speed recalibration

my friend just put seventeen inch rims on his car and is giving me his 185/60/14 that are practically new. my car has 185/65/14.
my question is will i have to recalibrate my speedometer if i get a lil smaller wheel? also how do you recalibrate a speedometer and is it hard?

Your original 185/65-15 tires are 23.5" while the 185/60-14 tires are 22.7" so there is 3.4% difference so that your speedometer will overestimate by 3.4% so if your speedo shows 60 MPH you're actually going 57.96 MPH. As long as you are aware of the amount of error you really don't need to calibrate your speedo . . .

If you have ABS which you probably don't the smaller diameter may cause issues . . .

If you run the smaller tire what is critical is that you run the smaller tire at 35 psi instead of the factory recommendation. This alllows you to have about the same load carrying capacity.

my tires are 14 inches not 15. so the difference is isnt that big is it? also what is the formula you are using to find the percentage difference?

I meant 185/65-14in my previous post If you run this size you don't need to recalibrate your speedometer. For information on how to recalibrate your speedometer I would check the Civic part of this site or other Civic specific sites.