You will see a small gain in mileage,but nothing huge,at least not a big enough offset to pay for the new tires.

If you want a good snow\ice tire,look at the Cooper Discoverer M&S.

 

Thumbs up on the coopers!

I have cooper m&s on the wife's subaru, very good all round tire. For the truck I am considering those or maybe bridgestone revos or there is another tire advertised in 4x4 mags, it says it is m&s rated, 50k miles and E load range. I'll have to look that up now....

 

I have Cooper ST's on my K25 and they are a nice all terrain tire. They are very good in the mud too. The best part is they have a 50K mile warrantee and are MADE IN THE USA. Support American workers. Your job depends on it.
Mike

 

the cooper m-s is by far the best winter tire out there, i sell a good many at work and everyone loves them, i run cooper s-t in the summer for the looks

 

some posts to read

Rdsealey

Below are some good reads on tires and IMO the 235-85 in the E range is the way to go. They wont be any taller than your 265-75 so you wont see any improvements due to that but you can run them a lot harder and the thinner profile should help a little. As Chris said you wont see enough to out weigh the cost of tires or anything like that but once again IMO I think the thinner tire will save wear and tear on the front end they don’t seem to cup as much and if rotated regularly will wear very well. The big thing you will see when reading below there are two schools of thought below. The guys that want a year round tire with excellent winter traction and the guys that have dedicated winter tires. And switch them out spring and fall. That’s really the first decision you have to make before you even go tire shopping. If you want to have spare rims and switch tires for maximum performance then I don’t think you will get much advice here other than the “cooper Discoverer M&S” and a few guys speak highly about the “Green Diamond” with dedicated snows your choice of a summer tire will also be different that the all season tire I would think depending on what you do in the summer with your truck. Offroad or just highway. Now if you want a year round tire in the 50 to 60 k range then you have some reading to do. Cooper, BF Goodrich and Bridgstone Revos you mentioned are about the top three I see talked about here.
If you click on the threads below there are posts with all the links you need in them to go to the manufactures web pages tire rack etc

Good luck and post back with what you get
Bud.

http://www.snowplowing-contractors.com/forums/showthread.php?s=&threadid=3976

http://www.snowplowing-contractors.com/forums/showthread.php?s=&threadid=4246

http://www.snowplowing-contractors.com/forums/showthread.php?s=&threadid=4068

http://www.snowplowing-contractors.com/forums/showthread.php?s=&threadid=4554

http://www.snowplowing-contractors.com/forums/showthread.php?s=&threadid=4663

http://www.snowplowing-contractors.com/forums/showthread.php?s=&threadid=5569

http://www.snowplowing-contractors.com/forums/showthread.php?s=&threadid=5606

 

You wont gain enough in mileage to make it worth swapping tire size. I think the truck is actually doing great at 10-15mpg considering it has 4.10 and no overdrive in the trans. Consider yourself lucky.

 

What type of setup do you have? Is it a stock 350? and what carburator do you run? Is it a quadrajet or aftermarket? What kind of driving are you doing when you get 15 miles to the gallon with this truck? I have an '82 K25 with 285/75/16 Cooper st's and 3.42 gears and the best I have ever gotten with it is 13mpg. That was traveling at 55 on the highway on a day without much wind. I would like to compare. If I can go to 4.10's like you have and not lose any mileage I would do it in a heartbeat.
Mikebb

 

one other thing to consider, your mileage is probably higher than you think it is, if you are running over size tires your speedo and odo are reading slow, i run 33 12 50 15 in the summer and go to 265 75 15 in the winter, if i check the mileage i gain about three miles to the gallon with the smaller tires, i am sure most of that gain is because the speedo is running closer to the factory with the smaller tires on

 

WOW! I didn't realize that this would generate this many answers

Ok to answer some questions about my set up.
I have a K20 85. The engine is a GM 350 Goodwrench crate engine for now. The carb is an edlebrock 600 (1406). The drive train is stock, with 4.10 gears and an SM465 standard tranny. The best milage that I have measured was 16 mpg. I was towing my wife's subaru after it blew the head gaskets in Washington State. I had the outback on a flat bed, it was like 5500 lbs. I got good mileage because I going slow, like 55 mph over Independence pass in Idaho. On a trip in 03 from Bozeman montana to Denver Colorado I averaged 12 MPG but that was because I caught a blizzard coming out of Denver. It was a century storm. They closed the interstates in Wyoming so I took to the back roads. I felt really good about getting that kind of average for the trip when I spent half of the return trip in 4wd. At that time I had the quadra jet.
Also, I think that the odometer and speedometer are accurate because I had a GPS unit that was showing average speed and it agreed with the displayed numbers on the speedo in the truck.
Maybe I am just getting luck. If anyone wants specific information I can keep better information over the next couple of months.
As for the tires, I found out a local dealer special ordered a set of Revos for someone else and now that person bailed. I might be able to get them for a good deal but I don't know. For the past two days, the tire has held air. The tires I have are Firestone Wilderness ATs. I paid $100 for set, they were used. I mounted them at a local garage. The main drawbacks for the current tires are that they are C load range. My plans for the use of truck are to either get a Toyhauler and haul the bikes in it or get a slide in camper and get a trailer for the motorcycles. At that point, I will replace the tires one way or another. I should not have hauled the Subaru with them, too much weight or the rear. With the slide in and trailer, the tires will be above max I think.
As far as why my mileage is what it is I don't know. The speedo might be off, but I don't think it is because I checked it with a GPS transceiver. I usually don't go too fast in the truck, like 65 on the interstate. This keeps the RPMs to about 3k.
Hope this info helps. Also, I really haven't spent time with the carb, I need to tune it right. I put it on the truck without and jetting or metering rod changes. I should have made a couple because of the weight of the truck and the altitude.

Robert

 

http://www.powerdog.com/tiresize.cgi

will allow you to compare overall sizes. I used it to figure out if my odo/speedo was reading correctly...

 

a little more information about my driving style and area

I don't drive my truck very fast at all. I take my time and slow down at lights, I try to drive very smoothly. If I want to go fast I have a motorcycle to take care of that need. In my truck, everyone passes me. Also the road that I travel to work daily is on a valley floor. There aren't any hills on my 25 mile, one way commute. Hills seem to make a big difference in mileage for me.

 

So, overall, what is your average mpg driving back and forth to work? Did you keep track of what happened to mileage when you went from the Qjet to the edelbrock. Conventional thinking says that if it is in good shape, the Qjet should get better mileage.

 

11.7 MPG

measured over about 600 miles, the mileage that I am getting averages to 11.7. 200+ of those miles were in 4wd, as it started snowing here. I think my previous post of 15 mpg was optimistic.

 

Istill consider 11.7 to be good when you take into you were in 4wd,and the gear ratio and lack of OD. My 91GMC only gets 11-13 and its got 3.73 gears,31" tall tires, and a .70 OD.It runs at about 1600 at 55mph.If i cruise gently in the interstate and its flat i can get 15 out of it,but for most of my driving its 11-13.