Tow vehicle tire size not to spec

davehultin wrote:
I'm looking to replace the tires on my tow vehicle (2010 Ford Expedition) and I was surprised to learn that my existing tires do NOT match the tires specs on the vehicle placard. I don't know when or why that happenend. Anyways...

Placard specs are P255/70R18
Existing tires are P265/70R18

So my existing tires are 10 cm wider than what's specified. Is that a bad thing? Or just a "thing?"

My Expedition is no champ for gas mileage, but does that extra 10 cm per tire take the mileage down significantly?

In your opinion, should I return to specs when I replace the tires, or is there a compelling reason to stick with the wider tires?

Sometimes the OEM supplies wheels that are barely wide enough for the specified tires. That would mean that upsizing a tire might result in more center wear.

But that is not the case for your vehicle. It came with 8.5" wheels and a P265/70R18 can be used on up to a 9" wheel.

Fuel economy?

First, tire rolling resistance varies a lot between make/model - much more than mere tire sizing changes do!

Secondly, the 265 has a larger diameter which should help fuel economy.

Thirdly, Worn tires have less rolling resistance than unworn tires do - all other things being equal. So expect a loss of fuel economy when you change tires.