The sidewall height of 165/70/R14 is: 70% x 165 = 116mm. and the sidewall height of 195/60/r15 is: 60% x 195 = 117mm. Hence the profiles of both the above mentioned sizes is exactly the same, the only difference is the rim size, hence resulting in an increase in ground clearance by 1-1.25".
R15x6j is the size of the rim, with 15 being the diameter in inches, 6 being the width of the rim in inches and J being the rim edge/tire bead profile.
It is very important to opt for the rims whose width best suits the profile and dimensions of ur tire.
Opting for a rim which is incompatible with ur desired tire profile, will result in a excess wear n tear of tires on road, and they represent a safety hazard on highways.
Let's take the example of OEM wheels:
the width of the tire is 165mm=6.5" and the width of the rim is 5" which is 77% of the tire width. The acceptable ratio is anywhere between 75% to 85%. Beyond 85%, you will have a relatively straight sidewall as opposed to a contoured sidewall, depicted in the pictures below:
Contoured side-wall offers more comfort for our pakistani roads.
ET is the offset of the stud plate of rims from centre line of the rim. The higher the ET value, the further it is from the centre line of the rim. If u select in appropriate value of the offset of the rim, u might end up either scuffing the tire with the suspension and wheel well every time u go over a bump or take sharp turn or u can also end up scuffing the tire edge with the fender lip.