Hey all -
I am debating what tires to purchase for my Eclipse. Currently, I have
245/45R17 Kuhmos on the car. I was planning on just getting the same
tires, but I decided to compare the acceleration provided by the g-Force
tires since they are offered in a smaller size of 235/40R17.
What I found is that the smaller tire offered by BFG offers a pretty
significant advantage in acceleration of about 5%. This would seem to be
enough to justify getting the g-Forces.
So here are my calculations:
Notes:
(1) using dyno measured torque at wheels
peak torque = 190 ft-lbs @ 3000 RPMs
(2) using 1st gear
torque @ wheels = peak torque * 1st gear ratio * final ratio
= 190 * 3.083 * 3.8
= 2226 ft-lbs
(3) disregarding tire deformation since it should be similar on both tires
Kuhmos (245/45R17):
diameter = ((width * series) * 2) / 25.4 mm/in) + wheel size
= ((245 * .45 * 2) / 25.4) + 17
= 25.68 in
radius = dia / 2
= 12.84 in
= 1.07 ft
thrust = torque / radius
= 2226 / 1.07
= 2080 lbs
BFG g-Force (235/40R17):
diameter = 24.40 in
radius = 1.017 ft
thrust = 2189 lbs
Thrust difference = (2080 - 2189) / 2080 = 5.2 %
So are my calculations correct?
Brad
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Bradley Lamont
email: lamont@xnet.com
http://www.xnet.com/~lamont
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