What changes when you go from this size to that size?
Enter your current tire and wheel spec, then the spec you're considering. Get the diameter change, clearance delta, offset/backspacing shift, and how far off your speedometer will read — drawn to scale, not just listed in a table.
Result
Your speedo reads 60 — you're actually doing —.
At 70 indicated: —
Clearance uses nominal section width, not measured width — a 285 is only 285mm on the rim width it's rated for; mount it on a wider or narrower rim and actual width shifts a few mm, so treat the number above as an estimate.
Why this includes speedometer error
tiresize.com, wheel-size.com, and willtheyfit.com stop at diameter difference and leave you to work out what that does to your speedo and odometer. A larger rolling circumference means fewer wheel rotations per mile, which means your speedometer under-reports — see how speedometer error works for the full explanation.