Really stupid question but I don't know
 

Hey guys,
I know you are going to think that this is stupid but I got a question for ya.

I want to use the analyzer on this site to see the difference if I jump from 2.73s to 3.73s. It asks for the tire diameter.
My tires are 245/50/16. What is the diameter of those tires? Does anyone know?

Thanks
Scott

Just measure the tire height... Use a yar stick up against the edge of the tire. That's the easiet way.

Brad

Here is the formula to figure tire diameter and what your's is:

On a 245/50/16 tire:

245 * .5 *2 / 25.4 = 9.64567 (this is tire width in mm * ratio of sidewall height to width *2 to account for a sidewall above and below the rim / 25.4 to convert mm into inches)

then add the rim size, so 9.64567 + 16 = 25.6457 inches is your tire diameter

MPG???
 

OK, now that I have that, I don't understand how you guys can say that the change in gas milage on the highway isn't that bad. To go from 2.73s to 3.73, and driving at about 75, my rpms will be about 500 higher. How is that not going to affect the gas mileage that much. I would think that it would be a big difference.

Thanks
scott

It's all a matter of perspective. If gas mileage is of greater concern to you than performance, than certainly it will be a big difference, but if you are more concerned with acceleration, 500 rpms @ 75 mph is nothing. Most people spend a lot more time accelerating from a stop than they do cruising @ 75 mph, so the faster acceleration is enjoyed more than the loss of fuel efficiency is a negative.

Get it?

Take care,
~Chris

Trade Offs
 

Scott:

You're looking at a few mpg difference in the two gear ratios for a huge acceleration difference and frankly, when a Mustang owner is that concerned about his gas mileage I would advise one of two things; either leave the car stock as gas mileage is a bigger concern than performance to you, or buy a beater for errands and commuting and save the 'Stang for weekends and fun stuff.

Bottom line is that in all aspects, increased performance costs something.

Cash for parts, shorter life-span of parts and lower gas mileage, harder ride, noiser car, whatever. There is no free lunch and going faster isn't free, either. Accept the trade-offs or stay stock and be happy with what you have.

You decide.