Examining Range Impact For Various Tesla Model S & X Wheel Sizes

Tesla

SEP 14 2016 BY STEVEN LOVEDAY 38

Tesla Model S

Tesla Model S

While range is only impacted marginally by wheel and tire choice on the Tesla Model S, the Model X is a different story. Particularly, the wheel diameter may change range by ten to fifteen percent.

Tesla Model X

Tesla Model X

It seems range is scrutinized and analyzed more with electric cars, likely because range is a main focal point in the segment. Not as often do we see or hear about ICE vehicle owners painstakingly calculating their change in gas mileage based on a tire purchase or wheel upgrade. Of course, there are surely those that make it a priority nonetheless.

On Tesla’s site, the Model S page features a cool range calculator.

When switching between 19-inch and 21-inch wheels, the loss of mileage, is around 5-6 miles per charge for the lower models. Once you get up to the 90 series cars, the change is a bit more, but still not drastic. The P90D sees a drop of about 13 total miles of range.

So, the typical 2-4% range drop from wheel size is about half of the 7% range gained per battery upgrade. The upgrade to 21-inch wheels costs $6,000 and the battery upgrade from 70 kWh to 75 kWh costs $3,000.

Unfortunately, there is no nifty calculator on the Model X page, but one might assume that the results would be similar given that the cars are siblings. However, the Tesla Design Studio informs that upgrading to the 22-inch wheels from the standard 20-inch wheels results in a range loss of about 40 miles!

With this information available, consumers should seriously consider the added cost of wheels and the subsequent loss of range, when designing their Model X. While looks may be very important to some buyers, upwards of $16,000 between the wheels and the range loss – nearly three times the cost of the wheels alone – may be a hard pill to swallow.

Source: Teslarati

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38 Comments on "Examining Range Impact For Various Tesla Model S & X Wheel Sizes"

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A graph or chart would be nice to go with this information.

The torque vs current graph is a quasi-exponential graph. The electric motors suck up too much power on low RPM, the sooner you get them working above 30% of their -no load- maxRPM capacity the more the current draw drops.Also the highest torque occurs within that initial 30%. The larger diameter wheels make the cars work at a lower RPM rate at constant speed, therefore increasing slightly the current draw reducing the range (even with the increased capacity pack.)

It’s not actually 19” vs. 21” wheels, but in reality just 19” vs. 21” rims.
This doesn’t tell anything about the overall wheel diameter. In fact larger rims user tires with lower sidewalls, so the wheel diameter practically stays the same regardless om the rim size.

Original Model S 19” rims use 235/45 R19 tires, while their 21” rims use 245/35 R21 tires.
For 245/45 R19 tires the overall wheel diameter is 27.68”
For 245/35 R21 tires the overall wheel diameter is 27.75”

Difference: 27.75” – 27.68” = 0.07”
Percentage difference: 0.07” * 100 / 27.68” = 0.25%

A mere 0.25% larger diameter is not what causes a 2-4% range drop.

Tire calculator to compare dimensions for two different tire sizes: http://www.discounttire.com/dtcs/infoTireMath.do

If you want to do your own calculations you can use the formulas at this page instead: http://www.discounttire.com/dtcs/infoTireMath.do
They will give you the exact same result.

Made a typo, it should have said 245/45 R19. But the calculations are based on the correct dimensions.

Sorry, I posted the same link twice. The second link should have been: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=7

The problem is for top speed bragging rights they lose a lot of range vs gearing for 100mph or less would increaze range 50 miles or more.
While I appreciate top speed it should be optional to have higher number gearing for those who will never go over 100mph and want the generous benefits of longer range, better towing, faster acceleration , etc it gives.

Yep it’s true. Win win situation for me because i didn’t have to spend $5k plus on the other rims. And the 20s look good still.

I was thinking of upgrading my wheel on my model S to 20″ from 19″. I wonder if model X wheels would fit.

Are they taking into account the weight of the wheels. A lighter wheel would require less energy to get rolling and keep rolling.

