Does new wheel size selection option effect odometer?

Does new wheel size selection option effect odometer?

Just downloaded 2019.32.2.1. This update has a new option under 'Service' to select wheel size (18", 19", or 20") ostensibly in case you have changed your wheel size. The description says the setting will effect range estimation calculation. I wonder if it also effects the odometer... If someone has say 20" wheels, can they change the setting to 18" to trick the odometer to under-read and increase future resale value? Anyone care to do a test on a measured [long] distance to see if this trick would work? (ie on say a ~100 mile trip that is done repeatedly, one day do it with the setting at 18" and another day do the same trip at 20" setting and see if the odometer measures a different distance)

Patronus | September 11, 2019

Not if you do it right. Outside tire diameter is what matters, not wheel size.

You can play with different sizes using a tire size calculator:

gmr6415 | September 12, 2019

@bengarlick, with all the built in technology in Teslas do you really think they would be stupid enough to leave a loophole where an owner could intentionally reset the wheel size to the incorrect size and in affect extend their mileage warranty?

I don't think so.

I'm interested to know what the update does. As long as I've had mine (8/18) there has been a selection for wheel size.

stevehendler | September 12, 2019

Patronus is correct.

wiboater4 | September 12, 2019

I guess you could check your speed with another GPS to see.

spuzzz123 | September 12, 2019

So are you guys saying outside diameter isn’t different between 18 and 20 inch wheels?

lbowroom | September 12, 2019

Wheels yes, the tires mounted to them, no

don.lind | September 12, 2019

As the wheel itself gets larger, the sidewall on the tire gets smaller. That is, larger wheels require lower profile tires. The wheel itself plus tire still needs to fit in the wheel well.

coleAK | September 12, 2019

I’ll add, if you stay with the OEM outside diameter all is the same. But you could change that. With off road rigs it’s common to go to a larger outside diameter tire but with performance cars, especially in auto cross it’s common to go to a smaller outside diameter tire.

spuzzz123 | September 12, 2019

don.lind | September 12, 2019
As the wheel itself gets larger, the sidewall on the tire gets smaller

Wow. Had no idea. So other than the aesthetic, does the larger wheel size change performance or efficiency or anything(not counting the aero caps of course)? If the road/surface area on the tire is the same I would think they would perform similarly.

Patronus | September 12, 2019

The height of the sidewall has a dramatic effect on turning responsiveness, especially on initial turn-in. Smaller sidewall is better in this regard.

Conversely, a smaller sidewalls act as less of a spring (rougher ride) and are more prone to allowing wheel damage from potholes.

spuzzz123 | September 12, 2019

Forum education at its finest! Thanks all I’ll go to bed a little smarter than when I woke up

lbowroom | September 12, 2019

Wheel diameters grew to allow larger brakes to fit in stock racing series. Since the fender size was fixed, the rolling diameter of the tires had to be maintained, therefore tires became lower profile. This spawned an industry for performance low profile tires with stiff sidewalls and sticky rubber. So yes, low profile performance tires have better performance than cruising tires will tall sidewalls.

However, a short sidewall isn't required to be high performance in a car that isn't constrained by fender size. Take a look at formula 1 sidewalls, they don't follow that paradigm.

tucsonsims | September 12, 2019

The outside diameters do vary slightly between the three different rim size options. There is a 0.6% difference in o.d. between the 18" and 20" wheels:

235/45R18 = 26.33"
235/40R19 = 26.40"
235/35R20 = 26.48"

lbowroom | September 12, 2019

Yes, based on nominal tire sizes. Specific tire model, temperature, pressure, and wear have more variation than that though. I assume Tesla may down-rate the range based on the stickier compound on the 20's vs the 18's.

davidraph | September 12, 2019

I have 18in wheels, if I select 19in, but keep my 18in on my car. Will it work?

lbowroom | September 12, 2019

Yes, you won't notice a difference. | September 12, 2019

The reason Tesla has a selectable option 18/19/20" is to compensate for the range. The 18" will get the best range, and the 20" the worst. So if you want the longest range and highest efficiency, use the 18" tires. You can toggle through the options to see the effect on your range, ideally when SOC is near full.

I also assume this is based on the recommended tires. For example, you could replace the stock 18" LRR (low rolling resistant) tires with an 18" non-LRR tire that would have reduced range. In this case, the range would be overstated.

lbowroom | September 12, 2019

TT - I agree it should do that. However, I changed the wheel settings and my predicted range didn't change. At least not instantaneously.

douglas_peale | September 12, 2019

Larger brakes dissipate heat faster, and have more leverage allowing them to apply more braking force with less hydraulic pressure. To fit larger brakes on a car, a larger wheel is required. To fit a larger wheel in the wheel well, a lower profile tire is required, keeping the diameter of the tread the same. Metal is much more dense than air and rubber, so the larger wheel + low profile tire is heavier than the small wheel high profile tire. Larger brakes are also heavier. Brakes, wheels and tires are all unsprung weight (weight not supported by the springs) Lower unsprung weight results in a smoother ride, and the tires doing a better job of staying in contact with the road. So larger wheels are a trade off, you get better braking an turn response, but worse ride an less traction on a bumpy turn. (race tracks are usually smooth, so the less traction is not so important on a track).
Larger wheels also move the mass further from the center of rotation, so it takes more torque to get the wheels spinning. This slows the cars acceleration down a bit. Yet another trade off.
A lot of people buy large rims and low profile tires for looks, and leave the brakes alone. It looks ridiculous to me to see a huge gap between the brake caliper and the rim.