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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 | 2019年9月11日

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: https://tiresize.com/calculator/

gmr6415 | 2019年9月12日

@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 | 2019年9月12日

Patronus is correct.

wiboater4 | 2019年9月12日

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

spuzzz123 | 2019年9月12日

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

lbowroom | 2019年9月12日

Wheels yes, the tires mounted to them, no

don.lind | 2019年9月12日

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 | 2019年9月12日

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 | 2019年9月12日

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 | 2019年9月12日

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 | 2019年9月12日

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

lbowroom | 2019年9月12日

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 | 2019年9月12日

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 | 2019年9月12日

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 | 2019年9月12日

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

lbowroom | 2019年9月12日

Yes, you won't notice a difference.

TeslaTap.com | 2019年9月12日

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 | 2019年9月12日

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 | 2019年9月12日

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.

YUL X | 2019年11月7日

now that i have my winter rims on ( 22" to 18" ) i changed the rim size on the computer, now i have many error codes since it rebooted. emergency braking disabled. regenerative braking disabled. etc how can i fix this>?

Bighorn | 2019年11月7日

Some winter tire choices have messed with the regen because of squirreliness from the siping. Unlikely related to changing the diameter choice on the computer.

YUL X | 2019年11月7日

after several hours and a reboot, the car systems changed and all is ok.

lbowroom | 2019年11月7日

Yul X. running 22" wheels, I'm thinking that you don't have a model 3, correct?

FISHEV | 2019年11月7日

In the tire shop today and ordered Micheline Xice3 245/40/18. Tire guy said this will give a slightly wider profile and some rim protection (about 3/10") and slightly smaller diameter so car will overstate speed and distance by a small fraction, 2.3%.

Be nice if Tesla allowed for recalibration based on tire size as well as wheel size.

lbowroom | 2019年11月7日

They offer preset correction for the tire and wheel combinations they offer for the vehicle. All calibration is based on rolling diameter of the tire, wheel doesn't really matter. They reference them by wheel size in the menu as that's how people identify the packages the easiest. All 3 Tesla wheel packages are fairly close to the same in rolling diameter. All rolling diameters vary with tire pressure and wear.

Syed.Hosain | 2019年11月7日

The best way to compare speedometer change is by using revolutions per mile (info is on Tire Rack) for the tire.

For example, a Michelin Pilot Sport 4S 235/45-18 is 890 rev/mile; the 245/45-18 is 880 rev/mile and the 255/40-18 is 899 revs/mile.

Since my speedo was in error anyway for the stock 235/45-18 (Michelin Primacy MXM at 880 rev/mile) compared to a GPS speed app, by about 1 mph at 60mph, the best fit to correct that was 245/45-18.

However, I wanted more rim protection, so went with 255/40-18 a few weeks ago. So my speedometer is off by just under 2 mph, (actual is 58 at an indicated 60). Not a bad trade-off at all, as far as I am concerned.

Syed.Hosain | 2019年11月7日

Of course, all the above would be at 45 psi settings at new tread depth.

lbowroom | 2019年11月7日

I wouldn't be surprised if the wheel selector is just used to change the graphic of your vehicle to reflect the correct wheel package.

FISHEV | 2019年11月7日

"The best way to compare speedometer change is by using revolutions per mile (info is on Tire Rack) for the tire."@Syed.Hosain

https://tiresize.com/comparison/

You can plug in your current tire and new tire and see all the differences and performance consequences. Going from the 235/45/18 vs. 245/40/18. I'd be going 58.6 miles an hour but Tesla will say 60 mph.

Syed.Hosain | 2019年11月7日

@FISHEV

That tire size comparator (like others of its type) is too simplistic. It uses basic calculations only based on the tire size you input.

However, the exact same size tires - typically *between* brands - can actually have slightly different speedo values because of quite different section profiles, etc.

The *correct* way is to use revs/mile to see the likely speedo error.

FISHEV | 2019年11月7日

"That tire size comparator (like others of its type) is too simplistic. It uses basic calculations only based on the tire size you input."@Syed.Hosain

It does what it does, compare tire size and the driving consequences.

The performance comparison between the tires is an entirely different data set and it takes a Consumer Reports or other testing company spending millions to do the tests year after year with solid test metrics and standards.

Once I know the tire size consequences, I can move on to which tire. I've used the Xices and had no MPG changes on the Subaru which also had OEM Michelins.

The calculator says speed consequence as noted above, 766 rpmile vs. 785 rpmile for the Xices.

lbowroom | 2019年11月7日

All of it is “in the ballpark” and good enough

Bighorn | 2019年11月8日

You want to go with narrower snow tires to cut down through the snow to the pavement. Never go wider. Better to have more sidewall as well—minus 2 fitment is common on Performance models.

FISHEV | 2019年11月8日

"You want to go with narrower snow tires to cut down through the snow to the pavement."@Bighorn

In theory yes, in practice it doesn't really matter in the differences between 235/45/18 vs. 245/40/18. Same is true for all minor variations in tires size the car can handle. And 90% of winter driving is on snow free roads so you don't want to compromise safety for 90% of your driving for an imperceptible difference in 10% of the snow driving.

In ice driving, snow packed ski resort roads, you actually want a larger footprint for traction on the ice so the larger tire is better in the most challenging of winter conditions, glare ice.

nick.kahl | 2019年11月8日

Anyone know how long to wait for delivery of 18" Areo winter tire package?

Syed.Hosain | 2019年11月8日

@FISHEV ""That tire size comparator (like others of its type) is too simplistic. It uses basic calculations only based on the tire size you input."@Syed.Hosain

It does what it does, compare tire size and the driving consequences."

"Driving consequences"? How does a simplistic by size calculator give you that? What does that phrase mean in this context?

I can show you different brands/models of tires that *at the same size* have different speedometer readings due to the revs/mile being different.

So, still better to use revs/mile *if* the speedo error matters to you. for me, once I know what it is on my car (almost 2mph off at 60) I just mentally take that into account and proceed without any further issues.

FISHEV | 2019年11月9日

"Driving consequences"? How does a simplistic by size calculator give you that?@Syed.Hosain

If you go to the link and look it gives all the performance differences between the two tire sizes such as speed consequences of diameter change, width changes. My reason is to gain tire sidewall protection for the rims as the 235/45/18 lead to scraping the rims while the 245/40/18 will stick out 0.3" more. The local tire shop said it has a built in rim protector bead also, hoping his right and it adds more rim protection.

"once I know what it is on my car (almost 2mph off at 60) I just mentally take that into account and proceed without any further issues."@Syed.Hosain

I'm hoping there is some way to calibrate the Model 3 speedo. Do any of the preselects come close?