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Are my tires close enough to fit my daughter’s car?

I have a new set of four Pirelli P4 tires, size P215/65R16. My daughter has a vehicle that takes P215/70R16. I would like to put my tires on her car. I realize that they are a tad smaller, but would they still not work well and be just as safe? – Don

The size difference is too great.

The Pirellis are not necessarily smaller; the tread width is the same. The difference lies in the height of the tires. The difference in overall diameter is 2.15 cm or almost 10 per cent. The maximum recommended difference is 3 per cent.

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The height difference will be a problem because the suspension, steering and other components were all developed around the original equipment tire. The taller tires will turn 770 times per mile compared to 795 for the other and the speedometer will be off about four km/h at highway speeds.

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