question for someone smarter than me

so i have a stock 2017 trd sport. i recently bought some FX wheels off of Dustin and now have a set of Goodyear TrailRunner At's in 265/70/17. If i did my research right, the factory wheels weigh about 28 pounds and the factory toyo tires weigh about 36. the new wheels weigh 24 pounds and the new tires weigh about 38. i've lost about 2 mpg since i've switched. since the tires are a size bigger, would that affect my mpg that much or am i missing something. i'm very confused why my mpg went down so much. my typical drive, i average right around 19mpg, it's now down 17 or so.. thoughts?

 

Tires one size up will account for 1 mpg and if they weigh more that will account for the other 1 mpg loss.

 

i've messed around with it a little bit.. i think the sticker in the door jam says they should be 29 psi. i started out at 37 and now i'm down to 35. it does seem to ride a bit better but the mpg hasn't changed. i'm kind of noob with this whole thing as this is my first truck and first time switching out wheels and tires

 

Heavier=lower mileage
Bigger at same weight = heighten
Bigger means speedo is reading too low so you may in essence be driving faster = lower gas mileage.

 

so the new tires weight appx. 2 pounds more than factory but the wheels weight appx 2 pounds less than factory. should offset right?

 

Have you accounted for the % change. In your odo readings?

 

It Should. Also you are sitting a little higher which isnt helping the aerodynamics of the rolling brick.

 

The computer in these new ones tend to adjust for that.

 

no sir.. i thought i read on here that it would affect it odo by about 1 or 2 mph.. i could be wrong as i've read so many threads so i don't have to bug you guys..lol

 

i appreciate the responses, just wanted to make sure i wasn't over looking something. i tried to keep the weights as close as i could to factory since i do a lot of highway driving. i also should've stated that i went with the sl tires. i couldn't find a tire weight on goodyears website but found it on discount tire i believe..

 

How long have you had the new set on the truck?

 

lol, that's a funny question. i'm the one that started another post about general grabber tires. i originally went with the grabber atx but after two blowouts in less than a week, i had them taken off had the goodyears put on. i've had them on since saturday..

 

Ok.... give it a couple more weeks keep air pressure around 32 to 35 and see what happens.
Are you carrying anything in the bed during these trips or extra passengers?

 

no sir,, just me. i have about a 30 mile drive to work which mostly all interstate. since i've had the 2 blowouts, i've slowed way down due to the fear of having another at higher speeds.

 

Do you have a tonneau cover or shell on the truck... that may be the only way to recover the lost mpg.

 

i have a soft tonneau cover on it

 

Tread design will effect mileage as well.

 

Yes. Rolling mass equals total weight.

This is correct. You can find the tire size calculator to figure out the % change in circumference. This number is the error your speedo, odometer, and mpg are off by. Typically around 2% or 0.5 mpgs.

Oh really??? Do tell how a computer with no gps and no way to recalibrate ground travel can calculate anything different than the distance covered by one rotation of the wheel preprogrammed at the factory?

This is the silent killer. A deeper, more aggressive tread pattern creates more impact points in one revolution. The muscle to overcome that extra traction has to come from somewhere.