Tire Size Change

[fireman32_14]

how much power would i lose going from a cooper p265/70/17 with a 31.4 inch diamater to a firestone destination LT275/70/17 with a 32.2 inch diamater?

[svensk]

You would lose a slightly noticeable amount. I would rather drop a size to a 255 imo. I have 265's and lost some power from the 245 stock even though the 265's look more manly.

Do you really like the look of the 275 better? I personally would rather have the performance.

[VMax2007]

On my 2000 GMC Sierra Z71 Ext cab 5.3, I went from stock 265's to 285's and I never noticed any difference, based on the "Butt-Dyno" anyway. But I never raced with it either. Mileage didn't change noticeably either and my speedo was only off by about 2-3 MPH at 70MPH.

[Zembonez]

how much power would i lose going from a cooper p265/70/17 with a 31.4 inch diamater to a firestone destination LT275/70/17 with a 32.2 inch diamater?

Very little real difference in size (percentage wise) should equal very little difference in power.

 

I HIGHLY recommend the Firestones. I have a set of Destination ATs on my Jeep Cherokee and just put a set of Destination LEs on my dad's Suburban. Man, what a difference they made in both trucks. Never been a big Firestone fan but they are awesome. Smooth and quiet too. I'm very pleased.

[2004GMC1500CC]

how much power would i lose going from a cooper p265/70/17 with a 31.4 inch diamater to a firestone destination LT275/70/17 with a 32.2 inch diamater?

None that you would ever notice.

[SinisterSS]

The laws of physics say 2.5% less power.

[VMax2007]

The laws of physics say 2.5% less power.

 

True, but when you factor in all of the other variables, such as temp, humidity, elevation, gas content, weight, etc. Your net power varies more than that on any given day anyway.

[Zembonez]

The laws of physics say 2.5% less power.

Not true. Dimensions say 2.54777% difference in diameter. Diameter does not equal power.

 

Power calculation is complicated as is application of applied torque. Barometric pressure, temperature, fuel octane, beer temperature... Many factors including torque curves, new versus old tire rolling resistance and weight, cost of plutonium on Mars, amount of air pressure in Wingnut's left rear tire, etc... enter into the equation.

 

I think we will have to get a scientist involved. Hand me another beer.

[2004GMC1500CC]

The laws of physics say 2.5% less power.

Not true. Dimensions say 2.54777% difference in diameter. Diameter does not equal power.

 

Power calculation is complicated as is application of applied torque. Barometric pressure, temperature, fuel octane, beer temperature... Many factors including torque curves, new versus old tire rolling resistance and weight, cost of plutonium on Mars, amount of air pressure in Wingnut's left rear tire, etc... enter into the equation.

 

I think we will have to get a scientist involved. Hand me another beer.

 

and since you very rarely (if ever) use all of the power available (don't forget about torque management), any power it MAY rob will (again) never be noticeable. I'm not a scientist, but I am an Engineer, does that count?

[VMax2007]

and since you very rarely (if ever) use all of the power available (don't forget about torque management), any power it MAY rob will (again) never be noticeable. I'm not a scientist, but I am an Engineer, does that count?

 

 

d**n Engineers....oh, wait, nevermind.

[svensk]

You have to factor in the increased weight of the larger tire along with the slightly wider diameter

[stillen]

I'd like to chime in, and I don't want to get specific, only maybe offer my test results when i went from 265's to 285's...

 

There is only a difference of 1.2 inches in diameter from 265's to 285's (70 series). BUT that's diameter, Since you are only really riding on the radius you are only higher 1/2 inch. I did NOT notice any difference, and both my tire sizes were BFG M/t's

 

To compare, I run 31's on my jeep, They were 31's when i bought the tires brand new, Again BFG M/T's, When they had just over 10k miles on then, I remeasured the diameter, and it was close to running 29's maybe closer to 30's. Here I did NOT notice a difference either.

 

The tire calculators you find on google and such are good for new tires i think. You can do the tire comparison and all, but it doesn't take in consideration of overinflation / underinflation, or how many times a brake stand has been done.

[SinisterSS]

The radius of a tire is a simple lever when it comes to its affect on power. Do the math.

 

As for temperature, atmospheric pressure, etc. - of course they affect power output so let's call that a constant when comparing just tire A to tire B.

[Zembonez]

The radius of a tire is a simple lever when it comes to its affect on power. Do the math.

 

As for temperature, atmospheric pressure, etc. - of course they affect power output so let's call that a constant when comparing just tire A to tire B.

This is getting fun!

 

In case nobody noticed, my last post was not intended to be taken seriously.

[Zembonez]

The laws of physics say 2.5% less power.

Not true. Dimensions say 2.54777% difference in diameter. Diameter does not equal power.

 

Power calculation is complicated as is application of applied torque. Barometric pressure, temperature, fuel octane, beer temperature... Many factors including torque curves, new versus old tire rolling resistance and weight, cost of plutonium on Mars, amount of air pressure in Wingnut's left rear tire, etc... enter into the equation.

 

I think we will have to get a scientist involved. Hand me another beer.

 

and since you very rarely (if ever) use all of the power available (don't forget about torque management), any power it MAY rob will (again) never be noticeable. I'm not a scientist, but I am an Engineer, does that count?

 

YOU may be an engineer but you are from Texas... You are forgiven!!!