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Spare Tire Size Discrepancy Lincoln LS V8 Sport Package

The recommended tire size for my Lincoln LS 2001 V8 Sport Package is P235/50R17. Tire size recommended for the V8 without the sport package is P215/60R16. My full size spare tire that came with the vehicle new (eons ago) is P215/60R16. I have the 17 inch rims on the car. Is this a problem? Do I need to replace the spare?

The circumference of your regular tire is 82.46 inches (or less as the tire wears). The circumference of your spare tire is 82.15 inches. I assume this is close enough not to cause a problem.

No, you don’t have to replace the spare. Your spare is the same diameter as the 235/50/17 tire and wheel. In the aftermarket wheel world they call this a “Plus 1” tire and wheel package. The original rim is 16 inches but the tire is a 60 series model. That means the distance from the rim to the tread is 60% of the “215” millimeter width. Multiply that times two and convert to inches (divide by 25.4) and add to the rim diameter and you get the tires total height. The 235/50 is a 50 series, or 50% of 235 mm. That number is smaller so when the additional inch of rim diameter is added in, the total tire height is pretty much the same. Treat it like a temporary spare. The tread is narrower, like those mini spares they use in a lot of cars, so it should be used to get you to a tire repair place to get the 17 incher fixed. It makes a perfect spare, keep it unless you want to do a five-wheel rotation.