Hi Duke:
I have been doing the same calculation but for a different reason: I want
less sturm & drang from the engine room, not just better fuel economy.
Spending 17 hours at highway speeds with the"racket" reduced is a big
incentive for me.
I have driven to Midcoast, Maine the last two years to the annual "Tiger"
gathering at the Owl's Head Museum and both times got approx 25 miles to the
Canadian gal. (~21 miles/U.S. gal.) for the 1500 mile return trip.
http://www.engineeringtoolbox.com/fuel-consumption-converter-d_850.html
My car also has a 3:09 rear end, but I am running 205x50Rx15 rear tires
(23.07" dia) 901.6 revs/mile. Absolutely no clearance problems on stock,
unmodified rear wheel arches.
But I think you should consider a different size - try 195x70x13. Should fit
no problem, and you get 876 revs/mile, a significant difference: 6.45%.
Here's a great calculator to make this comparison easy:
http://www.1010tires.com/TireSizeCalculator.asp?action=submit&reset=yes
Only problem is, tire manufacturers recommend you don't change tire size
more than 3% for fear of the risk of brake failure. I have no idea how great
this danger might be, but I am running Wilwoods and vented discs up front,
with stock brakes in the rear, so I'm not too concerned. Do you have
upgraded brakes?
Dave
One way or another - see you there....
Subject: [Tigers] Gas milage with different tires?
> 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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