Can i use 185 60r15 instead of 205 60r15 tires

 

Difficult to speculate without knowing what the application is but there is a major difference in tire height between those 2 sizes. If you're downsizing in tread width, it's usually best to maintain a similar height to minimize speedometer error. For example, a 195/65R15 will be closer in height to a 205/60R15 than a 185/60R15, plus you only forfeit 10mm of tread width.