Before I start I just want you all to know that I did use the search function and read through the posts trying to find an answer to my question. While there was a ton of info to read, none of it specifically answered my question, so here goes:
When I bought my 2002 Screw two weeks ago, it included Falken 285/60/18 STZ01 tires. The original tires according to the door jamb sticker were 275/60/17.
The questions I have are:

How much is my speedo off and should I have it recalibrated?

My odometer would be reading less miles driven, correct?

Would I be calculating more or less fuel consumption than actual mpg?

And lastly....is it something I should be concerned about, or no big thing?

Thanks for your help.

Reloader

 

th

 

Tire Size Calculator

You have about 5% error. Fuel mileage calculations would be 5% lower than you are actually getting.

 

The original tires would have a 29.99" Dia. with a circumferance of 94.22 inches.

The new tires would have a 31.46" Dia. with a circumferance of 98.85 inches.

This will effect more than just speed. It does actually effect milage even if you have the speedo recalibrated. Deepending on your gear ratio.

Example I have a 4:10 gear ratio with 245/70/17 and am changing to 295/70/17 Although I am not changing the gear ratio. my truck will now act like it has closer to the 3:73 gear ration actually someplace about 3:80 or so.

My truck will not run as high an rpm on the highway now, but will also tow a little harder, but still better than someone with the 3:55 or 3:73 gear ratio. So since the truck will run lower rpm i should in theaoy get better milage when driving (Without the trailer at least)

The dealer tells me the Speedo can be recalibrated, where mine will be off about 5mph at 55 and about 7mph at 75 it is alot for me. Yours should be less based on the numbers. someplace between three and four at 55mph.

Hope this helps.