i'm running a set of 235/85r16's that are load range e at 85psi and have a chance to swap for a set of 285/75r16's load range d. max psi is only 65psi.
the 235's wander,are real stiff, and a bit narrow. can i get away with load range D's and has anyone noticed a mpg difference from E's to D's? i think the height of each tire is about the same so that shouldnt effect ratio's
thanks

 

You'll be fine with a load range D if you don't haul or tow, but I believe you may lose 1 or 2 mpg going to a 285. The 235 you have is probably the most fuel efficient tire you can get. Also, I tend to believe that you'd get better mileage with an E over a D simply because E's are stiffer, not as much drag on the road.

 

The 285's are wider & will give alittle more drag than the 235's,I went from 245,75 to 235,85 & gained .6mpg.
If your truck wanders you might have other issues like the trackbar.
I run 65 psi in the front & 55 in the back & don't have any problems & do air up the back to 70 when towing.

 

Like it was stated above, D's are fine if you drive empty.

The difference you notice in mileage is going to be due to the size change and not the load range. 285's will get significantly worse mileage due to increased wind resistance and increased rotational inertia.

 

I have 285's with a D load range. Each tire is rated at 3300lbs. I belive 235's are rated around 3000lbs. If I am freeway driving I get around 21 or 22 and town I'm getting around 17-19. Thats driving all driving nice and not getting on it to much.

 

I have 265/70/17 and my speedo reads 70mph when I`m going 65mph on my 1995 2500, so it`s hard to tell my mpg when its that far off.
I plan on running a 35" tire, it should almost make my speedo correct.

 

increased rotational enertia sounds like something you should go to the doctor for seriously, that should be good, right? once they get going they keep going or is the term refering to 'getting them going'. in theory, load range, i would think, would play a bigger 'role'. every one goes on and on about checking your air pressure. so shouldnt something that you can keep more air pressure in be better. i wonder what the actual difference would be between 285's and 235's both E load range. (85psi)
i wish they still made 255/85r16's in E's. that would be my ideal but with my budget, i have to use what ever comes up on craigslist.

 

I also like 255/85/16's. They are pricey though. There's two types of friction, static and kinetic. Kinetic friction is the typical friction people think about. Like dragging a brick on top of sandpaper. The other type, static friction, is the friction between, say, a rolling tire on asphalt; or the bottom of your shoe and the ground. If there were no static friction, you would not be able to walk or drive because it would be like you're on super slippery ice. With the 285's being wider, it takes more energy to keep them rolling because their increased surface area increases their static friction on the road. Have you ever tried to ride a bike with really low tire pressure? It takes harder pedaling to stay moving because the whole width of the bike tire hugs the road. 285's are also a little taller and heavier, which requires even more energy to keep them rolling. On the hwy the difference between the two sizes may not be so big, but it should be noticeable in the city.

 

More rotational inertia will not help your mileage. It is comparable to having a heavier vehicle. Yes, you have more momentum once you get going but it takes a lot more energy to get moving. As Newton stated, F=ma which means that it takes more force to move more mass. Once you are moving, the only factors are windage and rolling resistance.

Regarding the higher pressure in tires giving better mileage, it is because it decreases the size of the contact patch. Yes, lower load range tires have lower pressures but there are other factors.

 

who makes the 255/85r16's in E? has anyone had handling problems running the 235's like me? maybe its the type of 235 i have (m+s). my truck wanders a bit.
i would love to get a set of those 8 lug 22.5" rims, so i can put some real truck tires on. anyone have pics of those rims with big rig tires on? i would imagine, if you stuck with radials, those tires would increase your highway milage, being over 33" and not too wide.

 

I have a set of Goodyear G622's on 19.5 rims. Which I feel is the "sane" combination. They are 225's for width, and the load capacity is about 3600 lbs each (I have the load range f's, g's go up quite a bit).

22.5's would just get too big IMHO.

I did have to take off the front mud flaps, the PS was grinding when the wheel was turned the right amount.

 

Yup. Get out the checkbook. Nice, but pricey. I'm looking to get a set of 255's when my currrent tires wear out.

http://www.ricksontruck.com/

 

the ricksons were the ones i was thinking of. very sweet! i especially like the way they look on 2wd trucks. good pics of their wheels on dodge trucks. i dont think even santa can afford them though, not this year anyway.