You can change the diameter of the rim used to one of the 3 Tesla options (19, 20 or 21), which is used to adjust the estimate for miles remaining with the current battery state of charge. That's all it does, nothing more. It does not allow you to enter in any custom tire size or overall diameter, it assumes that you are using on of the 3 Tesla options that all result in the same 28.0 inch diameter, no matter if you select 19, 20 or 21.
If you install a tire that results in an overall diameter that is not 28.0 inches, then you will have speedometer and odometer issues, your Tesla will be over or under reporting. By how much all depends on how much that new tire deviates from the expected 28.0 inch diameter. Use this site to compare and determine.
Tire Size Comparison The Tesla defaults in the settings are:
- 255/45 R19
- 255/40 R20
- 255/35 R21
It is probably best to stick to one of these sizes but if you want something else, do your homework first and make sure it will work and you are okay with the outcome.