almost impossible to find used
Can I upgrade to 15" rims/tires?
What do I need to do?
Certainly. As a matter of fact a 15 inch tire and rim combo was a factory offering on most year models of the Mazda pickup. But it does matter a bit which trim level truck you own. If you have B2300 you will what to hunt for 225/70-15 sized tires, or if you have a B3000 look for 235/75-15 tires. Either can be mounted on 15x7 rims with a 5-114 bolt pattern.
Any decent tire store can tell you what will fit and what won't. You can't go too much bigger or it will throw off your suspension geometry and your speedometer reading. But many people go up one tire size with no real issues.
Put Michellen tires and your good.
I don't know what year your Mazda is but it is the same as a Ford Ranger .My 2000 Ranger with a 2.5 engine and automatic transmission has 225-75-15 tires from factory.
I see no reason you can't put 15inch rims and tires on your Mazda.Match the tire diameter as close as you can and the computer will never know the difference and your speedometer will be very close to being correct.
Good luck.
My Mazda pickup takes p225/70r14 tires
almost impossible to find used
Can I upgrade to 15" rims/tires?
What do I need to do?
