Tire size vs speedometer/odometer

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Oct 16, 2001 | 09:04 PM

fordtrucklvr

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Tire size vs speedometer/odometer

I recently purchased a 1997 F-150 4x4 ext cab. The dealership agreed to put 2 tires before delivery and I agreed to pay for the other 2. They tried to pass off Goodyear 225/70/16's which were way too small. They tried to tell me they could not find 235's due to the recalls...I then requested they put oversize tires. At the time I thought 255's, which they installed, were oversize since everything I read said 235's were stock, however my door lists 255's. Can I assume my speedometer gearing is set up for 255's if the door sticker lists these tires?

Oct 18, 2001 | 12:37 AM

gtex

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Joined: Apr 2001

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From: Texas

Tire size vs speedometer/odometer

It depends on the overall diameter of the tire. The 235 or 255 number is the width in millimeters. A 235/75r16 should be close to a 255/70r16 in diameter and would probably have little change on the speedo. A 255/75r16 is taller than a 235/75r16. The door tag is probably the best bet for accuracy. Just make sure to match the width and the ratio. I.E. 255/70r16 or 255/75r16.
Tire Diamter
235/75r16 = 29.0"
255/70/16 = 30.1"
255/75/16 = 31.1"

check out www.4lo.com for calculators or search this site.

Greg