I live on a pretty rough road, so I upgraded to some BFG K/O E-Rated 265/70/17 tires, which are heavy bas****s. I'm now I'm seeing a loss of 3-4 MPG and would like to regain a bit of that if possible. If I re-gear, do I need to do both axles and is 4.56 the magic number or is this overkill? I read that there is only an increase in MPG around town but not on the highway?!

I was looking at these: Nitro Gear 4.56 Ring & Pinions for 2010+ FJ Cruiser, 4runner, Prado 150 Rear - New Products - Nitro Gear & Axle

I can't imagine that size needing 4.56's. Those are usually for running 35's. Even with 33's stock gears are fine, although some people go with 4.10's. You'll have to do both the front and rear and yes, your city MPG may improve but your highway MPG will be worse. The overall cost of everything pretty much negates and gas money you'll save.

I believe 4.56s are the only gears available for us at the moment. But for a 265 all terrain I can't imagine needing to regear. I have 33" MTs and while I notice their weight, its hardly needed to regear for. It's just a want. Harper7 is the only one that I know of that has done this so far. Maybe he will chime in here.

You have to do front and rear to match.

5ths have the new bigger stronger 8.2 rear diffs and the 4:56's are the only ones out at the moment.Better to have East Coast Gear build them for you and swap them out with a core charge and send yours back after the swap.

I get maybe a little better gas mileage around town but nothing to write home about. Lose a little mpg at highway speeds as at 70mph I'm taching almost 2400rpm and that's with 34" tires.You would be taching even higher with 33's. Didn't buy them for the gas mileage ,bought them to improve the low end torque and driveability running big tires. 4:56's and ARB lockers

I second what Harper said. His Runner is a machine that is specifically built to be AWESOME. I approve, and I know Barney Stinson would approve as well.

For those of us who, like myself, love having the capability of a Runner but unlike Harper rarely put it through anything off road that will make it break a sweat, 4.56's are going to be a bit aggressive.

I too am interested in getting a few more RPM's spinning to improve overall power. I'm under no illusions that gears will improve my gas mileage to any financially reasonable degree.

I would be the first one in line if a quality company released 4.10 gears. If you do the math, 33" tires with 4.10 gears on a Runner should give you a gear ratio that is just a couple percent lower than the stock gear ratio.

From where I sit, these few extra RPM's would be a welcome addition. The Runner would be a just a little bit closer to the torque curve to compensate for the heavier / larger tires so many of us run.

best bet, send those tires to me and get lighter tires

Are you sure that the drop in mileage isn't because of the lower temperatures outside?
The lower the temperature = the worse mileage you will get.

You do not need 4.56 gears for a tire less then 32", even with the added weight. You would probably lose more mileage. You may want to look at lighter wheels and/or braking components.

Koz

What pressure are you running? You should be at approx 55 psi.

Koz

4.56 gears aren't really necessary until you get into the 34"-35" tire range. We are running 35" Falken Wildcats and with 4.56 gears we are averaging about 14mpg in town driving.

Thanks for all of the responses. Part of the reason is probably the pressure and perhaps my heavy footed driving. I've got them at about 42 psi since 55 psi rattles me to death.

At 42 psi you will get lower mileage!

Koz

IIRC the recommended PSI for the 4runner is 32. I wouldn't go over 38 at all. Tire psi is vehicle specific, not totally tire specific. If you really want the best psi do the chalk test.

I agree. The 4Runner stock tire on the Limited has a load index of 107, meaning it's load capacity is 2149 lbs (ON A CAR). Since it's been installed on a "truck" it's load capacity is reduced by .91. So .91x2149=1955 lbs.

Now checking the load carrying capacity of an LT265/70R17 at 35psi we see 1890 lbs and at 40 psi we see 2075 lbs. So each PSI over 35 psi adds 37 lbs of load carrying ability. (2075-1890)/5=37.

So 35psi+1psi+1psi OR 1890+37+37= 1964 lbs which is greater than the load carrying capacity of the OE Tire on the Limited 4Runner. Since the Limited 4Runners are a few pounds heavier than an SR5 or Trail, you really have nothing to worry about running these at 37psi.


You can run a 285/70R17 even lower than that safely because it has a greater load carrying capacity than the 265 at the same psi's.

Confused?

Recommended PSI is for passenger rated tires not LT or light truck rated tires. PSI on a P rated tire is less to achieve given weight objective LT is much higher.