Why is my fuel mileage and power suffering with only 265/70-17's ???

[fullforce]

Long time thread reader here but never have posted much.
Search is usually all I need, but this time however I would like some opinons.

I have a 2005 V8 4x4 155,000 miles
Since the day I bought it about 2 years ago I have averaged around 17mpg around town and have even gotten almost 19mpg on highway trips.

I added a 2/1 lift about a year ago because the rake was just so terrible looking and didnt notice any fuel mileage change at that time witch I didnt really expect too, My tires still had tread on them so I ran them until they wore out.

So I have recently replaced my 265/65 17 street tires with a 265/70 17 General grabber AT2. I know this is a slightly heavier tire and about 1" taller, BUT.....

My fuel mileage will BARLEY hit over 15mpg highway even after I add in the slight odometer difference from the increased tire diameter. With AC on its below 15mpg

Also when my cruise is set it will downshift with the SLIGHTEST incline and it VERY VERY rarely would even unlock the converter in 5th gear before the tire swap.

I have owned many lifted truck with 35-38" tires before but I never would have expected this much of a drop in performance from a measly 1" of extra tire.
It literally feels like I have 35's on this thing now.

Maybe something else is wrong???
Has anyone else had this much of a change by only going to 265 70's??
Thanks

 

[truman3]

Maybe other things but compare the weights of both tires... Tread pattern will affect a little but weight is more of an issue wince you didn't go wider.

I went from stock Limited wheels with 265/60/18 Michelin to Fuel 17x9 with Nitto Trail Grappler and immediately lost 3-4 mpg. The tires were super heavy. I switched to TRD 17x7.5 wheels with Dynapro ATm 255/75/17 and think I gained back a solid 4 mpg! And that's a true 32 inch tire!


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[bamma]

Long time thread reader here but never have posted much.
Search is usually all I need, but this time however I would like some opinons.

I have a 2005 V8 4x4 155,000 miles
Since the day I bought it about 2 years ago I have averaged around 17mpg around town and have even gotten almost 19mpg on highway trips.

I added a 2/1 lift about a year ago because the rake was just so terrible looking and didnt notice any fuel mileage change at that time witch I didnt really expect too, My tires still had tread on them so I ran them until they wore out.

So I have recently replaced my 265/65 17 street tires with a 265/70 17 General grabber AT2. I know this is a slightly heavier tire and about 1" taller, BUT.....

My fuel mileage will BARLEY hit over 15mpg highway even after I add in the slight odometer difference from the increased tire diameter. With AC on its below 15mpg

Also when my cruise is set it will downshift with the SLIGHTEST incline and it VERY VERY rarely would even unlock the converter in 5th gear before the tire swap.

I have owned many lifted truck with 35-38" tires before but I never would have expected this much of a drop in performance from a measly 1" of extra tire.
It literally feels like I have 35's on this thing now.

Maybe something else is wrong???
Has anyone else had this much of a change by only going to 265 70's??
Thanks

Are your Grabbers 10 ply? Weight is a factor. You also need to add 3% to your calculations due to the increased wheel diameter. My 03 v8 with c rated grabbers nets me between 16 and 18 using hand calculations.

 

[wcjeep]

In addition to what has been mentioned. Tires have a wide variance from stated size and actual size. Be sure to verify numbers by hand and verify the speedometer.

 

[Atlanta_man]

Winter gas will be at the pumps soon, couple weeks really. Maybe that will help a little.

 

[07V8]

I typically saw 19MPG with 267/70 KOs @ 70 MPH. With the 275 E's I'm down to about 17 if consistently cruising on the highway. I can make that go as low as 13 depending on how I drive.

 

[bamma]

Winter gas will be at the pumps soon, couple weeks really. Maybe that will help a little.

Winter gas is worse for mileage.

 

[fullforce]

I did add in the roughly 3% for tire size difference witch was very minimal change in miles.

On the order sheet it says 4 Ply Rated is what I ordered.

I guess I should have just stayed with the 265/65
This is crazy for a big torque making v8 to loose this much power and mileage for a measly 1" taller (not even wider) tire.

Does anyone know where I can find a set of lower gears? I tow my boat some and I can only imagine how its going to be once I hook that thing up.

On a side note Im now getting code p0418 and p02445 for the secondary air injection not working

 

[Brian3676]

My 08 4Runner sucks with the bigger tires as well. I have 10 ply E Ko2 tires, im lucky to hit 15mpg.

 

[mpyle]

I did add in the roughly 3% for tire size difference witch was very minimal change in miles.

On the order sheet it says 4 Ply Rated is what I ordered.