For lucky owners of 1972 MG Midgets with wheels/tires of 145/13 vintage these variables are well known as well as the variation on the speedometer.
Very good article

The Model X configuration lets you pick 22″ or 20″ and it shows 10%-15% difference. Lot of realworld feedback confirms 10% or more is very true.

Configuration:

Does that infer that smaller wheels on the BMW i3 would result in more range?

Yes definately

Is it the aerodynamics or diameter of the tires that are making the difference?

The tire diameter is practically the same for both rim sizes.

It’s not actually 19” vs. 21” wheels, but in reality just 19” vs. 21” rims.
This doesn’t tell anything about the overall wheel diameter. In fact larger rims user tires with lower sidewalls, so the wheel diameter practically stays the same regardless om the rim size.

Original Model S 19” rims use 245/45 R19 tires, while their 21” rims use 245/35 R21 tires.
For 245/45 R19 tires the overall wheel diameter is 27.68”
For 245/35 R21 tires the overall wheel diameter is 27.75”

Difference: 27.75” – 27.68” = 0.07”
Percentage difference: 0.07” * 100 / 27.68” = 0.25%

A mere 0.25% larger diameter is not what causes a 2-4% range drop.

Tire calculator to compare dimensions for two different tire sizes: http://www.discounttire.com/dtcs/infoTireMath.do

If you want to do your own calculations you can use the formulas at this page instead: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=7
They will give you the exact same result.

Assuming Peter is correct, that the actual tire diameter is practically the same, then there must be some other factor affecting range. The amount of tire flexing is a significant factor; tires which don’t flex as much don’t waste as much energy, yielding longer range.

Another factor is weight. The more weight near the edge of the wheel (the rim plus the tire, not just the rim), the more energy is lost from acceleration/deceleration. Do the larger rims put more weight near the outside of the wheel? Obviously, all other things being equal, a larger diameter rim will weigh more. But a lower profile tire weighs less… I don’t know enough to understand how the different tires and rims would affect the equation.

Aerodynamics of different rims could also be a factor, altho I question it’s as big a factor as people who want to sell you custom rims want you to believe.

If the 21” versus 19” implies a smaller internal section of the tire, as it indeed does if the overall Wheel height is the same, then the air movement inside the tire will be more difficult when it has to move because of the compressed zone movement. That could be part of an explanation for the lower range with 21” versus 19”.

The larger diameter wheels are heavier. And to a small extent the larger diameter tires have more rolling resistance. But 98% of the cause is simply the wheels are heavier.

some imply weight of the tire may make a difference. So if you ride with your wife and dump her out you will get more range. I don’t think so !!!

Mhmm when my wife exits the car and i am on my own range always goes down… wonder why 🙂

To add to the story, if one is concerned with costs, a 19″(Model S)/20″ (Model X) tire will almost always be less expensive than a 21″/22″…If you’re willing to shop outside of Tesla, odds are significantly higher that a shop can mount 19″/20″ rims vs 21″/22″ allowing you shop to around…

Now to the impact…Even on the Model S config, all except the P100D state it comes with all season tires while the P100D, regardless of size, includes summer only tires…Diameter/width/weight/tire compound all can make big differences…

So why does the range go down? Increased rolling resistance? More torque required to turn the larger wheels?

We did an experiment in college physics addressing this. We rolled a round wood block and steel hoop of identical weight and circumference down a ramp. The round wood block accelerated much faster.

The larger a circle or the farther out the weight is concentrated, the more torque it takes to accelerate.

A larger diameter wheel of the same width should have less rolling resistance.

You mean, a smaller diameter wheel of the same width should have less rolling resistance…. all other things being equal.

But a lot of other things here aren’t equal at all. Rim diameter and weight distribution, tire height and weights, and rim aerodynamics, are all different for different rims and tires.

Frankly, I hadn’t even considered tire/rim width. If the larger tires are wider, and have wider rims, then that is almost certainly the most significant factor. Wider rims would put more weight at the outside of the wheel (wheel = rim + tire), increasing rolling resistance and lowering range.

