Tire size and MPG

I'm sorry if this has already been discussed. I searched around the forum and didn't find anything. I've decided to start putting a little money into my truck and will finally be getting a 3 inch lift next month. At first I didn't mind sticking with the 260 70 16's that are on her. Then I started thinking about how it would look and want to do 285 75 16's. Does anyone know how much of a drop in MPG I can expect?

 

I have read that it is about 2mpg less. Key word "read", I have not gone to 285s yet

 

260 70 16??? do you mean 265

 

yeah, sorry. 265's

 

when i went from 265 to 285 i did see a drop but tought to tell how much. Keep in mind there is a lot of weight that is added on, and you are having to spin that. Plus another thing to keep in mind is the change in diameter of the tire. If you increase that you will have a different reading, so it may not just be the added weight but the change too.

 

in respect to the reading...i'm assuming that there might be a difference in speedometer read out?

 

theres a speed to speedo difference from the factory, people get closer to the correct read outs after they add 285's (not everyone has the same deviation).

ya more weight to the truck and also more rotational mass at the wheels. you got a v6 so no need for regear

 

The gearing will change with a 265/70/R16 to a 285/75/R16. My truck has 4.10 ratio gears and going to 285s will make the engine turn a little lower RPM. This would tend to increase the gas mileage as long as you stay in the green range on this chart http://www.4lo.com/calc/geartable.htm. But with the weight and larger footprint of the tread the gas mileage decreases.

I currently have 265/70/R16 on a V6 04 Taco with 4X4 with 4.10 gears. I expect a 2 mpg drop in MPG going to 285/75/R16. That with the rubbing is making me think a 265/75/R16 may be a better tire for me. The gear ratio will change to lower the RPMs and the weight will not be as big with 265/75/R16. But tires are so expensive I hate the thought of wising I had gone as big as I can. I got the info on the MPG drop from reading about people complain about the MPG drop from 285s (33s). I hate compromises but going to a big tire has negative effects. A 265/75/R16 will still fill the wheel well and the milage should be a little better that a 285/75/R16. I would guess 1 MPG.

 

Going from a 31 dia to a 33 dia speedo reading changes 4 mph. You think you are driving 60 and you are driving 64 ( watch out for the PO PO ). Here is a calculator link http://www.4lo.com/calc/gearspeedo.htm

 

Try and get a passenger rated 285, they are usually 5lbs less per tire.. is what i will try and do if I can ever wear out my stock 265s. Nittro makes one I know of...Firestone and Duellers come in P rated 285s..sound help save some $$

 

I had a negative experience with passenger 2 ply tires that were Poser Offroad Tires. I was 30 miles from anyone that could help me in West Texas and I got two flats from rocks puncturing the tread on one and on the other tire puncturing the side wall. I put the spare on the ground on the side wall puncture and left the tread puncture on the ground. Lucky for me I had goobs of Goop in the tires. And it held long enough to get to a temporary repair shop.

I dont buy truck tires that are less than 6 ply now. But I like to go off road

 

Dang 2 ply tires, do they even exist in 285? But your right, how bad are you going to be beating on them. If you are in to the sharp stone trails off road climbs..etc go with the LT rate tires. I'm leaning towards the Duratracks after some data comes in, with the Coopers and Nittos a close second.

 

I have been looking at the Duratracks also but need reviews, Except for the name Firestone the Firestone Destination M/T looks good. I like the reviews,wear, wet traction

 

You guys are awesome! Thanks for all the input. I think i know about what to expect on the mileage now. Kinda silly to be worried about MPG driving a 4WD. Next problem is to pick out what brand I want to go with. Thanks again!

 

I dropped about 1mpg going from stock 265/70R16 to 285/75R16. I don't think it's as bad with a Manual Transmission because of the gearing. I get about 18mpg highway.

 

As of now, with the 265/70's i'm getting about 17.5 -18 mpg. And that's driving petty conservative like. You're getting 18 with the 285's?

 

Evil Monkey and your Diferential Ratios are probably different. I would say that your ratio is lower maybe (4.10 to 5.XX) and Evil Monkeys is taller (a smaller Number). I have an 04 Taco 4X4 SR5 4.10 differential V6 and I get 21 Hwy 19 combined. I expect to get 19 Hwy and 17mpg combined. Bottom line, if you put bigger tires on your going to get worse gas mileage

 

Yep. I try to keep all my shifts below 2000 rpm, and run at 62 mph indicated, which is about 65 actual. It is mostly highway driving. I also run premium gas and full synthetic oil (which some have said increases mpg). I ran regular, then switched to premium and saw a slight mpg increase. I ran that for about 1 year. To test my assumptions, I dropped down to regular again and saw the mpg drop to 17-17.5 over 3 tankfuls. Switched back and it rose again to 18.