tire size input

When programming the ECM it should ask for top gear ratio, rear end ratio, and tire size. This will translate into pulses per mile. Pulses per mile will tell the ECM how fast the truck is moving.

 

it dose ask for rev. per mile on tires. 11r24.5 is 476. i have the other sizes in my truck and it's not here rt now. i will check later. check roadranger's web site under calculator gives tire size top gear rear end ratio and find out how fast your truck ant. you also can do RPM X 60 devided by top gear ratio devided by rear end ratio devided by tire REV per mile will give you road speed in miles per hour. so when your buddy say's his 18sp with 3.55's will run 120 mph, he better be able to turn 2500 RPM's

 

Why not go to the source. The tire manufacturers all have their specs online.

 

tire manufacturers give specs for a new tire, they are about 473 rev per mile when you spec a new truck the computer they use give 476 as an average between new and somewhere before worn out.

 

For the pulses per mile setting in the ecm, I think I remember that they take tire revs times a multiplier. The mfr. dealer can tell you what the multiplier is for your drive gear and trans.

 

4.30 ratio x 16 teeth on rear output x 476 tire revs = 32749 ppm on a Cat ECM.