To what extent does changing from 14 inch to 15 inch wheels effect the speedometer/od

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nitronut

nitronut

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I changed the wheels on my ride from a 14 inch to a 15 inch rim. How much will that offset the speedometer and odometer readings?
 
depends on the actually change in circumference of the tire
that is why speedometer gear charts have tire sizes listed in inches, instead of tire sizes

so, if you can tell us what tire you are running now, and what you wish to replace it with, we can give you an answer
 
IF you go to a "plus 1" tire rim combo, the OD of the tire remains what the original tire was. Plus 2, 3 etc.
 
It's all in the percents.
A change in the tire by 5%, will change the speedo by the same 5%. It is most accurate to measure the tire roll-out.

The same goes for any correction. If you are traveling at an indicated 60mph, and come to believe that your true roadspeed is 66mph; that would be a 10% error, and requires a 10 % change it pinion tooth count.
 
Get a GPS speedo app for your phone.
 
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