Reading your tyres, i've read through a fair few forums and found alot of people get this wrong. Alot will understand, but for you who are unsure, or just dont know heres how.
195This is the width of the tyre in mm. Looking at the tyre from above or from a forward view.
45The ratio of the height of the tyre (profile). A percentage of the width. 45% of 195mm is 87.75mm
15The wheel diameter in inches.
78Load Index. Weight in which the tyre can withstand. Measured in Kg the number's are set by a table which will tell you the capacity of the tyre
VSpeed rating of the tyre. The letter is set by a table which will tell you the speed rating of that spacific letter.
Load Index
Speed Raiting