Downsizing tires effects on fuel economy

[GOOSE]

Have you looked at the Toyo M55 tires? They are quite expensive but wear like iron and come in the 255/85-16 size.

http://toyotires.com/tire/pattern/m-55-commercial-truck-tires

I was running 305/70-16 Nitto Terra Grapplers that were shot and was getting 14 on average. I put a used set of the same size Mickey Thompson mud tires on and my mileage fluctuated greatly for some strange reason. I did go from a load range E tire to a D tire and wonder if that has an effect on mileage. I am currently using Toyo M55 235/85-16's and consistently get 14-15 mpg's, right whee the 305 Nittos were. This is mostly around town and rural driving.

If I could get 18mpg with 315's

 

[Dave7.3]

I still don't understand the fascination people have with shelling out a little extra to have big fat tires. Why not just buy the tire size that your truck came with stock? 235/85/R16s seem like plenty of tire to me.

I get my tires through: http://www.tirerack.com/

EDIT: Forgot to add, are any of those others sizes load range E to begin with? I know the previous owner of my Super Duty was a cheap ass and threw some load range C tires on that were 255/65/R16s. They do NOT look happy on there either.

 

[chevytaHOE5674]

235/85/16 E's are usually only rated for 3040 lbs.

265/75/16 E's are usually good for 3400 lbs.

285/75/16 E's are usually good for 3700 lbs.

IMO that is all the more reason to step up from the stock 235/85's.

 

[Dave7.3]

235/85/16 E's are usually only rated for 3040 lbs.

265/75/16 E's are usually good for 3400 lbs.

285/75/16 E's are usually good for 3700 lbs.

IMO that is all the more reason to step up from the stock 235/85's.

Thanks, I didn't know that!

 

[Brad S.]

A few years ago I had 265/75/16 on, then went back to 235/85/16, didn't notice a mpg increase or decrease, a very small rpm change.
But a question about the 255/85/16, would they fit under a stock suspension with saggy front springs??
The 265/75/16 almost didn't work, and if I remember right the 255/85/16 is a little taller.

Just double checked the 255/85/16 is 1.34" taller than the 235/85/16
And the 255/85/16 is 1.42" taller than the 265/75/16
(thanks for the link jwalterus)
For mpg remember if you can put your truck on a diet, I weighted my tailgate once, somewhere around 70-80lbs.
Stock steel wheels with 235/85/16 tires are close to 90lbs each. (this was a couple years ago too)

 

[Fordsandguns]

clicky linky ----> http://www.1010tires.com/tiresizecalculator.asp

Thanks! That went into my favorites.

 

[PwrSmoke]

I'm not hearing anyone talking abut correcting the speedometer. My truck's speedo was off when it was bone stock and brand new! It was reading more speed and more miles travelled by close to 9 percent. By calculating a correction for the OE tires and using it when I checked mpg, I lost 1 mpg... just like that. When I went to 285/70R16s (a 33") the speedo was corrected to within 2 percent. Mileage didn't get any better though, because the tread pattern and tire width more than ate up what I gained with the diameter increase. It's an AT tire.

Tread pattern is about 65 percent of tire rolling resistance, with a mild highway tread having the least followed by an all-season, an AT and a MT. In fact, on my other Ford, I did a mpg test between the two tires in the pic below, a Michelin LTX AS and a **** Cepek FCII AT. Identical size tire on identical rims, tested on a carefully chosen 182 mile course where all the starts and stops were mapped out. Even went tot he trouble to make sure the engine and axle oil temps were the same before each test, which was run the same afternoon. The difference in mpg on this mixed course... 2.4 mpg. In the almost three years since that test, the mpg has averaged 2 between these two tires. I run the ATs in summer and the AS in winter or on long trips. SOme test done by the Tire & Rubber Assoiation show as much as a 60-100 percent increase in rolling resistance between an aggressive tire and a highway tire and for every 10 percent increase in rolling resistance, there is a loss of 1-2 percent of fuel economy.

