Quote:
Originally Posted by b00m
Okay, 60mph wont cut it for me.I need to run at least 65 to 75 and still get decent mileage.I should mention that it has a 14.0 detroit.Just talked to one of my mechanics and said it was a good set up.But i still want to hear more from others.
TY
This little formula might help you decide:
RPM at 60 MPH = Axle ratio X Tranny ratio X Tires revs
I guess this truck has a direct drive tranny, so the "Tranny ratio" (top gear) will be 1. Regular 22.5 tires do usually 495 revs/mi; while tall rubber (24.5) do 473 revs/mi. To find out the RPM at 65 or 70 you put in all the numbers in this formula and then divide the result by 60 and multiply by whatever speed you plan to run at.
Example: tires revs=495, direct drive (1 ratio), axle ratio-2.90. The engine RPM at 60 MPH will be: 2.90 X 1 X 495 = 1435. The engine RPM at 65 MPH will be: 1435 / 60 X 65 = 1555 RPM
If you play with various tire types, you can find which setup will produce the RPM that Detroit recommends for cruising on the highway.