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  1. #11

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    People who are saying they have an MPG drop but haven't programmed their speedo, keep in mind that your MPG drop from a larger tire will be exaggerated because your odometer runs from the same sensors as your speedometer and they will be off by the same amount. While a larger tire will lower your MPGs, not reprogramming your speedometer will make it seem like a larger effect because the larger tire also has a larger circumference and you will travel slightly farther for each rotation of the tire. That means your odometer will also report less miles than you are actually travelling when you try to calculate your MPG.

    2008 FORD F350. My new all-around truck.
    2001 Silverado Reg. Cab Not-So-Base -- SOLD
    2003 Avalanche Z71. No Cladding. Check out my Mod thread. - Crashed. Will be rebuilt soon.
    1974 Triumph Spitfire 1500 - Work in Progress
    2003 Sierra 3500 Duramax. The Newer, Better Work Truck -- FOR SALE


  2. #12

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    Quote Originally Posted by pmf608 View Post
    People who are saying they have an MPG drop but haven't programmed their speedo, keep in mind that your MPG drop from a larger tire will be exaggerated because your odometer runs from the same sensors as your speedometer and they will be off by the same amount. While a larger tire will lower your MPGs, not reprogramming your speedometer will make it seem like a larger effect because the larger tire also has a larger circumference and you will travel slightly farther for each rotation of the tire. That means your odometer will also report less miles than you are actually travelling when you try to calculate your MPG.
    This is a correct statement.^^^^^^^^

    My examples were with a corrected speedo as well.
    David
    2004 Silverado 2500 Crew Cab 4x4, AMSOIL EA air filter, Granatelli MAF sensor, Throttle body spacer, Magnaflow exhaust (true dual to 2 in 1 out muffler), 6" ProComp lift (add a leaf and 5" superlift rear block), Bilstein shocks, 35's (Cooper Disoverer ST) and 4.10 gears, Rhino Liner, EGRUSA fender Flares and widow visors, extended stainless steel brake lines, firestone airbags w/onboard air compressor, Pioneer Avic X940BT navigation, Accel backup camera.
    http://www.gmtruckclub.com/forum/sho...Silverado-2500
    1960 Land Rover Series II 88
    2001 Pontiac Sunfire
    2013 Toyota Avalon Limited (Wife's Car)
    NRA Life Member

  3. #13

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    I have a programmer in my truck... and swapping between stock and 33's changes my mpg an average of 2 mpg. Now just to do a difference in speed testing I had a friend follow running my stock tires when I had speedometer adjusted for the larger and speed difference was 3-5 mph at 45. I didnt test it the other way around as I just wanted to know the difference when I put my winters on and don't adjust the speedometer.
    2009 Chevy Silverado 2500HDLT 6.0L w/ Towing Package, Dick Cepek GM8 Rims, Dick Cepek FC II 33X11.50R17,RKSport Ram-Air Hood(Functional), Lazer Lite Aluminum Tonneau Cover, Road Armor Stealth Bumper, PIAA Lighting, Diablo Trinity Tuner, Diablew Custom Tune, BullyDog Cold Air Intake, American Racing Headers w/highflow cats, Corsa Performance Sport Exhaust, Custom Striping, Black Bowties front and rear, Fuel Grille Inserts, Recon Headlights, Readylift Shocks, Readylift Upper Contol Arms, 2" Blocks in the Rear..

    Future Plans: HD Tie Rods, Under hood upgrades, Crower Camshaft and possibly electric fans.

  4. #14

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    Tim, you only did a "one-up" size change, which has negligible impact on performance or economy. It is the max that is recommended by virtually all tire retailers. You got a better look, and it didn't affect much.

    - - - Updated - - -

    Aj,
    Your stock tire weighs about 39/40 pounds. The tire you will replace it with weighs 57 pounds! So, 17 pounds x4 is 68 additional pounds. Now, that doesn't sound like much, but it is "unsprung" weight, which is not at all like the same amount of weight being put into the back of the truck. Your truck will have to overcome more drag each time you accelerate. The diameter is about a 4% increase, which will likely make your speedometer run about 3 MPH lower than actual, and your odometer will be off by about 2 miles every 100. The speed and odometer errors can be corrected, but the mass/weight will always be there. You will love the way your truck looks, but you may not be too happy with the other changes.

  5. #15

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    Quote Originally Posted by buckmeister2 View Post
    Tim, you only did a "one-up" size change, which has negligible impact on performance or economy. It is the max that is recommended by virtually all tire retailers. You got a better look, and it didn't affect much.

