NEED HELP FAST GOING TO GET TIRES TODAY

[jimberg]

Okay, if 245 is the width you're after, I don't think you'll have problems. All cars are different though. Make sure that the aspect ratio will get you the correct height tire.

For example:

Stock '89 gts have 225/60-15s. I needed to go to 17x9" rims and I wanted a width of 245. Figure height with the following formula:

( Width * Aspect Ratio ) / 1270 + Wheel Size = Tire Height

( 225 * 60 ) / 1270 + 15 = 25.62

Now that you have tire height, plug it into the following formula to determine aspect ratio using new wheel:

(1270 * ( Old Tire Height - New Rim Size)) / New Tire Width = Aspect Ratio

(1270 * ( 25.62 - 17 )) / 245 = 44.68.

45 is the closest, so I picked 245/45ZR17s.

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351W 89 Mustang GT Convertible

[This message has been edited by jimberg (edited 05-07-2001).]