I was thinking about getting some 285 or 305 tires on my 2006 F-250 5.4L. I was wondering how much power and fuel milege I will loose?

 

To be honest, I don't think that it will any noticable difference. What gears do you have in you truck... 3.73 or 4.10?

 

Wider tires have more rolling resistance, so it will affect mileage a bit.

 

When I purchased a 2nd set of tires for my 06' F-350,,originals being the 18' contis,,I wanted a more aggresive tread for my 2nd set,,,I found a set of 17" Alloys takeoffs from and 07' F-250 (new) and purchased a set of Hankook Dyna-Pro RT03 MT 285/75/R17 load range D,,they are 33" tires, same height as the 18" Contis, I do notice a bit more rolling resistance from the Hankooks,,,not sure if it is from the LR D's at 65 psi, compared to the Contis LR E's at 80 psi,,,but it does roll easier with the Contis,,,but the difference in traction is amazing,,,and the Hankooks seem to be wearing OK too,,,only have them on for winter as I had them studded also.

 

when I had my 06, It came with lt275/70R17. I put 295/70R17 on it and change the tread from BFG to cooper discovery Stt. I lost about 2 mile per gallon.

I had the 5.4 with 3.73 gears.

 

The OP didn't say anything about changing tread patterns (ie: going to a M/S tire). If the only change is the size from a LT285/65R18 to a LT305/65R18, then it's only about a 1/2" difference in section width. I agree that will make a difference. The change is also a 1" difference in diameter. The combination of increased section width and diameter will have a greater impact if he has 3.73 gears as opposed to 4.10 gears.

Here are the specs for the BFG All-Terrain A/T KO's.

<TABLE class=specs id=specs-wide cellSpacing=0><TBODY><TR><TD>LT285/65R18/E</TD><TD>125R</TD><TD>RWL</TD><TD>67553</TD><TD>8 - 10</TD><TD>11.5 on 8.5</TD><TD>32.7</TD><TD>16</TD><TD>636</TD><TD>3640@80</TD><TD></TD></TR><TR><TD>LT305/65R18/E</TD><TD>124R</TD><TD>RWL</TD><TD>35237</TD><TD>8.5 - 11</TD><TD>12.2 on 9</TD><TD>33.7</TD><TD>16</TD><TD>617</TD><TD>3525@65</TD></TR></TBODY></TABLE>

 

I have the Goodyear Wrangler Pro-Grade Silent Armors on it right now in a 265/75/17. I was thinking about just going to a 285.

I have the 3.73 gears. I dont want to loose much power or fuel milege. I dont know how much of a difference I would notice.

 

How tall are the tires at which you're looking as replacements?

 

I went from a 275/70R18 to a 325/65R18 on my 2008 and lost about 0.5-1mpg. The tires are the exact same height but the 325 is 13'' wide vs. 11'' for the 275.

 

I went from 275/70-18 stock Continentals to 285/65-18 BFG tires. Both are load range E tires. The two tires are just about the same diameter with the BFGs being just a bit wider.

Fuel mileage has not changed at all. Still see an average of 15 MPG in mixed driving. As others have mentioned, the difference in traction is amazing.

Lou Braun

 

The math don't work for the tire height.
275/70R/18 = 33.15" tall 10.8" wide
325/65R/18 = 34.63" tall 12.8" wide

Thats about an inch and a half height difference. If the 325's were 60 series then they would only have a quarter inch difference.
I'm not trying to bust anybodies chops I'm just saying the math don't lie.

Tim

 

BFG's AT KO tire specs:
- 325/65/18 -

Tread width: 9.7"
overall height: 34.7"
Load: 3195 lbs.
max press: 50 psi.
Load Range: D
weight: 67 lbs.
revs per mile: 599
section width:13"

I was considering these tires but I don't have the recommended
9.5" rim and am leaning more to a highway tread design.

 

Your 100% correct. If I had read my own signature I would've realized I made a mistake. My tires are indeed 60 series just like my signature states.