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19" and 21" on the same car

I will have my model S equipped with 21’’ wheels for summer tires and 19’’ wheels for winter tires. I guess the readings on speed and distance in the speedometer will be a bit off when I change the wheels in spring/fall. Can I set the size of the wheels in a setting on the car for the readings to be correct or is there a kind of sensor for this?

Not settings yet available to accommodate the different wheel size... the difference in speed and odometer reading should be very minimal.

It is called plus sizing. A 19" tire has a taller sidewall so the overal diameter is the same.

Tire Size Comparison
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
245/45-19 4.3in 13.8in 27.7in 87.0in 729 0.0%
245/35-21 3.4in 13.9in 27.8in 87.2in 727 0.3%
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Use the 'pre' tag for fixed font tables:

Tire Size Comparison
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
  245/45-19    4.3in   13.8in 27.7in    87.0in          729    0.0%
  245/35-21    3.4in   13.9in 27.8in      87.2in          727    0.3%

The only issue you will have is that for half the year the image of your car on the dash will have the wrong wheels on it.

I know - the horror.

When I got my Model-S last October, it came with the 21's and I bought a set of 19's for driving in the winter up here in Seattle. When I had them swapped out the image changes. The API has a setting for the tire type so I believe the tech's can change the setting in the internal config so that the car images match what your car looks like. Now, if you have aftermarket wheels, you are likely out of luck...

-Joe


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