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My speedometer is off about 5mph at 75 it reads 80. According to the glovebox the tires are the correct size. Is there a chance that the previous owner changed the gearing in the pickup when he went to larger tires for awhile and then back to originals? He told me he didn't change anything but I tried changing the sensor and that made no difference. Also saw the same exact car to mine yesterday and it had 14" tires on it whereas mine are 13" Any help will be greatly appreciated. If anyone knows the formula for tire size change vs speed indication that would be great also. Might just try to find some used steel 14" instead.