They fit, no problem. I put two in the trunk, one on each of the rear seats. A couple things to consider:
1) Les Schwab changed my tires and reset the TPM's (Tesla double checked them a few days later to make sure it was correct), however, I reused the TPM's from the OEM wheels.
2) If the new wheels come with lugs specific to the wheel, use them! Les Schwab didn't see the lugs that came with my Rials and used the OEM tesla lugs...they did not seat right. It felt like the car had low profile tires. Once the correct lugs were swapped out, the ride was as good, maybe better than the OEM wheels.
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One more thing, if the aftermarket wheels are boxed individually, you may want to use the boxes for transporting your OEM wheels back home...