Confused again about rear end ratio

No no! Your IFTA is based on gallons consumed. Your miles in each state ÷ your overall MPG for the quarter = per gallon rate of IFTA owed (minus what was paid at the pump).
Now your overall MPG for the quarter will be higher if your odometer shows more than actual miles traveled and vice versa but the gallons used figures out to the same number.

Example:

State A you ran 1000 actual miles.

In actuality your real MPG was 5 because you burned 200 gallons.

If your odometer was rolling on 20% more miles than actual, you would show 1200 miles. You still burned 200 gallons but now the MPG is 6 due to the inaccurate odometer.

If your odometer was rolling on 20% less miles than actual, you would show 800 miles. You still burned 200 gallons but now the MPG is 4 due to the inaccurate odometer.

State A's IFTA per gallon is $.20

In actuality you would owe $40 (1000 ÷ 5 = 200 x .2 = 40)
In the too many miles example you would owe $40 (1200 ÷ 6 = 200 x .2 = 40)
In the too few miles example you would owe $40 (800 ÷ 4 = 200 x .2 = 40)

 

No, the 255's are only good for ~10K per dual. The 275/70R22.5 we use on the steer are load range J, good for ~13.8K on the steer.

 

Here is the tire calculation that I use:

MPH=(RPM*60)/(TIRE RPM*GEAR RATIO*TRANS)

Where:
RPM=Eng RPM
Tire RPM=Loaded tire RPM from the tire manufacturer
Gear Ratio=Rear end ratio
Trans=Final transmission ratio

Generic tire RPM for the common tire sizes:

[TABLE="class: MsoNormalTable, width: 96"]
[TR]
[TD="width: 64"] TIRE SIZE[/TD]
[TD="width: 64"]

TIRE RPM​

[/TD]
[/TR]
[TR]
[TD="width: 64"]

LP22.5​

[/TD]
[TD="width: 64"]

512​

[/TD]
[/TR]
[TR]
[TD="width: 64"]

11R22.5​

[/TD]
[TD="width: 64"]

496​

[/TD]
[/TR]
[TR]
[TD="width: 64"]

LP24.5​

[/TD]
[TD="width: 64"]

496​

[/TD]
[/TR]
[TR]
[TD="width: 64"]

11R24.5​

[/TD]
[TD="width: 64"]

473​

[/TD]
[/TR]
[/TABLE]

Final Transmission Ratios:

[TABLE="class: MsoNormalTable, width: 96, align: left"]
[TR]
[TD="width: 64"]

Trans​

[/TD]
[TD="width: 64"]

Ratio​

[/TD]
[/TR]
[TR]
[TD="width: 64"]

10​

[/TD]
[TD="width: 64"]

0.74​

[/TD]
[/TR]
[TR]
[TD="width: 64"]

13​

[/TD]
[TD="width: 64"]

0.73​

[/TD]
[/TR]
[TR]
[TD="width: 64"]

18​

[/TD]
[TD="width: 64"]

0.73​

[/TD]
[/TR]
[/TABLE]






I would buy the lowest rolling resistance tires that I could afford and drive slow. I would think that your right foot would have more of a factor in fuel mileage than gearing??