I guess I should have just stayed with the 265/65
This is crazy for a big torque making v8 to loose this much power and mileage for a measly 1" taller (not even wider) tire.

Does anyone know where I can find a set of lower gears? I tow my boat some and I can only imagine how its going to be once I hook that thing up.

On a side note Im now getting code p0418 and p02445 for the secondary air injection not working

If you are having Secondary Air Injection pump failure this is your power problem not the tires. Others much more knowledgeable than I can chime in and explain the power loss but I think it acts much like shutting down cylinders.

edit:typo

 

[fullforce]

Its not in limp mode yet it actually just threw the code after I started this thread yesterday.
kinda ironic I suppose

 

[RonJR]

I truly doubt it's the lift and tires. I added a 2.5/1.5" Daystar lift early this summer, and then later went from 265/70/17 fairly non-aggressive all-season tires to 255/75/17 BFG KO2's. Zero impact on mileage for all of that. I still get 19.5mpg at 65mph on the interstate.

Coincidences do happen, and sometimes it can be quite confusing. You'll need to look at what else might have changed.

Just a note: Tire weight gets a lot of press, but doing the math will show that 1 lb of tire weight is like adding 1.5lbs in your cargo or seating area. So, if you swap tires and add 20 lbs per tire, it's like driving with an extra 4x20x1.5 = 120 lbs inside. Not completely unnoticeable, but hardly the kind of thing that will cost you 3-4mpg.

 

[fullforce]

Thanks for chiming in, I'm gonna look into the plugs and maybe even check the back pressure on the catalytic converters to make sure there not getting clogged (they do smell bad under load?)

 

[Bluesky 07]

[MENTION=134884]RonJR[/MENTION], your numbers are for a V8?

Also, no one mentioned rolling resistance. It's been years since I researched highway vs. AT tires but IIRC, that was a big factor in the performance hit. I had actually bought a set of ATs for my Xterra and it felt like I was driving across fly paper. Exchanged them for highway tires and never looked back. I've become a Michelin fan and run their highway tires exclusively on our vehicles. Tread life and all-weather handling more than balances out the extra cost, and they're more than adequate for the places I go off the pavement.

 

[RonJR]

Yes, for my 2006 Sport V8. This was on a recent trip from Loveland, Co, to Grand Junction, CO, then down to Ouray, and return. Averaged 19.5 over about 700 miles as measured at the pump.

It's all interstate, but since it's mountain driving speed limits are lower. Mileage drops quickly at 70 mph and up, down to about 17 at 75 mph.

My BFG's are C-rated, not E-rated. That might make some difference. Inflated to 40 psi.

 

[fullforce]

Not sure what the rolling resistance is on these generals but must be horrible, wish I could try a set of bfgs for a week just to compare.
I keep mine at 40psi also, maybe I should try higher

 

[jfry008]

Not sure what the rolling resistance is on these generals but must be horrible, wish I could try a set of bfgs for a week just to compare.
I keep mine at 40psi also, maybe I should try higher

Did you get the LT265s (load E rated) or the SL/P rated 265s?

Far right column is the weight. Load E tire is 12lbs heavier than the P rated and probably 15-20lbs heavier than your previous street tires.
Rolling resistance also probably took a dive, as previously noted.

 

[mpyle]

I truly doubt it's the lift and tires. I added a 2.5/1.5" Daystar lift early this summer, and then later went from 265/70/17 fairly non-aggressive all-season tires to 255/75/17 BFG KO2's. Zero impact on mileage for all of that. I still get 19.5mpg at 65mph on the interstate.

Coincidences do happen, and sometimes it can be quite confusing. You'll need to look at what else might have changed.

Just a note: Tire weight gets a lot of press, but doing the math will show that 1 lb of tire weight is like adding 1.5lbs in your cargo or seating area. So, if you swap tires and add 20 lbs per tire, it's like driving with an extra 4x20x1.5 = 120 lbs inside. Not completely unnoticeable, but hardly the kind of thing that will cost you 3-4mpg.

Sorry for veering off topic a bit here.... any pics of your runner with the 255 KO2's?

 

[RonJR]

Sorry for veering off topic a bit here.... any pics of your runner with the 255 KO2's?

Here you go.



I like the size. It's a full 32" diameter but the slightly narrower width makes it fit well with no rubbing and theoretically should be good on packed snow and ice.

 

[mpyle]

Here you go.

View attachment 221638

I like the size. It's a full 32" diameter but the slightly narrower width makes it fit well with no rubbing and theoretically should be good on packed snow and ice.

Looks good! Thanks

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