slightly bigger tires=super bad gas mileage?

[andyblack]

I agree that aggressive tires will cause increased fuel consumption. Think about it. If your tire is providing more traction (which is why you went to the more aggressive tire, right?), then the tires will stick to the ground more, thereby causing you to have to give the engine more throttle to accelerate the truck. It would be like going around with your brakes dragging, only not nearly that drastic.

One obvious thing also: Have you checked for fuel leaks? The gas could be leaking out or evaporating before it has a chance to burn. Remember that cold weather makes eveything contract. Could it be possible that a fuel line or fitting has rotted or come loose?

 

[Merv]

Did you adjust your speedometer to compensate for the difference in size. A bigger tire will "fool" the speedo into giving you better than expected mileage. I'd expect that your corrected mileage is definitely worse.

Later,
Buddy

Yeah i have. Used mile markers and adjusted accordinly.

The aggressiveness (tread pattern) of a tire definitely can affect fuel mileage. More aggressive tread patterns have more rolling resistance, and are usually heavier, which makes fuel mileage worse. [/quote

I agree that aggressive tires will cause increased fuel consumption. Think about it. If your tire is providing more traction (which is why you went to the more aggressive tire, right?), then the tires will stick to the ground more, thereby causing you to have to give the engine more throttle to accelerate the truck. It would be like going around with your brakes dragging, only not nearly that drastic.

One obvious thing also: Have you checked for fuel leaks? The gas could be leaking out or evaporating before it has a chance to burn. Remember that cold weather makes eveything contract. Could it be possible that a fuel line or fitting has rotted or come loose?

Tread type has nothing to do with it. A heavier tire will affect it sure. But type no. Mud tires do not stick to the road because of their aggresive tread. If anything they have less rolling resistance. They have less tread actually contacting the road. They are also typically a fairly hard compund.

 

[6.2Blazer]

Tread type has nothing to do with it. A heavier tire will affect it sure. But type no. Mud tires do not stick to the road because of their aggresive tread. If anything they have less rolling resistance. They have less tread actually contacting the road. They are also typically a fairly hard compund.

Believe what you want, but if everything else is apples to apples besides the tread pattern, then more aggressive = more rolling resistance = worse fuel mileage. I'm just not making up some hypothetical answer in my mind as I work for an automotive test facility and do fuel economy studies a large part of my time at work.

Maybe back in the '70's the tires like Ground Hawgs had a really hard rubber compound but not the vast majority of modern tires. Now granted, I definitely don't agree with the comment about aggressive tires sticking to the road better. However, again with everything else being apples to apples, more aggressive tread patterns wear quicker on the pavement and are louder......both of these are indications of more rolling resistance. Faster wear means more scrubbing and tread deflection, and tire noise is also an indication of the lugs slapping the ground and causing resistance.

 

[blazinzuk]

not to hijack the thread but and 6.2 all respect to you I realize you do this for a living I am just trying wrap my head around this,

Given the same rubber compound a tire with 50% less rubber touching the road is going to have more resistance than a tire that has more rubber hitting the road?

I realize that there are probably too many variables for this to be a completely true statement but in my (sometimes weak) mind I would think that the same tire with less rubber on the ground would have less rolling resistance.

 

[blazinzuk]

never mind a bit of research reveals that I am totally wrong a tire to have the same rolling resistance as a milder tread would need to have a harder rubber compound

 

[andyblack]

Let me clarify. I wasn't suggesting that the more aggressive tires would actually "stick" to the pavement more (like tape or something). "Greater rolling resistance" is the term I was looking for, I just didn't word it properly. I was just saying that a set of mud terrains would require more throttle to accelerate and keep rolling than a set of all terrains of the same size would. If this weren't true, why wouldn't brand new trucks come with mud terrains? Regular light truck tires intended for the highway aren't that much cheaper, and most of today's mud terrains aren't that loud on the road. New trucks come with mild treads because they handle better in most situations that a new truck owner is likely to encounter, and because they get better mileage and wear better. I'm saying that if super aggressive tires have no effect on mileage, there wouldn't be much of a market for milder, more street-friendly tires. Everyone would be running Boggers and Krawlers on their daily drivers and no one would have BFG All Terrains, but which one of those three do you think they sell the most of?

 

[bigtruck1]

Gravedigger472,

My guess,, is that of your 4.8mpg loss,,, 1-1.5 of that is due to the newly introduced innacurracy of your odometer (result of the tire diameter increase--- you are traveling slightly further than what your odometer indicates),,, so in other words,, you didn't actually lose that 1-1.5mpg... The other roughly 3.5 mpg can mostly be accredited to the temperature change you've experienced,, and a small part due to the increase tire diameter/weight (requireing more energy to get ya rollin).. Everyone is absolutley correct that there are MANY other variables that affect fuel efficiency and GPM calculations; however,, i think in your case it can mostly be contributed to odometer innaccuracy and temperature... You may try adjusting your cooling system when you expect the ambient temp to drop significantly, in attempt to maintain optimum running temperature (and achieve more desirable fuel efficiency)... Running temp, of course, can be controlled in variety of ways;; the easiest being thermostat,, fan kick on/off settings, radiator covers/partial-covers, etc)... Just some ideas... Hope this helps

One more suggestion--- changing to a lighter weight oil in the colder season could improve your gas mileage as well... Also, mulit-grade oils (ie- 10w40, 5w30, etc) are impacted less by temperature change than single grades... So you might see a noticeble fuel efficiency improvement by switching to a light weight multi-grade oil like 5w30 during a cold winter... (perhaps in conjuction with above mentioned cooling system adjustments..)

Okay,, one last thing related to temperature--- This one is VERY SIMPLE,,, but often overlooked... Temperature has a tremendous impact on tire pressure.... Keep in mind,, that for every 2 psi that your tires are underinflated, your mpg decreases by 1%...

 

[djtejas]

A bigger tire will "fool" the speedo into giving you better than expected mileage. I'd expect that your corrected mileage is definitely worse.

Later,
Buddy

Actually, the opposite...a bigger tire will make the speedo read lower mph and lower mileage than the stock tires...it would look like a decrease in mpg when you calculate the miles driven.

I have 32"s and I'm actually going 65mph when my speedo reads 60mph. Therefore, I'm putting less mileage on the speedo than is actually being driven.

 

[Jessie James]

Okay, I admit it, I have been stealing gas from your tank.

Get a locking gas cap buddy!

 

[gravedigger472]

dangit shoulda known. lol. that better not be happening

 

[Blue85]

An aggressive tire creates more noise and vibration on the road. It requires energy to do this - which comes from your gasoline. The "amount of traction" is irrelevant because in normal street driving, all tires are providing 100% traction - they are not slipping.