How to match tyre-wheel width

My car is currently using 205/60/R15 tyre dimension (standard from production). Can I fit 225/55/R15 to the existing sports rims? I heard that you can go up to +20mm wider without having to change the rims...:rolleyes:

There is no fixed formula but most 225/55-15 tires will accept a rim from 6 to 8 inches. Your rim with is often molde in very small letters on the outside of rim or it may be on the back of one of the spokes.