So I've got a 1996 f150 with the 4.9L and a 5 speed in it. basically.. I get ****ty mileage regardless of how i drive or what I'm towing.. 10-13 mpg whether I'm in town driving errands, towing a 4000lb construction trailer, my boat, or empty. I get about 15 driving 70-75mph when I drive from Seattle to Portland (180 miles), but the RPM's are waaayyy up there..
I'm not looking for ways to improve mileage... it's a truck, I've had it for years, always reliable and I'm not planning on selling it any time soon... but, it's in need of new tires.. and I figure, if I'm gonna replace the tires, I'd much rather have a bigger All terrain tire.. which would put the RPM's down from 2300-2400 to about 1900-2000 when driving 70-75 IIRC from a formula I found a while back... which is about 75% of my driving going to school and coming home (Seattle to Portland) and given my mileage doesn't seem to change towing a trailer, vs. heavy load, vs. empty, seems like it shouldn't drop my mileage significantly..
the long term plan is to swap out a 4wd front end and tranny when this tranny/clutch goes, or I find a good cheap donor truck.. but right now, it has a 2.5" suspension lift that basically puts it about the same height/stance as a stock 4x4.. almost levelled.

It has the stock tires and wheels right now, 235x75r15.. If I wanted to go to something like a BFG all terrain T/A KO.. would 33's fit first of all on the truck... and secondly on the stock aluminum wheels, and what width?

If I have to buy a different set of wheels.. that opens my options up right? if I went with a 16" wheel, there are a lot more sizes of tires available.. not necessarily a BFG, but other brands of all/terrain tires..?


So basically looking for a bit of advice on where to head with this.... thanks

 

Well to give you an idea of what 33's look like here are 33" Wrangler Duratracs on my 92 4X4 with 4 inches of suspension lift. The tires rub the radius arms with ease at full lock.



Those are the stock 15x7.5 rims as well. Those tires are 33x12.5R15. I dont think they would clear very well with a 2.5 inch level on a 2wd. With the 15 inch rims there really isn't much to choose from. If you get 16's that opens up the possibilities a lot. Your tires right now are 28.8 inches. I would recommend for your truck to go up to 31's at the most. You can get the BFGoodrich T/A KO in 31x10.5r15 and it would work pretty well on your truck. Would just need a PSOM recalibration. I honestly would have gone with narrower tires if I could, but the wranglers were only available in the size I got for 15 inch rims when I got them. Now they ave them 31x10.5R15 as well if you like the tread pattern on them. More "beef" to them than the BFG's.

***Do you live in Seattle or Portland?

 

33's will fit on your truck.

Truck in my sig has a 3 inch body lift with 33's on it, had to space out the front bumper for them to fit, and they rub on the radius arms at full lock.

But I'm currently converting mine to 4x4 and I just bought some 15x10 wheels with 4 inches of Backspacing, to eliminate rubbing and tire shaking issues on the highway.

From what I have found on mine, 7.5" wide rims are way too narrow for a 12.5" wide tire.

 

they might rub at full lock with the stock rims. if you can find some rims with a little more offset they wont rub. i had 32's on my truck stock and it never rubbed, granted they were mounted on aftermarket rims with a good amount of off set. what rear end ratio are you running? stock size tires to 33s is going to really hurt your towing power.

 

Sounds like your truck needs a little tlc. My 4x4 F150 with the 4.9, auto and 33s got 16.5 mpg. I fit 33s on that thing in 100% stock form, even with saggy front springs with zero rubbing

 

Yeah, I would look into doing a tune up, not looking into bigger tires...My 351w gets better gas mileage than that after I did a tune up. You should be getting 15 EASY, and I know of plenty that get closer to 20.

As for the bigger tires, 33x12.5 does apparently work on those rims, but I would get a set of 15x10" rims. Big tires with narrow rims makes the truck kind of mush in the tires side to side. And if you ever have to air them down (or they just get low on air) it can unseat the bead easier. Also, most law requires that you have fender flares to cover wide tires, just a heads up to check the "rules" in your area.

 

What rear gears do you have?

I'd recommend no bigger than 32 11.50, but would say to go.with 31 10.50.

I'm surprised no one really said much on this, but larger tires and gas mileage don't belong in the same sentence, unless the word decrease is in the sentence too. The same is true of larger tires and performance.

 

I've done the tune up and all that stuff. when I bought it back when I was in highschool I took it to the dealership and did a full tuneup and fluid flush, and got consistently 10.5mpg after that, since then I've done all my own work on it, including that full tune up listed on the forum, distributor, wires, plugs, air filter, etc. I run castrol gtx 10w30 in it.. if anything, my mileage improved after my exhaust pipe started leakin a bit...

I've taken it on a 400 mile all highway trip, filling up, turning onto the highway, stopping once, and turning off, the cruise control set at 58 and got 21 mpg, so I know it is "possible" but when the speed limit is 70 and the traffic is goin 80 on a two lane highway it's not realistic or safe in my opinion..

I've read just about every "how to improve my mileage" thread on here, and i've done the things that people say helps on there but the reality is, other than driving from seattle to portland and back, all of my driving is stop and go short trips to the store, towin my boat, or when I was in highschool, starting cold, full heat, driving a mile and a half and shuttin it off, then same drivin home, sometimes with a full load of gravel, tools, or lumber in it.

sorry, I realize that was a bit of a rant, but I take pretty dang good care of my truck, especially for a 20 year old guy.. and my mileage has improved since doing my own work on it vs. the dealership sooo I'm doin something right.. but seems like we're livin in two different types of cities... I'm in a hilly area, with stop signs on every block, and it seems for every one guy that says they get 15mpg in the city, there's two sayin the 300 is a gas guzzler, and the V8's do get just as good a mileage..

I appreciate how quick you guys all responded with the general consensus seemin like 33x12.5 is possible on stock wheels but either a narrower 31 or 32 is probably the smarter choice unless gettin aftermarket wheels w/ different offset.. in which case I think I'd get a 16 inch, just to open up the options a little bit, but I was noticing, for example a 285/75r16 which is essentially a 33" tire, is $209 for a bfg a/t ko whereas a 33x12.5r15 is $176, and this trend seems to follow for most tires... why are they so differently priced for basically the same tire?

33x12.5 just seemed like a pretty standard size for people lookin to do a little off roading and not destroy the stock 3.55 axle(which is in my truck) and my friends have all had good luck with 33" bfg a/t ko's...

As far as 33's killing towing power.. I'd think that given that it's a manual, I'd just be keeping it in a lower gear when towing..? is that incorrect? other than the occasional dump run or yard of topsoil, my boats the only thing I see myself towing in the near future since I'm in college and not working construction anymore... and it shouldn't have any trouble towing that.

 

Do you live in Portland or Seattle? I'm guessing since you say it hilly where you live, its Seattle. I only ask because I live in Portland and Recommend Courtesy Ford for tires. That's where I got my set 3 months ago and it was $645 with alignment out the door. And that's the 33" Goodyears. I'm guessing for 31" BFG's you can get them for under $600 with alignment.

 

I live in Seattle, go to the University of Portland. I was planning on getting my tires in Portland though to avoid the sales tax so I will definitely look into them, thanks

 

Well, the point may be moot... I just picked up a running 1992 f150 4x4 to do the swap for $200, and it's got some 33's on it that are pretty worn down sooo I'll have atleast a baseline for fit and comparison before I buy a new set.