Hi everybody, I need your help to figure out something.

For road cars, for example, opel corsa 1.3cdti, it uses 175/65/R14 tires. The professional companies says there is a limit for difference when changing it, you can not change it if the value is +-%3. So it means I can not run with 195/65/R14 it will cause lost grip, weakness brake force and much more fuel consumption. Now I have to need learn how to calculate all of this physicals equation, more information for satisfaction

*It makes sense from 175 to 195, pressure will be reduced per unit area

http://www.1010tires.com/tiresizecalculator.asp

i think the 3% thing is more to do with the fact that if it exceeds that amount of difference then your speedometer will be inaccurate.

For something running 175/65/14 as standard id stick 195/60/14 on it, only 1.1% difference

If you increase the width or diameter, then you should decrease the profile to keep the same rolling radius which will keep the speedo accurate and make sure the wheels and tyres still fit in the arches of the car.

Who cares too much about how off their speedometer is? My car has 185/65r15 stock, but my summer tires are 205/50r15. It helps keep me from getting speeding tickets lol

Plus slightly lower gearing, handy for acceleration