Will bigger tires net better mpg on the highway?

[Taurus]

Hello, I am new here and have a few questions: my 2004 Ford Taurus revs kind of high on the express way so I am wondering if a taller tire will help. I know this might throw off my speedometer slightly, but I will adjust my speed accordingly. I have the Duratec engine and it makes great low end torque. I also am aware of possible worse gas mileage in city driving, but thats fine. A taller tire changes the effect of the gearing, and offers less rolling resistance, but will it help mpg in my case?

[CapriRacer]

I think this is going to be a mixed bag.

First, the lower rpm's might help, but the rate of acceleration will drop and you might unconsciously compensate offsetting whatever gain you got.

Second, tire rolling resistance isn't so much size dependent as it is material dependent. That is, it's more about the tire itself than its size. See my page on the subject here: Barry's Tire Tech

[elhigh]

What Capri said.

Often when you go taller, you also wind up with wider. The net result can be no net change, you get the gearing advantage but wind up with more rolling resistance and aero drag. You'd have to choose your new tire size carefully, you want to maintain the frontal area or, if possible, reduce it slightly. That is not easily done. Sometimes trying to find a narrower tire that works requires you get a narrower wheel too, and then things get pretty expensive pretty fast, and for a pretty small result.

When it's time for new tires, shop hard for the lowest rolling resistance you can find. I didn't get LRR tires on my HCH and that was a BIG mistake.

In the meantime, experiment with higher inflation pressures. Some guys will argue against this and they have their points, all I know is that I have noticed these things: it doesn't seem to affect my tire life at all, and I do nearly 20,000 miles per year; the ride is noticeably harsher but not so bad that it is unbearable, and it makes an immediate and easily noticeable effect on my fuel economy. I picked up, if I recall correctly, about 5% on tire pressure alone, and it cost me nothing.

[19bonestock88]

definitely what he^^ said... I've not noticed any major tire life degradation from running at the max pressure listed on the sidewall, and noticed about 3-5% better mileage when I kept them aired up...

Pros:
Sharper steering response
Better mileage
Lower tire temp due to less flex(could actually yield longer life)

Cons:
Rougher ride
Slightly longer braking distances(3% or so) due to slightly easier lockup
Less forward traction off road due to lack of tire flex

[MPGeo]

I've started experimenting with different tire size on my Metro project and as the previous members have stated... It's a give and take. You will have to choose your sizes carefully.

I actually made a spreadsheet comparing data from all the tire sizes available new in the market from sizes 12" - 15" within a specific criteria for my driving style, and based on this just for giggles I chose the tallest option available (within my criteria) and tested it and my reaction was just as what was said, I found that I had to overcompensate on throttle and the gain was surprisingly a total wash - no gain, but my driving style was severely changed and not for the best. But it was a test, and now I'm trying to find my next victim size of tires

In other words it can get tricky and expensive... But there is a potential gain with just the right tire combination, the trick is to find what that is for your gearing and driving conditions. A little research, patience, and used tire/junk yard hunting and you might just find the right one, then you can replace with an LRR tire if your size is available.

[CapriRacer]

One of the problems facing those who want to change tire size in order to get better fuel economy is that a tire's rolling resistance is more tied to the materials the tire is made out of (about a 60% variation) than the tire size (about 5%) - meaning that when someone conducts a test with a different tire size, the tire has to be the same exact model and the same amount of wear in order to eliminate the difference being the make and model of tire. Even tires within the same brand vary quite a bit.

[ECO-AKJ]

Let me know what tire size you have in a pm and I can help you, I sell tires and work as a parts manager at a local ford dealer, I have most of the research on tap, just need a starting point

[mcrews]

You can look at my threads below in my signature box.
I went from 245/45/18 to a 50 series tire...same make and model. Kohmos.
It was about a 5% increase in height.
I picked up more mpgs.
some rules:'
1. you need to spend about 60% of your driving at cruise.
2. stop and go driving does not help w taller tires
3. I found zero lack of power when I went tall. but I tend to drive easy and not in a hurry.
4. try to buy the best lowest rolling resistance possible (but you should do this anyway!)

[Taurus]

I am thinking about going to a 205/65/16. My current tire size is 215/60/16. The new tires would slightly taller, and narrower. And there are lrr options in that size too. I dont think it will effect highway cruising power too much. Right now at 70 mph i am at 2400 rpm. If i could drop that by just 100-200, that would be ideal.

[ECO-AKJ]

Originally Posted by Taurus

I am thinking about going to a 205/65/16. My current tire size is 215/60/16. The new tires would slightly taller, and narrower. And there are lrr options in that size too. I dont think it will effect highway cruising power too much. Right now at 70 mph i am at 2400 rpm. If i could drop that by just 100-200, that would be ideal.

Looks like the 205/65/16 would do it, you would gain a 1/4" of overall height of the tire, if you went with 215/65/16 you would gain 3/4" and would drop close to 400 rpm or so