Going with my parents to get them new tires tomorrow. They currently have 225/75/15's. Their current tires look tiny and wrong for the truck. I was thinking about getting them 30/9.5/15's instead which is what i believe the truck had when they originally bought it used.
Can anyone tell me if the speedometer is fast or slow with the original 225's on. Don't have a way of testing.

Also would a tire like the Firestone Destination AT's be too much for the truck since it's only 2wd. My dad drives 60 miles a day on the highway and 10 or so on dirt roads in the desert. Eventually he might be moving where there will be some snow a few times a year.

 

The larger the diameter of tires you have over stock, the less times they will rotate, resulting in the speedometer showing that you are going slightly slower than your actual travelling speed. It is not very significant unless you jump from a 235 to say a 35" or 37"

 

It's quite easy to test your speedo on Interstate highway level road. Set cruise to 60mph that is one mile a minute yes?

Use the mileage marker posts and a stopwatch- you see what I mean? You hit a mile marker at 34 seconds into the minute then the next one should be at 34 seconds in again-have a passenger help out of course... do it for 5 miles straight and so on...don't make a judgement just over one single mile.

The Firestone Destination A/T would be a fine tire, I am considering the General Grabber AT2s, the Discount Tire guy pointed me at a Hankook RF 10, I see others run the Kumho KL78 AT.

Also WallyMart has some Goodyear Authoritys that have caught my eye if not my wallet. yet....

If your father favors the American manufacturers I always point out the Cooper Tires Discoverer models. They are based in Findlay Ohio- my high school alma mater. And tires are still built there....not sure if those specific ones are....