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Old 07-30-2021, 09:11 AM   #1 (permalink)
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Tire performance vs economy?

Hey Everyone,

I drive trucks. I need them for my work & live. Not the best economy platform....

I currently drive a 2004 Dodge 3500 with 5.9 Diesel ands 6 speed manual.

Now my hauling needs have relaxed and I am looking at a new, smaller, rig. The Jeep Gladiator with the Eco-Diesel has my attention.

Unfortunately, he stock tires are not adequate for my needs. I need better ground clearance and good performance on gravel, mud and snow.

When I upgraded tires on the Dodge I killed my fuel economy. I thought "Taller=better economy". I was mistaken..... Then I figured out rotational mass and moment........

What can you all recommend as the best tire solution for a capable mud and snow tire that will not kill my economy?

I won't fib.... I want it to look good too.......

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Old 07-30-2021, 10:31 AM   #2 (permalink)
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I would reccomend running different tires for different purposes as well as adjusting the pressure accordingly.
For driving on roads, run the sidewall pressure.
For driving offroad, air them down appropriately.

Low air pressure in the tire means the tire deforms more, and has less ground pressure.
High air pressure in the tire means the tire deforms less, wich reduces rolling resistance on the road.
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Old 07-30-2021, 12:44 PM   #3 (permalink)
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How much taller?
When you go bigger the mass increase is small until you get to about 30 or 31 inch tires then every inch you go up in diameter has substantial increases in mass.
I would get a set of rims and have dedicated snow and ice tires.
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Old 07-30-2021, 01:00 PM   #4 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
How much taller? ...
Also, the taller than stock the bigger the affect on your odometer. Did you take into account the % mileage undercount shown on your cluster when calculating fuel economy? I only ask because you didn't mention it. I'm not presuming you don't know this...
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Old 07-30-2021, 02:59 PM   #5 (permalink)
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Imho, the old fashioned semi smooth skinny tires with small tread gaps should do the best, and for that old timey look: on black steel rims. Will it be manly, nope, but that wasn't a choice.
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Old 07-30-2021, 05:35 PM   #6 (permalink)
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Quote:
Originally Posted by Autobahnschleicher View Post
I would reccomend running different tires for different purposes as well as adjusting the pressure accordingly.
For driving on roads, run the sidewall pressure.
For driving offroad, air them down appropriately.

Low air pressure in the tire means the tire deforms more, and has less ground pressure.
High air pressure in the tire means the tire deforms less, wich reduces rolling resistance on the road.

This is excellent advice. I've found that running about 45 psi instead of the factory recommended 30 - 35 psi not only increases fuel economy but also handling because with with higher pressure the tire doesn't deform as much when cornering. (Grassroots Motorsports had a good article on this where they varied nothing but tire pressure and compared skid pad times)

HOWEVER, when we moved to the PNW it took me 3 flat tires to learn that I need to air down to 30 psi when I venture onto gravel roads because we have a lot more sharp rocks on forest service roads here than back East. Knock on wood no flats since I've started airing down.

I went up two sizes on my van. From stock 215/70R16 to 235/65/R16. That dropped fuel economy by 4% 16.6 mpg to 16.0 mpg


For general use on gravel roads and snow I like the BFG Advantage T/A LT. It is a snow rated light truck tire that can be used all year. It isn't a mud tire though. The BFG T/A KO2 might be a good compromise. I know they ride much quieter than most full on mud tires like the BFG Mud Terrain T/A KM3
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Old 07-31-2021, 09:12 AM   #7 (permalink)
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First, OE tires are designed to the specs published by the OEM and those specs have fuel economy (rolling resistance) in mind. They can do that by sacrificing treadwear and/or grip.

Consumers don't generally care for bad wearing tires, so there will almost always be a hit in the fuel economy department when replacing OE tires.

One of the things that affect rolling resistance in tires is the amount of tread rubber - meaning that luggy tires - the ones good for gravel, mud and snow - are worse than all season tires.

Also going larger will help RR - a little bit - but those other things have a much larger effect.

So there you have it. For a heavy duty truck, you just don't have much in the way of options.
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Old 08-05-2021, 09:44 AM   #8 (permalink)
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Quote:
What can you all recommend as the best tire solution for a capable mud and snow tire that will not kill my economy?
Is the vehicle actually used in the snow?

Is the vehicle actually used offroad in gravel etc?

or is it mainly (80%+) used for commute on builded roads on highways?

What is the tire size?
P 255/70 R 18

The majority of wheel options seem to be even bigger. I dont know about thinner wheels on this vehicle but they should be a favorable option.

If the car is used mainly on the road, from the options with standard wheel size I found the Kumho Crugen HT51. - A lot of the other wheels in this size are closer to M/T Mud Tires and thats not fuel saving in any way.


Typical Van Profile, Severe Snow Service Rated. And if realy a lot of snow is a topic in your area carry a pair of snow chains with you.

Last edited by LingLongRaceTeam; 08-05-2021 at 09:55 AM..
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Old 08-08-2021, 04:50 PM   #9 (permalink)
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Quote:
Originally Posted by PNW_Steve View Post
Hey Everyone,
When I upgraded tires on the Dodge I killed my fuel economy. I thought "Taller=better economy". I was mistaken..... Then I figured out rotational mass and moment........

What can you all recommend as the best tire solution for a capable mud and snow tire that will not kill my economy?
If the fairly road-oriented stock Gladiator tyres don't do it, you're going to take multiple hits in fuel efficiency anyway ...

Bigger tyre (even with same rim size) and more mud or offroad oriented, that is going to:
be heavier - HIT #1
worsen your aero by lifting up the body - HIT #2
increase rolling resistance through its more open profile - HIT #3
increase rolling resistance through lower tyre pressure - HIT #4

Essentially the opposite of what folks here are shooting for


I guess your best shot is asking at a Jeep / offroad forum - but they generally don't have a tyre's FE high on the priorities list

For overlanders -especially Ozzies- FE might be more a thing, as it defines their range and autonomy.
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Old 08-09-2021, 03:02 AM   #10 (permalink)
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I think the biggest hit of big tires is the height. Know the manufacturer doesn't have to publish differnt MPG ratings for off road packages with bigger tires or other add ons that obviously will effect real world MPG. So a Rubicon Gladiator supposedly gets the same MPG as a basic sport, or a Sasquatch Bronco is the same as a base as long as the engine and transmission are the same. Of course that's not the case in the real world.

Anyway big tires and the also added lit kit needed for big tires is like adding a big cargo box on the roof. Don't think more air will just pass undisturbed below the truck because the underside of these things is just an aero nightmare. So with a lift kit and big tires you hurt any factory tricks to improve the coefficient of drag like say a front air dams proximity to the ground, all while adding overall frontal aera for significantly more overall drag.

PS I'm in western Montana and used to have a 2004 2500 5.9 6 speed Cummins 4wd and it was plain terrible in the mud sand rocks and snow compared to my stock 2009 Jeep Commander with the Quadradrive 2 and e lockers front and rear. Now I've added a 3" lift and 32" tires and it's crazy better than the Cummins off road. The Stock Rubicon Gladiator already has 33" tires and lockers front and rear and will be much better than your Cummins. So get and Ecodiesel and with some basic ecomodder tricks you will beat whatever EPA rating they have which I think is high 20s MPG.

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