Gas mileage is effected, negativly, as is pulling power. When I went from 265/70/16's to 285/75/16 on my Suburban my mileage dropped about 10%.

Bigger tires and lift kits can also cause the suspension to wear sooner. If its a new truck lifting over a certain amount can void the warrenty as well.

 

If you are buying a newer truck buy one with 17" rims that make it look bigger with the 4x4. This should be big enough to do what ever you need and it still rides good and pulls good. If you want a bigger truck buy a 250 psd that will pull good. the 150 is the best selling truck. i have had two of them a 97 2 wheel drive and i just bought a 2001 4x4 lariet i love the leather is is ever forgiving. no problems with either one

 

You risk wear and tear and a higher than normal center of gravity. For general work, they aren't that much use.

 

One reason we dont put large tires on trucks here is because of the snow. You would want the narrower tires for better traction. I doubt u have much snow down there, but wider tires sill also hydroplane easier.

 

I've got a 2001 Ford SuperCrew; 1998 Ford SuperCab and a 1999 Ford Expedition for my wife. ALL have been great. No problems to date. (Knock on wood.) Also, they have more head room in cab then any other brand I've tried. I'm 6'5" and hate banging my head on the roof every time I hit a bump. Don't do that with the Fords.

Mike

 

I have some BFG All Terrain's on my 99 F-150 2 wheel drive. I believe they are 295-70-R16's They fit just fine in the wheel well. It knocks my speedometer off by 6 mph. So when it says I am going 55 I am really going 61. My gas mileage went down about 5% and yes it rides comparatively rougher than with the stock tires. But hey, they look way better!

 

are you really getting worse milage or are you just registering less milage per gallon due to the larger tire size???

hmmm...

Derek

 

you are getting worse mileage. for example: i have 3.73 gears. that means for every 3 turns of the driveshaft, my axle turns .73 of a turn. but with bigger tires, it wont turn as much, therefore using more gas (more rotations of the driveshaft) to get where you want to go. Bigger tires also mean more "surface area contact" with the ground. So you will get BETTER traction with bigger tires as more rubber will be touching the pavement.

Although, the bigger the tire, the more stress can be put on the axle. therefore causing some components to go out faster, such as u-joints, and CV joints (all post '87 chevy's and / all f-150's).

If you are wanting bigger tires so your truck will look better, thats dumb. WHy spend money on something that isnt going to return a profit? Spend money on a new trailer, or better equipment.

But if you are going to run 35" tires, get 4.10 and better yet 4.56 gear ratios in your axles.

 

Let me explain differential ratios quick...

When someone says I have a 4.88 or a 4.10 it is the ratio of ring gear to pinion gear... meaning 4.88 to 1 or 4.10 to 1.

If you have a 3.73 in the rear end, your ring gear has 3.73 times more teeth than your input shaft pinion gear...

The larger your ring gear the more drive shaft rpms are needed to turn it the same # of times as w/ a smaller ring.

Larger tires will effectively lower your differential ratio. (Sort of)

BETTER mileage on the highway, but it will take more torque to get going from a stop.

 

Larger tires give you taller gears. The ratio is about one inch of tire for one tenth of gearing. So if you upgrade to about two inches taller tires and you started out with a 3.55:1 ratio at the axle-your new ratio is about 3.25:1.

On an F-150 I believe 3.73's are an option. This is a good ratio for light towing with an auto or heavy towing with a five speed manual. If you plan to tow and are unable to get lower gears I would stick with stock tires with the auto but upgrading with the manual shouldn't be a huge hassle(assuming the gears are close on the tranny)

As far as gas mileage---Taller but not wider tires (example:upgrading from a 245/75 to 245/85---about one inch taller) should improve your actual mileage but will register about the same by the odometer which will not read as many miles as you have actually gone.

 

BETTER mileage on the highway, but it will take more torque to get going from a stop.

Maybe in theory but not in practice. My Suburban with 285x75/16 got worse mileage city and hwy than with 265x70/16's, without towing

If you live where there are no hills and don't tow you'll get better mileage on the highway but not in the PWN.

And it's not just because the speedo is off, I recaliberated it so it was exactly on, both before and after, mileage dropped 10%.

 

You guys lost me a long time ago but what I originally wanted to know was whether or not it would be harmful to put tires on, say a Ford F-150,that are just a little bit larger than the original ones.I don't want a "monster truck" or anything close to it. Jim

 

It won't truly hurt your F-150. Things such as your CV joints and u- joints you may see wear out a little quicker, but no it won't hurt your truck, oh, and I put larger tires on my truck because I got the BFG All Terrain's por nada!