Yes, but it depends on how much bigger you go. I you increase the tire size by one, but keep the same rim size it wont effect the speedometer much, like 1 or 2 mph. Chanhging rim sizes will change the mph. To fix this will be a pain in the butt, you will need to have the gear in the transmission changed where the speedometer cable hooks upto
yes your vehicle is set for a certain tire size because the speedometer tells how fast the tires are spinning so if you get bigger tires it will say you are going slower than you realy are and smaller vice versa