The 21” will indeed have more inertia than the 19” ones because mass is further from the center. But inertia has normally no effect on energy consumption.

sure it will. It is just like the fact that a heavy car takes more energy . . . but only because of stop & go driving. More force required to accelerate.

I have 21″ wheels on my Model S. It’s easy to crack a rim with the low profile tires. I would know. I just had to replace the right front rim. I found a reconditioned one for 750$.

I’ve heard a lot of negatives on the smaller wheels but never any positives. Just what are the advantages of going to larger wheels?

Better handling due to less sidewall flex.

Smaller wheels on the Model X have a higher tow weight rating, so that’s one difference. But probably only important if you buy the tow package. A post at the Tesla Motors Club forum says “…if you get the 22s you can only tow 3500#”, less than the full 5000 lb. tow limit for the MX.

One thing I wish Tesla would consider is 19″ grey turbine wheels. I don’t want the huge blingy 21″ rims, but chrome rims look very dated.

I hope they offer black or grey 19″ rims on the Model 3.

Smaller Wheels means less metal more rubber and air to rotate for the same overall diameter therefore bigger wheels means less air and more metal and that’s what makes them less efficient than the smaller Wheels

If those are lightweight alloy rims, then I’m not sure the weight difference between metal alloy and rubber tire is all that great. But if the nominally larger tires are wider than the nominally smaller ones, that means both the rims and the tires are wider… which certainly would mean more mass for the larger rims and nominally larger tires, and thus more rolling resistance.

Found a relevant post on the Tesla Motors Club forum:

[quote]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Weights:
19″ Wheels: 13.74kg ~30lbs each (according to a Tesla engineer)
Tires: 27lbs each (according to Tire Rack for Eagle RS-A2 245/45 19″)”

21″ Wheels: “the 21″ wheels with Continental ExtremeContact DW tires weigh 61 pounds. Tirerack says those tires weigh 26 pounds, so the 21″ wheels must be 35 pounds. ”
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

https://teslamotorsclub.com/tmc/posts/269624/

Citations given in the linked post.

* * * * *

Assuming the above figures are correct (looks like some guesswork or estimation there), then:

19″ tires + rims weigh: 27 + 30 = 57 lbs

21″ tires + rims weigh: 26 + 35 = 61 lbs

However, I don’t think that estimated 4 pounds of difference is the whole story, and quite possibly not the most important factor there. With low-profile tires, more of the weight — both of the rim and the tire — would be nearer the outside, which again would increase the rolling resistance.

The wider 21″ tires (8.5″ vs 8″) may also be an aerodynamic factor, altho a minor one. I note the BMW i3 uses narrow tires, presumably because those have lower wind resistance; slightly wider tires would have slightly higher wind resistance.

This is a bit out of the energy consideration but there is also another element on wheels and tires that is noteworthy.

They always consider rims size but the other important part of a wheel is the size of the sidewalls. The larger the sidewalls the more comfortable the ride and the more resistant the car will be to potholes. Those are two very important parameters, so in order to increase the size of the sidewalls while keeping a good grip in turns you need to larger tires as well.

Sidewalls size is often neglected and tends to be ridiculously small with almost the rubber directly on the rim and no air at all while the air is exactly what gives ride comfort and save the wheel in case of a pothole or other obstacle on the road like a stone, a brick or a piece of wood.

So instead of hesitating between 19” and 21”, I would rather like the choice between small sidewalls 19” or large sidewalls 16”.
So that is:

245/45 R19 0,703 m wheel height

245/60 R16 0,700 m wheel height

There’s a number of reasons why a 16″ tire wouldn’t work on a Model S, namely that it would probably be physically impossible to size a brake large enough to fit the wheel clearance, the sidewalls probably wouldn’t be strong enough to support the weight and performance requirements, and they’d look terrible on a performance car.

I am another supporter of tall side walls. Transport trucks have tall side walls with no load problems. I expect a tall side wall is aerodynamically good as was; the taller the side wall is closer to a disk.

Of course if larger side walls also give even less energy consumption then it really is a win win.

On esthetics I don’t have the impression that Formula 1 tires are unaesthetic at the contrary.