Ok, Diana, Nico, and Karl, thanks so much. A lot of what you all said was close to some of what I thought, but you defined it for me.
I will use your info to try to solve our problem, and for now just slow down. Lost 5+ mpg, which to me is a lot, for the cookie jar has no funds for stock. If others reply to help, it will be tomorrow before I get back to mail. Last load of laundry calls to be put away, then this tired lady must go to sleep before another work day starts:) Mimi Sent from my iPhone On Jul 31, 2012, at 11:42 PM, Diana Tomchick <diana.tomch...@utsouthwestern.edu> wrote: > Mimi, > > A simple back-of-the-envelope calculation would be to divide the current tire > circumference by the previous tire circumference. This would give you an > estimate of the fractional difference the new, larger tire would travel for > each revolution of the tire. Using the numbers you supplied gives a value of > approximately 1.071. If you are used to driving at 60 m.p.h., in theory the > new tires would actually be taking you at 60 x 1.071 = 64.26 m.p.h. > > Of course this is a pretty simplistic estimate. > > If you want to maximize your gas mileage, that's a more complicated > experiment that would need you to fill your gas tank (be sure to always use > the same type of gas--the higher the percentage of ethanol, the lower your > mile per gallon), drive a set distance at different speeds and re-fill the > tank to see how much you used. Oh, and be sure that the prevailing wind speed > and direction is the same every time you repeat the drive at the different > speeds. > > > Diana > > ******************************************************** > Diana R. Tomchick > Professor > Dept. of Biochemistry > University of Texas Southwestern Medical Center > 5323 Harry Hines Blvd. > Dallas, TX 75390-8816 > (214) 645-6383 (office) > (214) 418-5827 (cell) > diana.tomch...@utsouthwestern.edu > > On Jul 31, 2012, at 11:09 PM, "Mimi Jasek" <mjca...@gmail.com> wrote: > >> Ok, I need help. I have a Ford Escape that we use as our main caving vehicle >> due to great gas mileage. Due to age, miles, and need for stronger sidewalls >> and better traction, we traded our old tires for new. Love them, but because >> bigger, noticed huge drop in gas mileage at same speeds used to traveling, >> and I seem to be staying up with or passing everyone!! >> >> Old = P235/70R16 normal street tires >> >> New = LT245/75R16 E Toyo OPAT OWL 120Q >> >> Don't want a speeding ticket, and need my good mpg back, or close to it. Can >> anyone tell me how much to decrease my speed, and if the reduction is the >> same for all speeds? If not the same, how much decrease at what increments? >> >> I believe my old tires were 28" diameter (spare is that) with 7.33' >> circumference, and new are 30" with 7.85' circumference. >> >> I have to believe there are more than enough math wiz/ tire savvy folks out >> there to get me some answers, but if I am asking the impossible, tell me. I >> do have a tachometer as well as a speedometer if that helps. >> >> For us, mpg means a lot due to cost of gas, and determines how many trips we >> make. I would really appreciate any help anyone can give me. >> >> Thanks, >> >> Mimi Jasek >> >> >> >> Sent from my iPhone >> --------------------------------------------------------------------- >> Visit our website: http://texascavers.com >> To unsubscribe, e-mail: texascavers-unsubscr...@texascavers.com >> For additional commands, e-mail: texascavers-h...@texascavers.com >> > > ________________________________ > > UT Southwestern Medical Center > The future of medicine, today. --------------------------------------------------------------------- Visit our website: http://texascavers.com To unsubscribe, e-mail: texascavers-unsubscr...@texascavers.com For additional commands, e-mail: texascavers-h...@texascavers.com