    - - - Updated - - -

    Aj,
    Your stock tire weighs about 39/40 pounds. The tire you will replace it with weighs 57 pounds! So, 17 pounds x4 is 68 additional pounds. Now, that doesn't sound like much, but it is "unsprung" weight, which is not at all like the same amount of weight being put into the back of the truck. Your truck will have to overcome more drag each time you accelerate. The diameter is about a 4% increase, which will likely make your speedometer run about 3 MPH lower than actual, and your odometer will be off by about 2 miles every 100. The speed and odometer errors can be corrected, but the mass/weight will always be there. You will love the way your truck looks, but you may not be too happy with the other changes.
    I was just sharing my info for just going up 2" in tire size. That amounts to 2 - 3 miles per gallon amounts to almost 50 - 75 miles a tank... or roughly 3 or 4 gallons of gas. That is just with about $13.

  6. #16
    Jr. Mechanic
    Join Date
    Apr 2009
    Location
    North Dakota
    Posts
    130

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    You never stop paying for that oversize rubber. You just can't beat physics.
    2013 Escape Titanium 4WD

  7. #17

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    Quote Originally Posted by buckmeister2 View Post

    Aj,
    Your stock tire weighs about 39/40 pounds. The tire you will replace it with weighs 57 pounds! So, 17 pounds x4 is 68 additional pounds. Now, that doesn't sound like much, but it is "unsprung" weight, which is not at all like the same amount of weight being put into the back of the truck. Your truck will have to overcome more drag each time you accelerate.
    assuming we are talking bout tires of the same width here and tires of the same height, which for time saving purposes, lets say so....
    the 68 additional pounds from a tire of exactly the same size, is EXACTLY the same as 68 additional pounds distributed onto your truck, I get what some people say about this being rotational weight vs. static weight, but realize this, since the tires sit on the ground on a vehicle, if tire size hasnt changed, but weight has increased, then you will have the exact same effect from 68 additional pounds in rubber weight on your rims as you would from static weight in your bed. The only time acceleration, stopping distance, rwhp, etc. changes is when the tire width and/or tire height changes, not weight, unless it is an absurd amount.

    it really is just physics, something ive had too much of in the last few years LOL
    Last edited by reggiecab2000; 05-15-2013 at 10:19 PM.
    2000 Chevrolet Silverado

    Powertrain:
    4.3L V6, 4L60E, 2WD, Single Cab
    Performance:
    Airaid CAI
    Poweraid TB Spacer
    Flowmaster 10-series exhaust (dumped)
    BLACKBEAR TUNED!!!
    Edge CS insight monitor
    4.10 gears
    Limited-slip differential
    LS-1 Dual Electric fans
    Corvette tranny servo swap

    Audio:
    Head Unit: Alpine
    Speakers: Alpine SPR-60C 6.5" component set, 4X6 Infinity Kappas
    Subs: 2-12" Kicker CVT's
    Amps: Alpine-M1000 (subs), Alpine MRX-F65 (Speakers)


    Tires/Wheels:
    305/70R16 NITTO Terra Grapplers
    16" PROCOMP 7089's
    Suspension:
    2" leveling kit
    3" Fabtech Spindle Lift Kit
    Front/Rear-Bilstein 5100 shocks

    Lighting:
    FRONT
    35W HID Low Beams
    RECON LED smoked roof cab lights
    REAR
    HELLA LED taillights and 3rd brakelight
    HELLA FF-75 Aux. Reverse Lamps
    RIGID dually D2, flush mount, wide beam
    Accessories:
    Hawk HPS Brake pads
    Russell braided steel brake lines
    Powerstop-red powdercoated brake calipers
    Powerslot Cryo brake rotors
    EGR in-channel window visors

  8. #18
    Jr. Mechanic GrizzlyTN's Avatar
    Join Date
    Jun 2010
    Location
    Jackson Tennessee
    Posts
    130

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    I don't have a bunch of math and stats but I can recommend the Toyo Open Country MT's it's more a cross with an AT and the quietist MT I've ever rolled on. I had Nitto Mud Grapplers and they looked great and cut mud like a pro but they were loud as two coons screwin. Yes Toyo's cost more but if you're trying to get the "tough" look and mud capability without the road noise these are what you want.
    2012 Chevy Silverado Z71 4x4 5.3
    Rough Country 2.5' Lift/Level
    Chevy 18's on Toyo Open Country MT 33's
    DiabloSport Trinity Tuner with Custom Tune from Lew
    Debating on AMP Research Powersteps

    2008 GMC Sierra WT 4x2 4.3

    3" Rough Country Suspension Lift w/Control Arms
    Super 44 Flowmaster Straight Dual Exhaust from the Cat Back with 18" Chrome 3.5" Exhaust Tips.
    Moto Wheels 951 18" on Nitto Mud Grappler 33's
    Infinity Kappa Perfect 6.1 System with Kenwood 5.1 amp using Stock Headunit.

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