Comparing MPGs: Tire Diameter VS Weight

Hey guys, new to the forum here. I have looked far and wide without much of a clear answer. I’m trying to decide between 275/70 17, and 285/70 17 in the Falken Wildpeak at3w, however the 275 is a C rated tire coming in at 57lbs each. The 285 that I’m looking at is P rated, and only 50lbs.

I spend most of my time on the highway in my daily commute to work, so MPGs are pretty important, but I do want to look cool also, which is why I’m upsizing!

So the question is; would I get better MPGs out of the 285s, being 7lbs less per tire, or the 275s because of the 0.6” height difference? Thanks in advance!

 

Yup, that's a hard question.juat to give an idea for the weight catagory. I have 235/75/15 and I went from a 25 lb tire to a 36 lb and my mpg dropped by 3, 22-19

 

I've been buying tires since the 1970's and have never noted a correlation between tire weight and fuel mileage. I have noted a difference with wider tires and tires with more aggressive tread losing 1-3 mpg compared to narrow tires with a less aggressive tread. Taller tires also effectively change the axle ratio and force the engine to work harder. But in my experience as long as you stay within 1-2" of the stock size the difference is minimal.

My Tacoma came with P rated 265/70/16 tires that weighed 38 lbs each. I've been running E rated LT265/75/16 tires that weigh 53 lbs each for several years. The E rated tires are 1" taller, same width, and with a similar mildly aggressive All Terrain tread. My fuel mileage is exactly the same as it was 13 years and 204,000 miles ago.

In my experience expect 1-3 mpg fuel loss with either tire. Both are wider and taller than stock with a more aggressive tread. I doubt if it would make much difference, but the wider 285 will probably hurt fuel mileage the most. Seven pounds of weight is a non-factor

 

This answer seems very correct. I didn't even think about my more aggressive tread.

 

I went to 285s and I gained mpg

 

@ 28 lbs diference, I'd be like having your dog with you on the trip!

I'm guessing the wider the tire, the more drag.....

 

Difference is that it is rotational and unsprung weight and it acts very different. Think of it like wearing a 28lbs backpack going for a jog vs having 28lbs weights strapped to your ankles.

 

I do not think anyone can accurately answer your question unless they have tested fuel economy with both tires. I also think people put too much emphasis on tire weight and diameter. A rolling tire heats up when it flexes and this energy is then dissipated into the environment; much like a brake. The amount of energy loss is a function of many things including rubber compound, amount of rubber, tread design, etc. Weight by itself does not affect this, but it can be correlated with the amount of flexing rubber in the tire.

It's true that since a tire is rotating that it contains both translational and rotational energy unlike the non-rotating parts of the truck, but the tires are very light in comparison to the entire truck. Also this energy is not really lost until you hit the brakes.

Here is some discussion of the topic.

https://ecomodder.com/forum/showthread.php/effects-wheel-tire-rotational-energy-25197.html

NHTSA Tire Fuel Efficiency Consumer Information Program Development: Phase 2 – Effects of Tire Rolling Resistance Levels on Traction, Treadwear, and Vehicle Fuel Economy
https://www.nhtsa.gov/DOT/NHTSA/NVS/Vehicle Research & Test Center (VRTC)/ca/Tires/811154.pdf

With that said, I’ll take a guess and say the p-rated tire will provide better fuel economy than the c-rated because it’s likely to have less rubber that is flexing per distance traveled.

 

OP, If you are not lifted, I'm pretty sure those tires will rub.

G.

 

Aside from what's been said so far, this will depend on how you drive. If you're doing a lot of highway driving, and don't accelerate aggressively, you might not notice a big difference with either tire.

On the other hand, if you do a lot of stop and go driving, and always flooring it to get up to speed, you will notice a big difference.

I just switched from 265/70/17 KO2's @ 45.55# apiece to 285/70/17 Toyo Open Country AT3's @ 55# apiece. Around the city, I seem to have lost about 2 MPG. On a mini road trip last weekend, I got pretty close to normal fuel economy as measured by the odometer, which is impressive considering they're 1.1" taller and 10# heavier than the KO2's.

This is just my experience so far. YMMV

 

For highway driving a wider tire will get less mileage , a taller tire will get less mileage and make your truck less stable. Keep in mind tires with less offset (sticking out farther) hurt highway mileage as well. If you don't need the clearance for off roading consider something less extreme, you can make your truck look much cooler with a mild size upgrade without losing too much mileage or stability on the highway.

 

According to your Taco's readout or actual measurement?

 

Actual measurement. I drove X amount of miles and used X amount of gallons of gas. When I did the math, the readout was almost 2 mpg less than what I actually got

I used GPS to find out how many miles I actually drove, not the trucks readout

 

Close but put it a little more in perspective, 28 lbs on a 4000 lb truck vs ~1.4 lb strapped to a 200 lb man's ankles...it's not noticeable.

 

I went from 245/75/16(3ply) to 235/85/16(10ply) and lost 4mpg.

 

Then Michelin Defenders, in OE or +1 size is where you want to be.

Sometimes not all the boxes can be checked. In this case the 'cooler' you look the more TCO will rise.

 

1.4 pounds strapped to a 200 lb man is not noticeable? I would have to disagree. Since I started competing in triathlons a few years back and I have become aware of every ounce or gram of weight I am carrying.

 

Again, are we talking about a track car that every ounce is noticeable or a 4x4 truck that will end up with more than the weight of the tires easily in worthless upgrades? Yes, every pound counts, but get real, a couple pounds at each tire isn't going to dramatically impact fuel mileage. As mentioned earlier, the extra width, which creates extra friction will impact mileage more than anything.

 

I think any difference in economy from tire weight for the same diameter at highway speeds is more likely from tire stiffness. If the tire is rated higher, it's stiffer and more energy is lost as the contact patch makes its way around the tire - effectively squaring off a circle. More aggressive treads do the same thing with the blocks of tread causing local spots where its stiffer compared to the space between treads. A wide tire means a larger contact patch = more deforming rubber every rotation, more energy loss.

You can tell tires lose energy because they "warm up" with use - literally energy from your engine imparted into the tire.

 

If your worried about 1-3 mpg you have no business getting bigger tires, it comes with the game except it or don’t.