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My Malibu ls has 215 55r17. My friend crashed thier car with new tires. Thier tires are 215 50r17. Will i have any issues using that size tire. I has Steel wheels with hubcaps
 

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Note: All sizes are approximate and/or rounded. Pi = 3.14.

They will be slightly smaller in overall diameter, but only by a small amount. The 50 and 55 in the 2 sizes are the aspect ratio. That means that the sidewall is 50% or 55% of the section width, which is the width of the tire at the widest part of the bulge in the sidewall (not the tread).

So, 50% of 215 is 107.5 mm, and 55% of 215 is 118.25mm. The overall wheel diameter is 17" or 432mm. Add the sidewall height 2 times since we're talking diameter and not radius, and you get:

432 + 107.5 + 107.5 = 647mm.

432 + 118.25 + 118.25 = 668.5mm.


The overall diameter (times) Pi is the overall circumference, or how far you get on one rotation:

647 * Pi = 2031.58mm, or 2.03 meters per revolution.

668.5 * Pi = 2099.09mm or 2.10 meter per revolution.

The distance you travel on the smaller tires will be 0.07 meter or 70mm less, and this translates into a mere 3% difference.

Applying that 3% to your speed of 60 mph on the stock tires and you'll be showing 60 on the speedo but travelling at only 58 mph, a miniscule 2 mph difference.

On top of that, different manufacturers indicate their tire sizes and they're different in actual size compared to other tire manufacturers. Sometimes they're even different from other models of tires by the same manufacturer!


My vote is not to worry about it, and so long as both tires on the driven axle (front wheels for FWD) are the same or very close, it won't make any differences that you can readily tell.
 

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My front tires are 225/50r17, no issues at all. I got those when the standard 215/55r17s were unavailable and apparently it shows in their computer that those tires would work just fine on the car as well. So far they haven't failed me so I'd say you should be safe!
 
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