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3,514 Posts

a mile or 2 i went to 265s and nothing changed

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284 Posts

Easier to spend it all at one time, at my house anyway.

Congrats on the new sled, you will love the Dmax,

SS

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16,971 Posts

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416 Posts

Be sure you remember that 245-285 is almost 8% different, so either recallibrate or rememeber to add 8% back onto your MPG calculation.

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3,514 Posts

yeah you can but like the guy said without a little lift you will rub

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460 Posts

:grd: -:t SWAP YOUR TIRES!!! Stockers are worthless!!

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4,101 Posts

The amount of milage you gain will depend on the size of increase, and will be a percentage figure, not a number of MPG. (A MPG figure can be calculated from your current MPG, but you can't say accross the board going from one size to another will add or lose a set number of MPG).

For example, a 245/70R16 tire has a diameter of 29.503937007874015 inches. If you upgraded to a 285/75R16 tire, that diameter will be 32.830708661417326 inches. [(32.8*100)/29.5]-100 will give you your percentage difference in diameter (circumference is a direct dependant of diameter). In this case, the increase is 11.2%. You'd get 11.2% better gas milage.

Another way of looking at it is this; a 245/70R16 tire has a diameter of 29.503937007874015 inches. If you upgraded to a 285/75R16 tire, that diameter will be 32.830708661417326 inches. A 29.5" diameter tire has a circumference of 29.5x[3.142 (pi)], or 92.7". A 32.8" diameter tire has a circumference of 32.8x[3.142 (pi)], or 103.1".

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5,839 Posts

it alllll depends on your right foot....

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1,035 Posts

No its not. Only D*dge builds a quad cab. If your back doors open with the front ones closed it is a crew cab. If they don't it is an extended cab. Otherwise...... :welcome: to the diesel place.beeler311;1602060; said:New here guys. I'm picking up my '07 Duramax tomorrow. It's a GMC quad cab reg bed.

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1,895 Posts

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98 Posts

When you do figure out your mileage, make sure you add about 5% on your miles driven. I followed my truck with 285's the other day with cruise @100 km and my radar showed it at exactly 105.. So that means speedo is out 5%..

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6,361 Posts

Yea and they look like little pizzasdundeediesel;1604438; said::grd: -:t SWAP YOUR TIRES!!! Stockers are worthless!!

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4,101 Posts

You have radar in your truck ?silverbirch04;1605628; said:When you do figure out your mileage, make sure you add about 5% on your miles driven. I followed my truck with 285's the other day with cruise @100 km and my radar showed it at exactly 105.. So that means speedo is out 5%..

Well, whatever you want to call it, quad, crew, 4 dr, etc.boondokr;1605412; said:No its not. Only D*dge builds a quad cab. If your back doors open with the front ones closed it is a crew cab. If they don't it is an extended cab. Otherwise...... :welcome: to the diesel place.

Um, not exactly. A larger tire with the same ID will weigh more than a smaller tire. There is more tq required to turn that the larger tire which uses more fuel. Yes, you will move farther with a single revolution, but you will use more fuel doing so. You can't simply say that since it is larger you will gain MPG.schulte;1604480; said:

The amount of milage you gain will depend on the size of increase, and will be a percentage figure, not a number of MPG. (A MPG figure can be calculated from your current MPG, but you can't say accross the board going from one size to another will add or lose a set number of MPG).

For example, a 245/70R16 tire has a diameter of 29.503937007874015 inches. If you upgraded to a 285/75R16 tire, that diameter will be 32.830708661417326 inches. [(32.8*100)/29.5]-100 will give you your percentage difference in diameter (circumference is a direct dependant of diameter). In this case, the increase is 11.2%. You'd get 11.2% better gas milage.To use this equation, you have to know the old and new diameter. [New Diameter] x 100 devided by [Old Diameter] all minus 100 will give you the size differential percentage.. The percentage difference in size will also be the percentage change in your milage. A good tire diameter calculator can be found here: http://www.americanracing.com/techcenter/DiameterCalculator/DiameterCalculator.htm

Another way of looking at it is this; a 245/70R16 tire has a diameter of 29.503937007874015 inches. If you upgraded to a 285/75R16 tire, that diameter will be 32.830708661417326 inches. A 29.5" diameter tire has a circumference of 29.5x[3.142 (pi)], or 92.7". A 32.8" diameter tire has a circumference of 32.8x[3.142 (pi)], or 103.1".In other words, a 285/70 tire will move you 10.4" more forwards than a 245/70 tire will, upon each revolution.

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266 Posts

Don't forget that the tire is wider as well. This usually effects MPG negatively.

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4,101 Posts

This's true, the equation is not 100% accurate and does not take into account all the factors.beeler311;1606003; said:Um, not exactly. A larger tire with the same ID will weigh more than a smaller tire. There is more tq required to turn that the larger tire which uses more fuel. Yes, you will move farther with a single revolution, but you will use more fuel doing so. You can't simply say that since it is larger you will gain MPG.

More torque is required to turn a larger tire, but this simply results in a change in where your truck is most efficient. Smaller diameter tires are more efficient during accelleration, and larger diameter tires are more efficient at a constant speed, because less RPM's are required to achieve the same distance traveled forwards. Becuase most of the time you spend driving you're NOT accellerating, larger tires (within reason), will give you better milage.

This's even more the case when the motor in question is a diesel; lower engine RPM's requiring higher torque are favorable over higher RPM's requiring lower torque, due to the torque curve for a diesel engine. Basically, you're usually cruising at a higher RPM than the peak torque RPM, meaning any closer you get to the peak torque RPM, the less fuel you'll use covering the same distance.

This's true. The equation I provided is not 100% accurate, but it WILL give a rough estimation of the change in fuel economy in relation to a change in tire diameter.beeler311;1606003; said:You can't simply say that since it is larger you will gain MPG.

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