i am looking in to getting new tires for the summer i think that i am going to go with the azenis just because of the price and good performance of the tire.
my regular wheel size is 185/65/15 and the size the have in the azenis is 205/50/15.
so my ? is do u guys think the change in profile and so on will change the rolling diameter of the car, will the change in tire make my speedometer to become off? any recommendations are welcome thanks guys.

 

To calculate rolling diameter, take 185mm (width of the tire), divide by 25.4 (mm per inch), multiply by .65 (sidewall height is a percentage of width...in this case 65%), multiply by 2 and add 15".

185mm = 7.28in (converting width to inches)
7.28in x .65 = 4.73in (calculating sidewall height)
4.73in x 2 =9.47in (x2...you have 2 sidewalls [top/bottom])
9.47in + 15in = 24.47in (total rolling diamter)

stock = 24.47in
azenis = 23.07in (supposed measurement at 205/50/15)
azenis = 23.66in (actual measurement is closer to 220/50/15)

Your speedo will be off. It will show you going faster than you really are because of shorter effective gearing. But the shorter gearing will give you better acceleration.

 

how would u be able to adjust the speedometer?