The stock 265/75/16 tires need to be replaced and I was considering swapping 285's on the stock wheels. Will I notice an increase in fuel consumption? I realize that calculating mpg will need to be adjusted due to larger tires since the speedometer will be slightly off.

 

The error will be only 3.7%. At 2000 RPM, you will be going approximately 72.6 mph in fifth gear. Conversely, at 70 mph, you will only be turning about 1925 RPM instead of 2000 RPM.

This is not too bad. You may see some slight decrease in mileage. Biggest issue will be if you tow a large aerodynamic drag (like a travel trailer). May be hard to get in the "prime" zone of 2000 RPM.

My experience is that speedo already reads high by about 3%. So...yours may actually now read correct speed for a given RPM.

 

On reconsideration, tire diameter may actually not be the problem for you. You may want to consider if 285s can be put on the 7" rim width or not. Reading tire charts would indicate this is not recommended. The Michelin chart says the rim width for 285 is 7.5 - 9.0".

 

You may loose a couple MPG. Also the tire is heavier so ride will suffer some. Also I have found wider tires tend to have problems with accelerated center of the tread wear. The center tends to bulge more so if you want to get all your tread life you have to lower your pressure which is going to further damage MPG. I am not a fan of Monkeying with tires unless the vehicle is pure toy which means it does not matter if you screw something up because it is just a toy. Changing tire sizes can also lead to bearing and suspension problems. My old F350 had 285's on it and I hated them. They were expensive and did not wear worth crap and they were noisy to boot and hard to keep balanced. I sold it before it needed tires. Can you get the load range you want in a 285?

Perry

 

Ya you will see a bit more fuel use.
They will fit on stock rims fine. If you can't get your shop to mount them then you need to find another, but there should be no issues. Many have mounted 295's and wider on stock rims.
My 285's are lighter than my winter 265 set. You should be fine in a D rating if you watch the weight rating on them or go the E's. D rated will be lighter, but also have a little more flex on sidewalls. I have two seasons out of mine with no issues.

 

I don't see the tire weight affecting anything, actually I don't see any of the problems above happening with that small change, and OP you might even gain a little MPG if you just do long flat commuting. A larger tire will give a softer ride also if the rating is the same etc.

 

I'd be swapping out a stock size BF Goodrich Long Trail for the BF Goodrich All Terrain A/T. I need E rated tires for towing. Rim width for that tire in a 285/75 is listed at 7.5"-9"

 

im new to diesels but the perks of a diesel engine is that it has the tq to haul more than a comparable gas engine but it will also see less of a mileage decrease as well. With that said i dont think you will see any 'significant' change in mpg from going to a 285 to a 265. On my old gasser i went from 265/70/18 to 325/60/18 and only saw a loss of 1-2 mpg. I would like to know what mpg people with diesels excursion are seeing in terms of mileage with this bigger size. Hope this helps.

 

285s on stock rims are no problem, that is what the vehicle was designed for and what the computer was calibrated to as well.
Mine with the 7.3 has had no issues getting 20mpg hwy with 5 people in it, no impact whatsoever on such a small size change.

 

I am running BFG AT T/A LT 285 75 16 "E"`s on the stock rims with no issues, not even any tire wear problems. my fue mileage has not decreased that I am aware of. maybe at most it may drop .3mpg, maybe!

I think the big factor is going to whether or not you have 3.73 or 4.30 gears. I have the 4.30`s. I don`t think I would want the 285`s with the 3.73`s. never mind I see that you have the diesel, won`t even be an issue.

 

They'll fit on the stock rims, be prepared that a Discount Tire or similar store might give you a lecture on the rim size, no worries however. I've done it with two diesel Excursions, one a 2000, and the present '02 . Both 4x4 Limiteds.
Instead of conjecture, I'll give you some hard numbers. Keep in mind these are for 7.3PSD, not 6.0, but are calculated mileage from about 130,000+ miles of combined city, highway, and towing with comparison between the two sizes.
My 2000 Excursion lost 1.7 across the board going to 285's, my '02 an even 2.0mpg. These are hard numbers going from stock Firestone 265's to BFG AT KO 'E's.
I'm not convinced there is any more wear on the truck due to increased size. Fact- the tires ARE heavier, rolling resistance is higher even given you're running higher PSI, they ride rougher, and they don't last as long. The BFG's have a long history of balancing issues; this is nothing new and you can live with it.
They look a helluva lot better, and that's good enough for me.
Jim

 

someone already beat me to it.

285's, are the actual designed-for size, and will work just dandy,
at least on pavement.

If you want to see a small write up with pics a few years back, click my homepage link.

john
www.roenation.com

 

I went from 265 to 286/75R16 Michelin M/S2 tires. Got them @ Discount Tire Co. Small decrease in indicated milage. However, tire size changes both indicagted speed & milage. My 03 6.0PSD indicates a slight drop in milage, but with tire size factored in, the milage comes out about the same.
By the way, ride is MUCH better with this tire. Went from 265 Michlin M/S to 285 Michlin M/S2 E rated. I run lower air pressure (50 to 55). Michlin will actually give you advice on tire pressure. I am VERY happy with this change, and wouldn't go back.

 

You're website is great! What type of mpg loss did you experience going from 265, to 285, and then finally to 315's?

 

Ive been rocking the 315's on my stock rims and never had a problem for them fitting so Im pretty sure a 285 would be a cake walk.

As far as fuel wise, If it did drop I didnt notice that it did. Might be 10-20 miles I lost.