tire size and MPG

[2shus]

I am running 305/70-16 tires and i have always heard and beLieved that bigger tires would up your MPG. My sticker under the hood says 3. 50 rear end ratio. My speedo gear has been changed and is right on. Does anyone have any input on this???

------------------
1995 Dodge 2500 SLT Reg. cab 4x4 Auto,Long Bed 12 valve, 3. 5 rears, K&N Air filter 112,000 miles Anti lock brk sys, 305/70-16/Mickey Thompson Alum. wheels,Leer cap, Nerf Bars, Black/Black C/D Player Overload springs, Reese Hitch, T. C. Lockup switch, Cats dead, straight pipe.

 

[CumminsAholic]

I put 255/85's on my truck and it upped the mileage by almost 2 mpg. But I have 4. 10s. I think it may hurt if I had 3. 55s because I'd be running out of the powerband. I dunno. Can't say for sure because I haven't tried it myself. But on a 12 valve the power is in the lower rpm's. So it'd probably help.

------------------
1998. 5 2500, 4x4, SB, Red Sport, Agate Interior, Quad Cab, O. H. Console, Auto, 4. 10 LSD, Trailer Tow and Camper Special Packages, Mopar Aluminum Nerf Bars, Spray In Bedliner, Pioneer/Jensen System, 255/85's, Bd Adjustable Preformance Box w/boost module, Boost Elbow, 4" Exhaust Split Into Two 3" w/5" cans, K+N Scotty Style, Exhaust Blanket, Bill K's Valve Body, Mopar Tow Hooks, Front Bumper Step, 55 watt Back-up Lights, Etc, Etc... .

 

[4meseb]

Originally posted by 2shus:
I am running 305/70-16 tires and i have always heard and beLieved that bigger tires would up your MPG. My sticker under the hood says 3. 50 rear end ratio. My speedo gear has been changed and is right on. Does anyone have any input on this???

You guys keep referring to this sticker under the hood that tells you what kind of rear end ratio you have. I must say I've only owned this truck for 1 week but I've looked all over the place under the hood for that info. and can't seem to find it. I bought a 1996 2500, 5 speed, 4x4 5. 9L Cummins Diesel Club Cab. I must tell you guys that I have been a GM guy all my life but was afraid to buy a 6. 5TD and when I drove this truck I fell in love. It's a keeper.
Thanks, Scott

 

[Red Rocket]

The sticker they refer to is at the highest part of the hood when it is open. If you don't have it(it's hard to miss) maybe some body work has been done? It tells you colors axle ratios, limited slip, and a few other features your truck has.

------------------
1998 2500, 12 valves, SLT, auto, 3. 54, 285/75-16, TST 230/605, t/c switch, DiPricol EGT/boost guages,K&N,camper special, 65,000 miles(2/01),
12 ton goosneck!
'01 Polaris EDGE-X 600

 

[grtescpa]

Originally posted by 2shus:
I am running 305/70-16 tires and i have always heard and beLieved that bigger tires would up your MPG. My sticker under the hood says 3. 50 rear end ratio. My speedo gear has been changed and is right on. Does anyone have any input on this???

My fuel MPG dropped with 295's.
Gearing changed and the rear anti-lock brakes
stopped working. Other than that big tires will help in rough terrain. Mine helped when I got stuck in a road ditch at 45 deg angle.
No trouble with the transmission. Still pulls and shifts just fine. Just keep a close watch of your cooler line connectors.

 

[DSiemens]

Has anyone tried the larger Rickson 19'5 inch wheels? How do they effect things?

------------------
95, Kitty dead, #6plate, 5speed.

 

[MLynn]

I recently installed 285's and lost 5mpg. I have 3. 5 rear gears. Thinking about re-gearing to 3. 92 and see if that helps. Anybody have any thoughts?

 

[Cooker]

MLynn,
Is your speedo recalibrated? If not your reading will be lower than actual MPG's.

Was your speedo correct to start with? If it's right now and you were reading high before, obviously your numbers would have been incorrect before the tire change too.

Ryan

 

[John_P]

2shus:

I have a similar set-up to yours, however,
I am running the 285/75R/16 tires. I also have the 3. 54 gears in my truck. When
I first installed the tires, my truck was
stock and I noticed about a one (1) MPG
increase. However, since I had all the
pump mods done and installed the 370's
that increase is gone.

--------
John_P


------------------
Red '96 4x4 2500 Auto 3. 54, TST #5, Major Pump Mods(By "Scheid Diesel") 370 Diamond B Injectors, Gov. Spring kit, AFC Spring kit, Banks Exhaust, Prime Loc, Cummins Chrome Kit,Psychotty Air Filter, Pro-Torque Converter, BD Valve Body, BD Pressure Loc, Isspro Gauges, Sendel 16" Alum Wheels w/ 33" BFGs

 

[Forrest]

I went to 235x85 Michelins & didn't affect the mileage. #ad
But the speedo is now almost right on. I got a Garmin GPS after the 235's & check MPH & was surprised when I found that the speedo was so close to actual. The odometer is off though, according to the mile markers.

------------------
Money Sink - 96, 5 speed, TST 380, HX40-16, 300 HP Injectors, Scourge BD 4200rpm Governor kit, McLeod, 4", CATless, straight out back, chrome turn down, ISSPRO Pillar, Delvac 1 & Amsiol, K&N, Mag-Hytec, 3:54, Michelin 235s on Alcoas, Rancho 9000's, Valentine One.
Dutchmen 27' 5th Wheel.
GoldWing.