Well I think you would come up a bit short. No math wiz here but I'll try
based on your claimed rev numbers your effficency would improve by .9775 %.
You dont include your current MPG at 78Mph but assuming you now get 20MPG you
would improve to about 20.2MPG. in a 1600 mile trip you would use 80 gallons.
With the $170 tire purchase you'd cut that to 79.2 Gallons. At $3 gallon you'd
save less than $3. If your current MPG is better than 20 your savings would be
even less.
Maybe someone will show I made a mistake
--- On Sat, 7/3/10, wsamouce <wsamouce@kc.rr.com> wrote:
From: wsamouce <wsamouce@kc.rr.com>
Subject: [Tigers] Gas milage with different tires?
To: tigers@autox.team.net
Date: Saturday, July 3, 2010, 8:49 PM
Hey guys,
I am thinking about a bigger rear tire to save me some $$ when driving 1600
miles to TE/AE United 2010. The Sumitomo's I have (195/60R13) are 22.4 in
diameter and 935 revs per mile. If I go to the 205/60R13, they are 22.8 in
diameter and 914 revs per mile. I am trying to figure out if the gas
savings would offset the $170 cost of the tires with mounting.
I just can't get my head around the math to figure it out. I am currently
running 3600 RPM at 78 MPH (3.07 gear). I plan on running the same speed,
with cruise control, all the way to Maine. The larger tire would allow me
to run at 3535 RPM for the same speed.
TIA!
Duke
B382002037
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