Tires: Toyota 4Runner tires, toyota 4 runner, toyota 4runner

Question
I have a 1998 Toyoya 4Runner. The original tires
on it were 265 70R 15. I purchased a new set of 255 70R 15s and put them on it. Since then I have noticed that the vehicle has to work harder to maintain speed. The RPMs at 55 MPH is running at about 1900. I have also lost an average of 4 miles to the gallon of gas. Is there a way to correct this or do I need to change the tires back to the original size. I did not hink that the size would change the performance of the vehicle this much.

Answer
Joey,

I think you have the tire sizes wrong.  According to my book a 1998 Toyota 4 Runner cae with either P225/75R15's at 29 psi front 32 psi rear or P265/70R16's at 29 psi front / 32 psi rear.  Check your vehicle placard and which it is.

In either case, the drop in tire size is 2% smaller in diameter and that would have to be factored into the fuel economy equation.

This also means the engine is running 2% faster for the same ground speed - the wrong direction for fuel economy.

But in case you got the rim diameter wrong and you now have P255/70R16's on it:  The original P265/70R16 had a load carrying capacity of 2216# front and 2326# rear, which eans you barely have enough load capacity for the fronts at 34 psi, and not enough load capacity for the rears.  This increases your risk of failure and tire failures can sometimes have tragic results.

Nevertheless the change in size was not the right direction.