Really stupid question but I don't know

SCOTTLT79 · 07-24-2002, 02:51 PM

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

Coupe Devil · 07-24-2002, 02:59 PM

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

Brad

Hethj7 · 07-24-2002, 03:00 PM

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

SCOTTLT79 · 07-24-2002, 03:09 PM

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

PKRWUD · 07-24-2002, 05:20 PM

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

Mr 5 0 · 07-25-2002, 12:27 PM

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.

07-24-2002, 02:51 PM	#1
SCOTTLT79 Registered Member Join Date: Aug 2000 Location: Raynham, Ma, USA Posts: 189	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 __________________ 95 Red Mustang GT Pro 5.0, MAC fenderwall cold air induction kit, BBK Off-Road H-pipe with Magnaflow cat-back system Mostly stock(looking to modify) Rice Haters Club Member #63

07-24-2002, 02:59 PM	#2
Coupe Devil Moderator Join Date: Mar 2001 Location: Myrtle Beach SC Posts: 1,643	Just measure the tire height... Use a yar stick up against the edge of the tire. That's the easiet way. Brad __________________ 1990 GT, 347, TFS TW Heads, TFS Cam, TFS Track heat, Twin turbos, FMIC, T5. Built Ford Tough Moderator

07-24-2002, 03:00 PM	#3
Hethj7 Mizzou Tigers Join Date: Apr 1999 Location: weston, MO United States Posts: 1,455	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 __________________ 2006 Mustang GT 1990 LX GT-40 motor 262 horsepower, 307ft-lbs (sold but forever loved) 1998 Contour SVT Rice Haters Club Member #244

07-24-2002, 03:09 PM	#4
SCOTTLT79 Registered Member Join Date: Aug 2000 Location: Raynham, Ma, USA Posts: 189	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 __________________ 95 Red Mustang GT Pro 5.0, MAC fenderwall cold air induction kit, BBK Off-Road H-pipe with Magnaflow cat-back system Mostly stock(looking to modify) Rice Haters Club Member #63

07-24-2002, 05:20 PM	#5
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	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 __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

07-25-2002, 12:27 PM	#6
Mr 5 0 Conservative Individualist Join Date: May 1997 Location: Wherever I need to be Posts: 7,487	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.

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