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[4 tone f250]

Thanks for all the help I think when I can afford it I'll either switch to the 35x10.5 boggers since they're slightly over 35 tall and narrower and still over 3000lb rated or I'll get the tires I really want 35x12.5 mud grapplers from what I've read they wear really well on heavy trucks and are rated around 3700lbs if I remember right and I do go off roading enough that I'd prefer to keep good tr action and not lose any clearance and from what I get from you guys that makes sense going smaller will only hurt my mpgs anyways so when I want better mpg I should be able to get my hands on a good m90 or m112 and put that in and I may experiment with propane injection too I'm starting diesel industrial classes at uti soon so I should have no problem doing what I want lol but thanks you guys have been quite helpful in keeping me from making a dumb decision just to make a quick buck lol

 

[chvycmnslvr68]

Have you looked at the Toyo M55 tires? They are quite expensive but wear like iron and come in the 255/85-16 size.

http://toyotires.com/tire/pattern/m-55-commercial-truck-tires

I was running 305/70-16 Nitto Terra Grapplers that were shot and was getting 14 on average. I put a used set of the same size Mickey Thompson mud tires on and my mileage fluctuated greatly for some strange reason. I did go from a load range E tire to a D tire and wonder if that has an effect on mileage. I am currently using Toyo M55 235/85-16's and consistently get 14-15 mpg's, right whee the 305 Nittos were. This is mostly around town and rural driving.

If I could get 18mpg with 315's

If you would change out those 4.10's for some 3.73 or 3.55 ratio you would go to low to mid twenties ... if your running a manual o/d tranny like a five speed .. also remember that width is a very important factor with tires when considering fuel mileage ... the wider the tire the more rolling resistance ...My 91 Chevy in my profile pic gets around 26 hwy and 18 city if i keep my foot out of the fan ...

 

[GOOSE]

I'm hoping to get a Gear Vendors in my truck at some point. I think that will be my best all around win as far as performance and economy goes. I am towing with 4:10's and 235/85-16's right now and can't imagine doing something that will take away from the towing ability of my rig.

Tranny rebuild, kevlar clutch and a spanking new GV will be sweet. Maybe in another couple of years.

 

[chvycmnslvr68]

As far as towing goes your actually better off with higher gears .. I used to drive truck and the best pulling trucks i ever drove had the highest gears ... there is less drag in the rear diff the closer that you get to a 1-1 ratio...i just pulled a 40' goose-neck trailer over 4400 miles and it was loaded very heavy ... and my truck has 3.73 gears in it ... you just have to shift down slightly sooner is all ...
I used to have a small gear vendor o/d unit in my truck and with the 3.73 gears and the 5-speed o/d manual tranny it went from 26 MPG to over 32 on HWY ... and with a little H2 introduced into the intake I had my truck up to 127.4 MPG ... yes the one in my profile pic
I am currently replacing my engine as i am having fuel pump problems ... typical with an old rotary pump with over 400K on it .. and then I am going to get an O/D unit that will stand up to the Cummins and begin testing and documenting my MPG results ... I should be able to achieve around 150 MPG based on what I have already achieved
I expect to get over 200MPG with my Toyota 4-Runner with the gear vendor I already have installed in it along with a little H2 ... It has a 2.2 liter diesel Isusu engine with a turbo and gets around 47 MPG at this time with just single O/D and running on straight diesel ... It should be intertesting to see just where I can get it to as far as MPG's go ...

 

[NTOLERANCE]

swap rear axles to 3.55 and run stock 235/85/16 for best overall mileage gains.
the issue with going with taller tires is,it raises the truck which introduces more air under the truck where aero is horrible.
now combined this setup with a custom low front air dam,and you should be able to pop up from 18 to 20+
you should really consider a zf5 or e40d swap too.whatever the cost,if you plan to own the truck and drive often,is payed back in little time at these fuel prices.long gone are the days of driving a truck without over drive.

Is the air dam you were talking about shown in your avatar pic?