You can see the differences here (which aren't that drastic on the 2 sizes you listed):
The best tire size calculator. Use our tire size calculator to find tire size specs and suggested tire sizes. Then check prices for all available tire sizes.
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just plug in both sizes then look to the right side that shows the changes in width, sidewall height etc, but also take note/beware of the speedometer variances that occur when changing the tire sizes on the same size rims....
For taller sidewalls or wider tires, AFAIK the main concern
on the front is whether the wider/taller tires will rub against anything on the suspension or frame when the wheel is turned. On the back, the main concern would mainly be clearance between the wider/taller tire & the fender wells...
Again, on those sizes you listed (65 to a 70), you're only talking about 1/2" to 3/4" difference in
height, but a change from a stock 265 to a 285
width would be significant, so please do your research first if that's the way you decide to go.