Tires: tire size, ford f 150, narrow footprint

Question
I changed tires on my '06 F150 Ford 4x4 with a 5.4 engine from 275.65.18 to 325.65.18, more for looks than anything else.  I am hearing from my dealer that I may loose my warranty for that.  What tire could I put on that would keep in warranty and give me a reasonable 4x4 look?

Answer
Mike,

First, any time you change tires, the vehicle warranty may be voided.  The only way to be absolutely sure the vehicle warranty is never voided is to use the exact tire that came on the vehicle.

However, the warranty is probably not going to be voided for those items that would be unaffected by the tire change.  Clearly, keeping the same tire size would be a large help here.

BUT, a 2006 Ford F-150 came with 7.5" X 18" rims, and a P325/65R18 requires a minimum of a 9" rim.  This might lead some stability problems as the tire will arch across the treadface and have a long narrow footprint, rather than a short wide footprint.  This will tend to make the vehicle sensitive to side winds and the vehicle will tend to be sensitive to irregularities in the pavement.  Clearly the warranty would not cover any issues related to that.

Not to mention the speedometer error of 7%.  Clearly, any issue involving the speed of the vehicle - such as engine or transmission performance - could be affected.

I'm sorry to tell you, but the original tire size is the largest tire that is within the rim width's acceptable range.

I don't see any way that the vehicle warranty would not be voided for any performance related issue.