Since people are always asking about how much power/gas mileage they will lose if the got to a bigger tire, I thought I'd offer some observations.

My Truck:
1996 4Runner SR5 4x4
V6, Auto Trans
15" wheels, 3.90 gears

I live in the northeast... very little of my driving is done on flat ground. I live on the top of a good sized hill, so I am constantly going up and down.

My rig started out with 28" Firestone Wilderness ATs.

I replaced them with 32" Dueler ATs. I did notice a slight drop in power and gas mileage, but it wasn't a big deal... the power was only noticable when towing and accelerating up significant grades. The mpg loss was only about 1.5mpg. IMO, 32" ATs are fine for stock gearing.

I replaced the 32s with 33" Firestone Destination MTs. The loss in power and gas mileage is significant. I am constantly fighting to keep the truck at speed on even the slightest uphill grades. I've lost about 3-4mpg and the truck is a dog most of the time. IMO, 33" MTs are too much for stock gearing (at least for my 3.90s).

The thing I don't know is how much of it is due to the fact that my current tires are MTs vs the fact that they are 33s.

 

Since I think it's mostly just me and you Jackson that started out with 3.90's, I can add some thought into this thread.

As I said I started out with 3.90's and 28" bla bla blas. Then I switched to a 16" wheel with 265/75/16's AT's and noticed a big decrease in power and about a 1-2 mpg decrease.

Then I decided to regear to 4.88's to get better gas mileage (what was I thinking) and for more power. I did get more power, but gas mileage became worse, a lot worse. Also my highway rpm's are about 3k going 80 mph. Since our rigs redline at 6k I'd say that's a little too high. My next plan is to go to 33" MT's back down to a 15" wheel (might be steel though) and we'll see how that goes.

So here's my summary of my experience:

Gearing - 3.90s Tire - 28" Wheel - 15" Miles per tank - roughly 280
Gearing - 3.90s Tire - 32" Wheel - 16" Miles per tank - roughly 240
Gearing - 4.88s Tire - 32" Wheel - 16" Miles per tank - roughly 210

And these are all summer mileages. So Winter you can drop about 20 miles.

edit: I have no roof rack, or steel bumpers (yet) so really no extra weight except sliders. And I live in hilly areas as well.

 

How would I determine my runner's gearing?

 

RB's Site

 

I am in the same boat. I have 3.90's.

When I purchased the truck, it had 70xxxx miles on it. I recall mileage back then repeatedly being up near 300 miles a tank before the gas light came on. Sometimes upwards of 320. This was also with no mods whatsoever.

I then kept the stock wheels, and purchased 265-75-16 BFG-AT's. The extra size did not really adversly affect the mileage much. I can guess maybe 1 mpg. Not really much. Still near 300 a tank.

I did around that time start putting lots of mods on the truck. The TJM-15 and at that time a yakima roof rack with q-towers up forward and the lift. This knocked the mileage down another 1-2 mpg. The real mpg killer on my rig was the safari rack the barn door of aerodynamics. I now get at best 220 a tank. I can't see myself getting 285's and dropping the mileage any more. If I could regear with stock toyota gears 4.33's or 4.56's and see the same mileage with 285's (near 220 a tank) I would do 285's.

 

Thanks!

 

I have had 275/70/16's, 265/75's, and 285/75's. I've had then stock and blown.

275/70-16's at about 80 when i got it would get me about 16.5 MPG's

275/70-16's at about 80 after new fuel filter, air filter, spark plugs, MAF cleaning, TB cleaning would get me about 18 MPG's

265/75-16 Nittos got me the same - 18 MPG.

265/75-16 Bridgestone Dueler MT's got me about 17 MPG's

285/75-16 Goodyear MT/R's @ 80 MPH would get me about 15.5 to 16 MPG's

285/75-16 Goodyear MT/R's @ 80 w/ a SC would get me about 16.5 MPG's

same as above w/ new O2 Sensor got me about 17.5 MPG.

same as above but at 75 MPH gets me about 18.5 MPG and at 72 MPH, I got 19.9 MPG.

that's all w/ no roof rack, and the only extra weight is negotiable since the winch and SC might only add 100# total. those numbers are w/ a load in the back consisting of probally 75-100# of luggage along w/ at least one passenger and are for a full tank for at least a 200-mile trip w/o stops in slight to moderate hills.

 

I agree, with my 33 MT's and 4.10 gearing, climbs up long mountain passes are a bit of a chore. Its about the only reason I'd consider going to a supercharger. Depending on what your preference is (assuming you want to stick with the bigger meats), it comes down to going to a supercharger for better on-road performance, or regearing and throwing a locker in the front diff while you're at for increased offroad performance.

EDIT: since you're currently open front and rear, re-gearing would be a good excuse to throw a locker in the rear as well...

 

No problem. There are some links on that page that might help as much as the page itself.

 

Bought mine used, so I don't know what it did stock. I'm different from most b/c I have a 5spd '99 4x4 V6. I started with 3.90's, but quickly went to 4.30's from a Toyota salvage yard. With 4.30's and 32's I got about 190-200 miles per tank, now with 33's and 4.30's I get about 170 miles per tank. This is filling up at about 1/8 tank left before the light comes on. Also this reflects me driving about 70-80 mph on the interstate with a roofrack and a 33" spare on the roof. I'm about to go with 4.88's, so we'll see what that does. I have never replaced my O2 sensor, but I have replaced the maf and it made no difference.

 

Wow Brett that is some crappy gas mileage. And I thought that mine was bad.
Do you think that all the stuff you have added like the ARB bumper, winch, sliders, skids, etc., has added a lot of weight? Or is that negligible since you had to remove factory components (weight) to add that stuff?

With my A/T, 4.10s, and 32's I am getting around 275 per tank. Less if I am on the interstate. I am always right around 150 miles at half a tank, after that it depends some.

I am curious to see how your 4.88s will change things.

 

Crap, I forgot to correct those, so you can add 10% to each number, but yes it still sucks. Good thing I only drive it about 10k miles a year! I am definitely heavier than stock-5 285 tires probably weigh about 125 lbs more than the stockers, skidplates are way heavier than stock, sliders way heavier than running boards, front bumper and winch adds about 125 pounds over stock, rear bumper is a little heavier than the stocker w/tow hitch, roofrack is heavier, cargobox and all it's contents way heavier-I would bet I'm close to 500 lbs heavier than stock.

 

I really think the MT's vs AT's have a large play in the factors here too. That and the roof racks. Since I drive my truck 25k a year. I'm for sure not ever getting MT's for the few times I would actually need them.

 

I thought about the fact that you don't drive too many miles a year in your 4Runner. Good thing for work trucks huh? I am only averaging 12K per year so far for the first 5 years. So I'm happy about that.

 

On my trip to Houston this weekend I got roughly 15 mpg @ 85 mph and 20.5mpg @ 72 mph.
I had no idea that 13 mph would make such a huge difference in MPG!

 

is there an equation for computing the % change in the speedo and odometer when larger tires/gears are added/changed

 

never mind. MY BAD

 

Hey, found that bottle of filter oil rolling around in the floor of my work truck-you still want it?




Sorry, thread hijack over.

 

***hijack on***
Sure. Give me a call and I will meet you somewhere!
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ok

end hijacking