Wi | Eddy in TN - 2/16/2012 07:45 I copying this formula and putting it in my truck file!!! Thanks!! Knew the cheap tires were too good to be true!!!
Not necessarily too cheap to be true. You have to weigh it out. Low pro 24.5s are lighter, and have slightly less rolling resistance. However the gain from those would be lost in engine speed maybe. Here are the formulas for calculating that.
336.1355/Tire Diameter*Rear Axle Ratio*Desired Speed= Engine RPM in Direct (1:1 ratio in transmission). If you have an overdrive transmission multiply the RPM in direct by the overdrive ratio. Most Eatons are around 0.73-0.75.
Here is an example assuming a 3.70 Rear end with tall 24.5s (11R24.5)
336.1355/43.86=7.66
7.66x3.70=28.34
28.34x65=1,842
1,842x0.74=1,363
You know that the Low-Pro's are 6% Shorter So apply that.
1,363x1.06=1,445
So you gain 82 Engine RPM. Only you will know what this might do for your fuel economy. For most farmers, it doesnt matter we never run enough miles.
If you want I could put all of the formulas into an excel spreadsheet. |
Size Difference in 24.5 Semi Tires?
