How much can little larger tires effect fuel economy. i went from the 235/80/17 stocks to the new bf goodrich 255 mud terrains. I have lost about 3 miles a gallon. Is it the tires or something else?

 

Have you recalibrated the odometer?

 

I went from 265 to 285, reset the Revs per Mile for the new size. I get better highway, worse local - basically no change in overall mileage. Before I reset the ecm, it was terrible shifting and overall performance.

 

I went from stockers to 35x12.50R18 and my MPG had the bottom fall out. I even have tinkered with my Smarty Jr. But I lost a good 5 MPG. The
lie-o-meter likes to tell me I get 19, but when I hand calc it's more like 13-14

 

I just went from 285/70/17 to the same 255/80/17 BFG KM2. The new tires are about 1.3" taller, but 4lbs lighter. If the tread were the same I would expect a increase in mileage, but since the tread is much more aggressive I am expecting no real noticeable change..

On your rig you have increased weight by 3lbs/tire, and gone from a hwy to a mud terrain tire, a slight decrease in mileage isn't abnormal. You also have to account for the 4.7% larger tire. So if you now get 15 mpg, its really 15.7.

 

Recalulated speedo with with my bullydog. I set it at 33" tires. i have lost about 2 MPG on the highway and around town close to 3.

 

I would say its the mud tires. They're an aggressive tire compared to a road tire. That it more than likely the reason for the lose.

 

You'll want to use a GPS to verify the speedo, 33" is a bit too tall for these tires. I am at 32.2" on mine, and its within 1%. BFG puts the rev/mile at 625, which means 32.3" for a new tire. Unfortunately that may drop your mileage even more...

That drop seems quite large for these tires.

 

When you play you will lose.

 

235's? I didn't know they put such a skinny tire on any of them. I thought 265 was stock? My 265's already look too skinny in a mud terrain, wish I held out for the 285's that were on backorder, I can't imagine 235's.

 

Must be a dully......265 is stock for SRW.

 

265 is the most common, thou some came with 245's, and dually's came with the 235/80's.

These 255's are skinney, but I really like the look of em.