I was talking with the Tire Rack rep and he said that if I increase the diameter of my tires my mileage will decrease and that the stock tires on my '08 Sierra 2500HD will give me the best mileage.
But I think if the the tire size is increased (so the distance travelled in one revolution increases) and the width stays the same, (friction doesn't increase) and I have plenty of torque avaialable to turn the wheel, my mileage should increase.
So my question for those of you who have put larger tires on your truck; did your mileage change?
Yes generally the bigger the tire the worse your mileage gets. Thats why most of the people here run programmers so you can add power safely,increase MPGs and adjust for your tire size.
__________________ They call me Butters
2002 CCSB Dmax
EFI Live, Straight piped 6" Black stacks, aFe intake, Z series autometer gauges, PPE Boost valve, Resonator blocked, Moto Metal 951s on 295/70 terra grapplers
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yeah, you have more weight with the larger tires. what your saying works in general but not with vehicle tires.
__________________ '06 Silverado 2500HD, lbz, CCSB, greystone color, 5" Magnaflow SS turbo back, Evo race lvl 5, blocked EGR, Cooper S/T on 09 stock wheel, S/C stage V w/1056, BD manifold, PPE lift pump and race valve in the box.
If your on the highway for long periods at a time I think the larger tires would be good for mileage. Getting the tires rolling is what takes more fuel. When I say larger I don't mean 40's.
__________________ 2003 GMC 2500HD- 4in. straight exhaust, intake, Suncoast Stage IV, Air Dog 150 lift pump, BD Supermax turbo, Isspro EV2 gauges, BD manifold, 6 in. RCD lift, EFI Live w/DSP 5 tuned by Xtreme FX Tuning.
No matter what the larger the tire the moer rollin resistance. Even on the highway there is more suface area for the wind to grab and drag on a larger tire. 33" tires and smaller will not make a huge difference. It seems that 35" seems to be the mark where the numbers start changein from my experience
__________________ Jordan Blake Tow Pig-03 LB7/Alli EX Cab Long Bed, Dually, alot of miles dents scratches and dents, EFI Alli-07 LBZ/Alli, Cognito, PPE, Airgdog, Bilstien, EFI McRat/Neens tuned, trippin auto meters, other things and stuff
The way it was explained to me was....
The tire is flat when it's on the bottom and round on the top. This flexing causes heat. Heat comes from the release of energy. So the flexing takes energy...
If the tire is wider it will take more energy because more area is flexing. That's why they say underinflated tires waste fuel.
I bet if you had tires with the same width, you would see better highway mileage than the stockers.
On my '05, I saw better mileage going from 245's to 285's, but it had 4.10 gears (gasser). On the '08 the lift and 35 x 13.50 wide tires killed the mileage. This truck has the 3.73 gears.
__________________ 2008 LTZ CrewCab Standard Box
Pace Edwards Full Metal JackRabbit cover
4" Putco Wheel to Wheel Stepbars
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20"x10" Ion Forged rims w/ 325/60/20 Nitto Terra Grapplers
Last edited by Toyaholic; 03-18-2009 at 07:28 PM.
Reason: added more BS
Way I look at it is....bigger tires make City mileage worse. But highway mileage should at least stay the same, or at worse drop maybe 1 MPG. But for the looks you get....it's worth it to me. I wish I could of done decent testing. When my truck was bone stock with 245's....I was getting 17.5 city and 20-21 Hwy...BUT...LSD was the only thing I could use...and it was GREAT. Then (no joke) as soon as I got my 265's put on and exhaust, the next day all the local stations switched to ULSD...and my mileage DROPPED. So I have no idea what my truck would of got using ULSD and 245's.
__________________ RIDE: 2007 Chevy CC LBZ / 6 speed LIFT: Ready Lift Leveling Kit STARTER: VIPER 2 Way w/Turbo Timer SOUND:Touchscreen Pioneer P4000DVD/Backup Camera - 6 1/2 Polk Audio everywhere else. ADD ONS: Cowl Hood, 6000K HIDs, Dominator II Steps, BFXenon Grill, ExTang Solid Fold, custom bug shield/vent shades TIRES/WHEELS: 305/70-17 Wrangler MTR Kevlar Tires on 17x9 Liquid Metal Gatlins AIRFLOW: BANKS Monster Dual Exhaust, EGR blocked & CAT removed with MBRP replacment pipe and BANKS Ram Air. PROGRAMMERS: BANKS 6 Gun PDA w/Speed Loader --STACKED-- with Quadzilla Stealth 2
Pretty much everyone here is correct, but as you lift your vehicle, Your aerodynamic wind force drag doubles as the tire size increase. Not only just because of friction that cause a decrease in mpg, its also the increase of height of the vehicle that causes more force against the wind or no wind. Think about it, why do nascar race vehicle has a very relatively low center of gravity? Because there is better handling and a dramatic increase in aerodynamic flow with the body than against the body to increase the efficiency of the vehicle. For every inch you increase, you can lose between 5 to 10% in fuel economy.
__________________ 06 LLY CCSB
Just another white truck on the site.
Tuned by Killerbee's Original LBZ tune.
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All things being equal a larger diameter tire will always require more force to rotate.
I'll elaborate further:
Tire/Wheel A: 50 lbs, 12" width, same tread, same brand, same air pressure, 33" diameter
Tire/Wheel B: 50lbs, 12" width, same tread, same brand, same air pressure, 31" diameter
Let's just assume Wheel A is an 18" rim and Wheel B is a 16" rim, but they both weigh the same.
Tire A WILL have worse fuel economy.
There is a simple physics explanation for this.
Does anyone care to do an experiment that will prove without a doubt a larger diameter tire - with all other things being equal - will require more force to turn and keep turning?
All you will need is a swivel stool....
By the way, it has nothing to do with road resistance.
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yea yea, I know it's a truck, and YES I want the same mpg as a Civic 
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