

The 'Before' picture. 19" Sport Wheels, Junk tires from Hertz

The biggest thing we were looking for with the 'base' 18" Aero Wheels was that the taller sidewall can be (and is) softer, more flexible. As a result the car does not lose as much energy/friction making a short stiff sidewall flex with each revolution of the wheel. As you'll see in a moment this has a larger effect than you might anticipate. The taller more flexible sidewall also results in a slightly more comfortable ride and it transmits less road surface noise into the body of the car. 

There is of course a tradeoff.

Traction, right at the limit of adhesion as the tire is starting to break free and skid is slightly compromised.
Likewise ultimate braking performance on a clean flat dry road may see a couple percent difference.
Note though these are differences smaller than produced by a little dampness or a different road surface or temperature or ...  In other words things rarely perceivable in real world situations. Granted the 19" and especially 20" do really feel 'more connected' especially during hard cornering, but you do give up quite a lot for that 'feel.' As previous owners of Porsche 911, Porsche 928, Audi Coupe GT and SAAB Turbo 3DR we do know a little about driving feel.

Once we had the car with the 'wrong' wheels and tires it was time to look for the right ones.
fleaBay was checked to determine current used Tesla 18" Aero wheel pricing (about $200 ea. including shipping) and then the search widened to Craigslist and FB Marketplace. We're not FB fans, but that marketplace has a lot more of this kind of stuff, as well as being a hotbed for scammers. A couple days on both of those turned up a set of four with completely trashed tires without TPMS (the pressure sensors) for $500. 

We have a car that uses the latest bluetooth based TPMS system. Early (mid 2021 and before) wheelsets would have the wrong sensors in them, so 'without' wasn't a bad choice. OTOH if you buy the sensors from Tesla it's almost $100 each. Fortunately we have good sensors right in the wheels on the car, so it's just a matter of swapping them over. Like any sentence with 'just' in it, this foreshadows trouble to come.

The seller didn't have a good set of Aero wheel covers and since these are about 5% of the efficiency gain associated with this wheel swap, that was kind of important. A little more looking online turned up a set that just happened to be right on the way toward picking up the wheels. $50 for a nice set of four was pretty reasonable. We drove almost 100 miles to get the wheels, brought a brush and a tarp to try and not dirty-up the interior of the car too much. Yes, 4 wheels/tires fit in the back no problem.

Next up was tire selection. There's a lot of history regarding what works best out on the TMC Forums. Each brand, Michelin, Continental, etc. has their fan-boys and detractors. A couple youtubers had done reviews of a new brand of EV specific tires: Sailun eRange. These are made in Vietnam, mostly Chinese owned and are the OEM tire on some Chinese produced EVs. They are looking to make a name for themselves in the U.S. over the last year. It isn't quite as well reviewed as the EV tires from the 'majors' but they cost right at half as much. We'll see how it works out. The low cost (relatively reliable) supplier turns out to be Walmart. Very strange... But hey, $600 instead of $1200.

We know tires make quite the difference. A previous swap of worn Bridgestone EV specific tires for come cheap no-names ($80 ea.) on the Leaf that we turned back in at the end of it's lease period resulted in a 9% drop in range, just due to the tires. Same route, same temp. same pressure. 

Having tires delivered to Walmart Autocare was a new experience. All the high-end Tesla fanboys are losing their shit right about now. Guess they don't have $15K Teslas or live in our 'economic neighborhood.' ;-)
Mount and balance was quoted at $18/tire. and that seemed fine. We brought along the 'Lifting Pucks' that allow normal car lifts to jack up a Tesla without damaging the battery. Good thing too, or nothing would have happened. Walmart doesn't have lifting pucks -or- a car lift the goes low enough to fit under the Tesla. The guys there did have a low profile jack that would fit, on the lifting puck/adapter we brought, but that was only a partial solution.
The team there had to jack up one corner of the car, remove the 19" wheel, dismount the tire, remove the TPMS and replace with a new valve-stem, remount the tire, mount the TPMS on the 18" wheel, mount the new tire on that wheel, balance it, and put it on the car. Then repeat all of those steps for the four remaining corners of the car, since they only had the one jack. Along the way we agreed to pay for the Deluxe mount and balance. That includes lifetime rebalance, free tire rotations and 50K mile road hazard warranty. An extra $10/tire. Which sounds fine until you work out that they have no way to do tire rotations since that requires the car be on a lift and their locations can't do that.
...so they 'compromised' by refunding the entire mount/balance fee, and ended up with $0 for their labors.

Big corporations are weird.   Anyway, so how did it all turn out?:

Yes, it worked!  The previous tires on the car, a relatively cheap ($100 ea.) Ironman iMove Gen3 that Hertz swapped on just before selling (almost no wear on them) were not awful. Not seriously noisy, handling wasn't all that bad. the '380' treadwear indicator on the sidewall did not inspire high longevity expectations, but overall a kinda good average car tire.

Prior to going in for the tire/wheel swap we did our highway efficiency test loop. An out-and-back 20mi. each way plus a little on and off the freeway. ~41 miles total. 42 PSI Cold. 68 deg. ambient. 72 MPH (GPS) speed using autosteer on the freeway during a low traffic lull mid day on a weekday.
Results were 259 Wh/Mi.      

Since this is a route we do a couple times a week we can say 260 is right at expectations since we bought it.

After

After a short supercharge, we took it out for another test loop, 42 PSI cold, same distance, same roads, same GPS speed, 71deg. ambient and got a surprising result. 213 Wh/Mi.

We were expecting a difference of 25-30. We got 46.

The temp. difference could account for a little of it, but this was considerably bigger than expected.

Percentages are slippery, but you can look at this as an 18% improvement compared with the 259 number, or that "259 is 21% worse than 213" depending (as usual) on what point you're trying to make. Regardless it's nearly a 20% improvement.

Basically a 40 mile real world range improvement.

...and THAT is what we were looking for.

Our home electric rate works out to about three cents per mile. Supercharging averages around10-12 cents. 

At that rate it will take approximately forever to pay off the $1100 this swap cost us. 

However we're not done yet.

If the $1500 optional sport wheels and $400 worth of tires actually fetch $1000  on CL or FB-M then it will almost pay off during the first trip (which, 5000+ miles, is coming right up) but if they only fetch $600 then it will take longer, duh.

Either way we'll be using these cheaper 18" tires going forward and risking cheap wheelcovers to the gods of curb-rash. We kinda like the all grey stealth look, although there's others out there who will vehemently disagree.
Hopefully people with $1000 to spare.  ;-)

Notes: 

There will be more later on trip efficiency.

Yes they are maybe slightly quieter in the low frequency rumble range, but there seems to be a slight increase in the higher frequency range. 64db on our test road either way. They are slightly softer on rough roads, but you really have to be looking for it so it may be placebo effect.

There will.of course be commenters saying "It's all the wheels" or "It's all the tires" and "It would have been even better if you had just purchased product X."  Well no, neither just a wheel change nor just a tire change would stack up to 20%, but together....    And doubling the tire price for a 1-2% gain would be folly, at least economically speaking. Noise? Safety? more difficult to say.

One minor note, Before 74 indicated was 72MPH GPS. Now 73 indicated is 72 GPS. Suspect the difference isn't -quite- that large but it probably went from being off by around 1.8% before and more like 1.1% now, based on when we see the mph indicators change over.