Originally Posted by ubengineer
Can someone please let me know your setup regarding tire size vs gears and what rpms are you getting on the highway.
Let's say you went from 3.23's to 4.56's. Your engine has to turn the driveshaft more to maintain a given speed going down the road. In this example your drive shaft has to turn 1.23 more times before the ring gear makes one revolution. 4.56 - 3.23 = 1.23
Off road drivers want to rpm low and not stall. They go tall tires for clearance and very 'tall' gears. They may also alter the xfer case ratio to help them do that even more.
Drag racers can 'run out of engine' before they get through the 1/4 mile if they gear too high. In a perfect world they want to run out of engine just as they pass through the lights.
How does this weekend warrior get his rig to the drags if it is geared too high and he has no budget for a ramp truck? A set of real tall street tires.
I run stock 3.07's in a '95YJ 4.0 automatic. I went with 31" tires which are ~10% larger over stock tires. So my speedo says I am doing ~ 60 when in fact I am doing more like 65. The distance travelled and speed I am driving in my YJ is measured at the T-case......before the taller than stock tires.