Stock Tire Sizes opinions?

[colstripguy]

I drove my first 6.7 today. It was a crew cab F250 Lariat.Very impressive, compared to my '97 7.3. I probably will order a Supercab XLT 4x4, probably 3.55 gears. What are members opinions on tire sizes? On the Ford build it website the 17" are the cheapest.The 18's looked good on the crew cab. Looking at Toyo's website, the diameter difference between 17's and 18's is an inch.I'm more of a function over looks type of guy. What opinions have you got? Thanks, Pete

[67powerstroke]

Depends what you are going to use your truck for. Are you a heavy hauler? Then go for 3.55 gears. If you drive mostly unloaded then I would get 3.31 gears. As far as function goes if MPG is your goal. The less rotatin weight the better. So get the smaller wheels... Good luck with you decision.... There are so many options...

[Nthorseman]

I haul a gooseneck combo horse trailer. Truck height is a big concern, smaller tires lower the truck and put more power on the ground for less fuel economy. The 3.55s will mean less fuel economy as well.

[colstripguy]

My dealer has 2 long box crew cabs, one with 17's, one with 18's. The 18's fill the wheelwell more, look better IMHO. But I measured the bed rail height, the pickup with 17's was about 57" high, the p/u with the 18's was 58" high. My '97 Supercab sits just over 55"at the bedrail. Also checked tire diameters at Michelin, Goodrich, and Toyo, and worked out the tire circumferences. The 17's average about 99.25" circumference, the 18's averaged about 104.3". That's about 5.5% difference in tire circumference,close to the 7% difference between 3.31/3.55 gear ratios. So.. 3.31 gears with 17" tires should behave like 3.55 gears with 18" tires? Plus give more clearance between my box, and gooseneck? Anybody see holes in this logic???? Thanks, Pete

[67powerstroke]

Sounds like you know what you're doing. I'm sure you will make the right decision. I bet you're going to get 3.55 w/18" rim. I like the wheel well filled up as well. I have 17" rim and planning 18"-20" with 33"-35" tires. Hope that's ok with my 3.31 gears.

[Supershooter]

Fuel Economy is a function of rolling resistence of tire, tire size, rear end gear ratio, final transmission gear ratio. All of those factors need to match how the motor functions. The power curve and the torque curve need to be maximized closest to the point where you plan to operate the truck for the majority of its working life. Each tire has its own rolling resistence number. Taller tires are more fuel effeicent, they have the least amount of rubber on the road. There are many factors that affect MPG. The truck I purchased, I ordered with 18's and 3.31, it'll be driven 45,000 miles a year mostly empty. Good Luck Supershooter