S
Sierra SnowTurtle
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Perhaps the answer to why larger tires appear to get lower gas mileage. This is not a proof but just a theory.
My 2004 Rav4 4x4 tire size: Factory 235/65/16
235mm x .65 ratio =152.75mm ~ 6.01in (sidewall height)
6.01in X 2 + 16in = 28.02in (tire height)
Circumference = 28.02in*Pi = 88.02in. (distance per rotation)
Larger tire: BFG A/T 235/70/16
235mm x .70 = 164.5mm~6.47in (sidewall height)
6.47in X 2 + 16in = 28.95in (tire height)
Circumference = 28.95in*Pi = 90.95in. (distance per rotation)
For the sake of this theory I’m assuming 21 Miles per gallon.
21 miles ~ 1330560 in
To cover 21 miles:
1330560in/88.02inches per rotation =
15116.5644 rotations of my 235/65/16 factory tire
Or
1330560in/90.95in per rotation =
14629.5766 rotations of a Larger 235/70/16 BFG tire.
The odometer is calibrated to factory size tire so regardless of the tire size, the computer recognizes one rotation of the wheel as 88.02 inches traveled.
14629.5766 rotations of larger tire * 88.02in = 1287695.3403in ~ 20.323 mile
So the 21 miles traveled on the larger diameter tire will only show up as 20.323 miles on the odometer, a difference of .677 miles per gallon or 8.124 miles over 12 gallons (roughly the size of the tank). Therefore unless the odometer is recalibrated after switching to larger sized tires the distance traveled will appear less than it really is.
Again, just a theory.
My 2004 Rav4 4x4 tire size: Factory 235/65/16
235mm x .65 ratio =152.75mm ~ 6.01in (sidewall height)
6.01in X 2 + 16in = 28.02in (tire height)
Circumference = 28.02in*Pi = 88.02in. (distance per rotation)
Larger tire: BFG A/T 235/70/16
235mm x .70 = 164.5mm~6.47in (sidewall height)
6.47in X 2 + 16in = 28.95in (tire height)
Circumference = 28.95in*Pi = 90.95in. (distance per rotation)
For the sake of this theory I’m assuming 21 Miles per gallon.
21 miles ~ 1330560 in
To cover 21 miles:
1330560in/88.02inches per rotation =
15116.5644 rotations of my 235/65/16 factory tire
Or
1330560in/90.95in per rotation =
14629.5766 rotations of a Larger 235/70/16 BFG tire.
The odometer is calibrated to factory size tire so regardless of the tire size, the computer recognizes one rotation of the wheel as 88.02 inches traveled.
14629.5766 rotations of larger tire * 88.02in = 1287695.3403in ~ 20.323 mile
So the 21 miles traveled on the larger diameter tire will only show up as 20.323 miles on the odometer, a difference of .677 miles per gallon or 8.124 miles over 12 gallons (roughly the size of the tank). Therefore unless the odometer is recalibrated after switching to larger sized tires the distance traveled will appear less than it really is.
Again, just a theory.