need sojme help have a 01 stock ranger with 245 75r 16 will 255 75 16 change the speedo which part of the tire changes the speed was told all 16 would be the same but othersay that hight not vwith changes the speed

 

the speedo will be off by about 2%.
you should be fine.

 

not all 16s are the same.

it will depend on the diameter of the tire, which can be calculated based on the dimensions written on the sidewall.

245 75 16 means

245: tire width, 245mm
75: aspect ratio, 75% of width, or 183.75mm
16: wheel size in inches

the diameter of your tire will be:

245 x .75 = 183.75mm = 18.375cm/2.54 = 7.23in.
7.23in x 2 = 14.46in.
14.46in + 16 = 30.46in

Change any of the numbers and your diameter will change, also affecting the speedo in a certain way.

 

I changed from 245's to 265's. It changed my speedo a good 3-4 MPH's slow. So the speedo would say 70 and actually I was going about 73-74. My xcal 3 cleaned that right up!