I have a 2001 F150 Supercrew 4x4 with 5.4L automatic and the standard 16" wheels/tires (255/70/16). In the Ford literature relating to my truck, it says the towing capacity in my current configuration is 7700 #, but if the truck has the optional 17" wheels, the towing capacity drops to 7000 #.

Why? Does Ford make other changes to the truck if you select the optional 17: wheels?

I'm thinking of changing my wheels to 18" Lightning wheels with 285/55/18 wheels. The diameter of this 18" wheel configuration is almost equal (off by 0.2 inches) to the standard 16" wheels/tires on the truck now. If I make this change to 18" wheels/tires, can I still tow the rated 7700 #?

Any comments appreciated,

Steve S.
Spokane, WA

 

It's all about tire height. When you have the factory 17" wheels, you will have a 265/70/17 tire, which is about 31" tall. A 16" wheel with a 255/70/16 is about 30" tall, so with the gear ratio being the same in both cases of say, 3.55, the taller tire will make that ratio a smaller number (harder to turn), like 3.38. The shorter tire just makes it "easier" to turn.

So your 285/55/18 tire will be about 30" tall. The same as the stock 16" setup. The only thing you will have to watch is the load rating for the tire itself. My guess is that it's not gonna be a "LT" type tire which would have load ratings of "C", "D" or "E".

You'll be limited only by the rating of the tire, which is probably gonna be "Standard", or "P" which is not as much as above.

 

Plus, keep in mind that 17" wheels already have a limited selection of all-terrain tires. I'd hate to see which ones are available for the 18" and the price they carry.

-Flea

 

Smaller diameter tires give higher engine rpms for a given vehicle speed; in effect, like Mitch says, giving you a higher number (lower ratio) rear end. And its the loaded tire height that counts--what is measured as tired height without load (off the truck) may not be the same when it is loaded.

Mitch is also right about load ratings--I would think that the 18" would not be rated as high as either the 16" or the 17".

Other than that, tow away!

 

Dont' forget. Brakes are less effective with larger diameter tires too.

 

Because the extra diamater changes your rear end geaar ratio. Not only the 17 inch Wheel and its tires but taller 16 inch tires from the stock will do this as well. An inch and a half taller tire will reduce your gear ratio by .25 or so. And they use the same rear end on all of them without any compensation for the different wheels or taller than stock tires.

 

Imagine you're on a 21 speed bike resting on a slight incline.
Ok, now imagine taking off in first gear. easy right?
Ok, now imagine taking off in 21st gear. Well?
(ok, no problem for you cause you're a tough guy)

Ok, now imagine you've got to haul the Butt sisters up the hill.
Bertha is behind you, her trunklike arms around your waist.
Bathsheeba is on the handlebars.
You can't see where you're going.
That don't matter cause you ain't going nowhere.

(I got all of this out of the owners manual under, specifications)

 

Here's another angle. My Expy has a higher rating with the 17" wheels. Don't forget about stability. If you have a taller tire, larger sidewall, you could end up with more sway etc. In the Expy's case, in 2000 with the 17" tire it went to a smaller diameter tire thus more wheel and less tire. Rating? 7800# and I think with the 16" was around 7000#.

Power and gearing are a big part of towing, but the bigger part is control and stability.