Modern Spare Size Question

[drb116]

Sorry if this has been discussed. I searched and could not find an answer on this.

I own a MY and a M3. The MY is used for longer trips and the M3 is generally only used around town and maybe a local trip up to 60 miles.

I am considering getting a Modern Spare for the MY and I know the M3 uses a different size tire, but I am wondering if the MY spare could be used for short distances on the M3. I am thinking something like 15 to 20 miles off highway to get it home in the case of a flat locally.

I am assuming the tire size difference will not be a big deal for a short distance, but I am not a car guy, so I don't know if anyone else can weight in on this.

 

[KenC]

Well, it helps to know what size tires we're talking about:

So, same bolt pattern, but the Y wheel is 1.2" bigger in diameter, or about 4.5% bigger. Generally less than 1% difference is ideal, but up to 3% is acceptable. Don't know about 4.5%. I'd worry that the car would find the wheel size mismatch to be too great and just keep stopping.

Why not jack up both the 3 and the Y, and take off one wheel and try it. Then you'll know for sure.

 

[jackmott]

While you can probably find a size that fits both, Tesla traction control can get pretty haywire if one tire is too far off on diameter from the others, so you might not want to try this.

 

[RickCRNA]

I also have a 2021 Model Y (19 in tires) and 2022 Model 3 (18 in tires) and had the same question. I bought a Modern Spare for the MY for road trips and when I acquired the M3 I called Modern Tire to see if I could use same tire for both cars since I also wanted to use the M3 for road trips. The answer was no since there is to great a difference in size spare tire between the MY and M3. I also read it’s possible to use spare tires from other vehicles, but in the end, each Tesla has its own Modern Tire spare. Glad I went with this decision.

 

[android04]

If you want to share a spare, you can try to find one with the same bolt pattern that is around 37.1" in diameter (halfway between the two). That would reduce the chance that traction control will go crazy in a short distance, slower speed drive.

 

[KenC]

If you want to share a spare, you can try to find one with the same bolt pattern that is around 37.1" in diameter (halfway between the two). That would reduce the chance that traction control will go crazy in a short distance, slower speed drive.

Genius! If you went halfway, you'd get a diameter of 27.1", or a 145/80/18. That puts you at 3% different to the Model 3's OEM size, and 3.3% different to the Model Y's OEM sizes. Supposedly acceptable, but one would have to try it to be sure the car's electronics don't have a fit. I wonder if you add air to the 3's other 3 tires, would it help, and reduce air in the Y's other 3 tires, to reduce the size differential.

 

[RickCRNA]

OP….save yourself from all this trial and error rigamoroll and just get another Modern Spare and be done with it. By the time you go through all of this nonsense and worry about what fits and inflating/deflating tires you could just have gotten the right tire in the first place.