Quote:
Originally Posted by mcrews
Since 245 is the stock factory tire and 255 the tire I run.....oh and you can read any of my posts and see that I only refer to the advantage of ther one size up tire EVERY time as a key reason for my mpg.
AND I have used a Garmin 360 Nuvi to acuratly calculate my miles on long trips to ACCURATELY document the REAL miles and TRUE MPG
BUT here is the chart from TIRERACK.com on the Kumho's that I run.....
size 245/45ZR18 255/45/18
max psi 50 psi 51psi
tread depth 11/32" 10/32
weight 30lbs. 30lbs
rims 7.5-9" 8-9.5
overall width 9.6" 10.1
tread width 9" 9.3
diameter 26.7" 27”
rev per mile 778 769
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255/45R18
Section Width: 10.03 in 255 mm
Rim Diameter: 18 in 457.2 mm
Rim Width Range: 8 - 9.5 in
Overall Diameter: 27.03 in 686.56 mm
Sidewall Height: 4.51 in 114.55 mm
Radius: 13.51 in 343.15 mm
Circumference: 84.91 in 2156.7 mm
Revs per Mile: 769.5
Speedometer Difference: 1.312% too slow
Diameter Difference: 1.3%
same basic demensions would you say?
Heres the thing, I may not know everything about tires, but i do know math. You save 10 revolutions per mile, which is:
84.91 inches x 10 revolutions=849.1 inches per mile.
you have what? an 18 gallon tank, at your advertised average of 27mpg you are getting roughly 486 miles from one complete fill-up.
849.1 inches x 486 miles=41,2662.6 inches.
there are 63,360 inches in a mile, which means your getting less than one free mile per fill-up. if you can tell a difference its not from your tires, atleast not from a height stand point.
why would he someone spend 3-400 or more dollars on new tires that make little to no difference? If the tires were still good, Id much rather experiment with a set of 4 $80 springs i bought at a local PYP.
and it wasnt the concept of active suspension, it was that manufacturers use active suspensions that "lower" the car at highway speed thereby decreasing drag. Lowering a car is on the list of mods here at ecomodder and is listed almost everywhere else as a drag decreaser with some limitations. So why would someone not try lowering it? other people have lowered their cars in this thread with semi-ok results.
Quote:
Originally Posted by mcrews
Again, why lower it. REALLY. why? I can tell you from firsat hand experience there is no noticable difference in mpg w/ lowering.
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Your basing your knowledge on the lowering issues on first hand experience. When you changed your springs, did you do any other modifications to your suspension when you swapped them out?