Tire size and Gas mileage question

[KliersLC]

Howdy,

I had a quick question about tire sizes and gas mileage. I will be taking a 3000-3500 mile trip this summer through washington, Oregon, CA, Utah, Nevada, and Wyoming. I'll only be doing city driving for about 2 weeks in CA, and the rest will be mostly freeway driving with the occasional pass to climb.

Question:

Will my 285 wildcat LTs (d rated) with steelies get better mileage (using a gps for this) than my 265 wildcat ATs (c rated) with the stock wheels?

Things to consider:

1. I will be doing a LOT of freeway driving in the 65-75 mph range on flat(ish) ground--Central CA, Eastern Washington, Nevada, Utah, southern Wyoming, Southern Idaho, and the bigger tires will bring my RPM range down, I am at about 64mph when the speedo says 60. The most efficient speed for this rig is 55-60, so the closer I can get the speedo to that, regardless of actual speed, the better I should do.

2. The steelies and 285s are significantly heavier than the 265s and alloys.

3. I will need to climb several passes, Donner, big horn mountains, cascade range, etc plus I will be on Hwy 1 in oregon for a hundred miles or so, and may stop at the dunes....

So, What do you folks think will give me the best mileage overall?
I picked up about 3mpg in my T100 running the 285s from southern Idaho to Moscow, but I don't know if the same will work on the 80.

Thanks,
Dan



PS, I know that it will be low either way, but with any luck I'll save enough gas to be able to stop off and buy a beer for a couple of you along the way.

 

[cartercd]

Go there with 265s and drive back with 285s and tell us which set worked out better

The heavier weight of the 285s is most problematic when you are accelerating (higher rotating mass), once you are moving the weight doesn't make that much difference.

On the hills you will appreciate the smaller diameter tires, because these trucks are dogs accelerating up mountain passes. The smaller diameter tires will bring your rpms into a more comfortable spot in the power band.

You probably aren't looking at $50 in difference in total fuel purchase, so go with whatever tire you think is safest (age, tread wear, etc).

Have fun.

 

[KliersLC]

I drove the 80 from southern Idaho last weekend, and had to hit 2nd gear several times that I don't usually have to with the 265s, white bird hill and the lewiston grade. Granted, I had 7 people in there with some gear as well, but still....

 

[Kalawang]

I doubt mileage will be significantly affected by the size difference of the two sets of tires. More to your concern, considering that you'll be taking a very long journey, would be the condition, comfort, ( as in road noise ) and durability on the road of the tires used.


Kalawang

 

[KliersLC]

Both sets of tires are at about 75%, Both are pretty quiet being ATs, with the 285s being a little rougher due to the higher load rating.