Taller tires for better MPG ?

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Stock size is 245/75-16
If I go up a size to, let's say, 245/85-16s will I get better gas mileage?
I'm not looking for much, but if I have to change the tires why not
move up to a size that might help. I don't tow, I just carry tools and sometimes some job site materials (concrete, gravel, etc).
I know that increasing the unsprung wheel weight will hurt MPG, so I want to go taller not wider, I would love to buy lighter wheels, but I think that would get too expensive. If you think otherwise please tell me where to get cheap light wheels (still load D or E though).
From:
http://www.miata.net/garage/tirecalc.html
Diameters:
Stock is 30.5 in
With 245/85-16s I'm running 32.4 in (6.3% increase and with toyo tires, I gain 1 pound)
With 255/85-16s I'm running 33.1 (8.5% increase - limited tire choice).
I could also go with 17s (they are all over ebay), but I think I'll gain more unsprung weight.
Of course I'm stuck with "highway" tires, but that's fine. This is a work truck so I don't take it off road.
I know the saying, you bought a truck accept your MPG, I'm not crazy about improving my mileage, but when I HAVE to replace a part I always try and upgrade it as best as possible.
BTW: what highway tires do you recommend?
thanks
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Peter,
You bring up an interesting idea, and I'm curious to see if anyone has concrete info from experience.
So the engine turns 8.5% slower with the new set up, right? Let's go with what I think is an optimistic increase in mileage of 5% -- over 40K miles (arbitrary lifetime of work truck tire), that's burning 3077 gal of fuel stock, 2930 with bigger tires. 146 gal. @ $2.50 (ya right) is $365 bucks.
My point is that if you're trying to be ecologically sensitive, then ok, give it a try. If you're trying to save money, then maybe there's an alternative.
I don't know what you're looking to pay, but stock truck tires are practically given away by the tire shops around here....$70-90 for med. duty set of 4 mounted and balanced, like new condition. You get name-brand quality in construction and name brand ride.
Taller tires are also harder on your brakes and will work your tc or clutch more....
Of course I did the same thing I'm recommending, going with a set of 17" take-offs -- a little taller, yes more rim but less tire. Tough to beat OE Michelins IMO for 5 on rims at $100. Sorry if that's too off-topic or off in the wrong direction.
Jon
snipped-for-privacy@yahoo.com wrote:

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On 2 Oct 2006 10:15:23 -0700, snipped-for-privacy@yahoo.com wrote:
Theoretically, it would seem that having a taller tire would change the "gearing" very slightly and give you better mpg on the highway...
Our Ram had 245/16 on it when we got it... the door sticker called for 255... We went to 265/16 and didn't see a mileage difference, but didn't really track it before the new tires..
NOTE: changing tire size WILL throw your speedometer and such off... ours reads 60 when we're doing 63 mph... I'm guessing that it was off by the same amount in the other direction before... If so, the odometer would tell you that the mileage was better with smaller tires because it registered 4% faster/further than you actually went???

Mac
https://home.comcast.net/~mac.davis https://home.comcast.net/~mac.davis/wood_stuff.htm
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Your idea is sound, but will be harder on equipment, because of the gearing change. Another way to save gas is to buy Load Range E tires. These tires can be inflated to 80 psi, and then you will have less rolling resistance, with the same gearing.
Remember the difference on a 10 speed bike between 60 psi tires and 100 psi tires, if not, go test a bike at a local bike shop - and really save some gas!

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I believe the 80 pounds is when the truck is loaded to it's max. Operating at 80 pounds m/t isn't going to put much rubber on the road and the truck will ride hard as hell imo.
Roy
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I can't tell the difference in ride at 40 psi or 80 psi. on my 98 Ram 1500 SLT Larime. Of course, it ain't the best ridin' truck, anyway! But I do get another mpg or so (depends on how much highway crusin' you do.)

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I guess my ass is more sensitive than yours.<G>
Of greater concern is the stopping ability of your truck with the 80 pounds in the tires and m/t. You have a much smaller patch of rubber in contact with the road.
Roy
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You bet it is!!!!

Stopping???? what's that????
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And it's cute too!<BFG> There's a gimmie for wide ride
Roy
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Mac
https://home.comcast.net/~mac.davis https://home.comcast.net/~mac.davis/wood_stuff.htm
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Gotta tell ya story bro. For me heated seat's are dangerous. I've worked nights most of the past 30 years and never had a problem staying awake while driving. I had left the truck at home and taken Sue's eldo, at about 3:30am on a cold Feb. morning I'm driveing along and figure let me try these heated seats. 5 minutes later I'm thinking these are real nice sooo comfortable. 10 minutes later I catch myself nodding off. Too comfortable. Had the same thing happen a few weeks later. Those were the only times I had ever nodded off while driving. Never, ever will you get me to use them again Yup, I do have a sensitive ass.<G>
Roy

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hmm... opposite of brain freeze?? Mac
https://home.comcast.net/~mac.davis https://home.comcast.net/~mac.davis/wood_stuff.htm
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Roy wrote:

Just don't crank up the heat in them after visiting the Chili and Hot Wings diner.
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While it is true that 80 PSI is required for max load capacity, there is benifits from increase average presure from reduced rolling resistance which can improve MPG. The only real draw back is a stiffer ride on a bumpy road. Tread design and profile plays a roll here too. A 83 series tires (like a 235/83/R16 E) will have less drag and rolling resistance than a 70 or 75 seris. It is also about 1 inch taller than a 245/75/16 too. Finailly, the tread design itself plays a roll too. A smooth tire with little or no cleats will consume less power than one with a "meaty" tread. (look at a semi tire sometimes) Genrally unless you are carry enough weight to need it, there is little or no gain in MPG with pressure over 55 to 60 PSI so even a D range tire running at or near max pressue will roll nicely with a smooth tread. ----------------- TheSnoMan.com
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Where do you find a tire with an 83% aspect ratio??? or 83 series as you call it?
oh and while I'm asking questions.....you find that knock sensor yet?
just wondering.
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Well, well, look what crawled under the door. Tired of spreading false info at the other group and decided to drag your ass back here? First you have a few questions to answer from the last time you were here. You remember them don't ya? Or are you here for another reason, I figure there is another reason.
Your sig looks good.
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Oh, you didn't address the stopping issue with over inflated tires. Care to take a shot?
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The key is 'overinflated'. The tires are not 'over-inflated'; they are inflated to spec.

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Really? So it is your position that filling your tires to max air pressure and running the truck with no load does not present a over inflated condition with regard to braking and handling? Am I correct in my understanding?
Roy
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https://www.tiresavings.com/tireShop.php?action=findMan2&manufacturer=Michelin&tirename=LTX+A%2FS&seasonI own a set. I know what they do.

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