Odometer difference from 24.5 to 22.5 wheels

Going from 24.5 to 22.5 will require a gear change to keep things the same.

Don't bother with the long drive, you can figure it all out with a calculator.

Google "tire size calculators" related to the sizes you want.

So, if switching to a smaller tire will raise the rpm's at the same speed then the odometer will read more miles than actual and the speedo will read faster than actual.... I think I have that right, right??

Curious as to where the ECM and ODO pick up there mileage readings.

 

Those two numbers will always be different. The ECM uses the GPS system of the truck, and the Odometer uses the number of rotations of the tire. The GPS is considered more accurate. Those numbers are 10% different, I have read when they get 18% or greater apart the numbers should be reset to agree. I do not think the tire size makes much of a difference, super singles usually have an aspect ration of about 50% and standard truck tires have usually an aspect ratio of 88% (aspect ratio is the ratio of the height/width of the tire), the bigger the aspect ratio the bigger the tires sidewalls will be, but since super singles are twice as wide, that means the sidewalls are taller for the super single, so bottom line the circumference of the 22.5 super singles should be about the same as the 24.5 doubles, so the tires should not be making much of a difference on the odometer reading. BTW, if your odometer reading is wrong than your speedometer reading will also be wrong. If you can find the tire size of the old tires and new tires (not just the radius), you can use an online calculator to determine the % difference in mileage --- but I am betting they will be near identical.

 

Dividing the circumference of one tire into the circumference of the other will give the percentage. Simple math.

 

Both readings should come from the output of the transmission, unless the body computer takes it's reading from the ABS sensors. Most I have dealt with in the past had either a single sensor on the back of the trans, with the ODO computer picking up the mileage that the ECM broadcasts on the J1939/J1587, or with a separate sensor for the ECM and the dash.

 

Not sure about a 2007 Freightshaker but check the back of the speedo. My 1998 KW has dip switches.

 

I'm guessing at some point there was a dash issue that caused the odometer/speedometer to quit. Because they get their input from the same source, and on a 2007 model, I believe ECM reads the speed sensor and outputs a signal for the speedo. something as simple as a blown fuse could have been the cause.

 

Simple math= language translated to the task; length of the perimeter will be calculated by inches. Then, showing the perimeters length for 24.5 Vs. 22.5 tire size. Myself, i would like to know the total of the tire rotations required to travel a mile distance involved for each product. Tire size used was a 275/80 changing from 24.5 vs. 22.5: (24.5=482.5 rotations per mile, 22.5=506.7 rotations per mile.)
i believe the unstated question was about fuel economy, and the identification with the less revolutions per minute for the greater fuel efficiency. I believe, the research will point to the tire that is shorter/more rotations per minute but creating less drag. (22.5 is more fuel efficient.) abridged

 

63360 inches in a mile 5280 ft. divided by circumference -diam. X 3.14 = circumference You can find rpm if you know final trans ratio-rear end ratio and tire diam. You can find tire size if you know rpm-trans ratio and rear end ratio. You can find trans ratio and rear end ratio using the same formula. Wasn't very smart in math but can find the unknown of mph-rpm-trans ratio-tire circumference and rear end ratio if I have the information of everyone except one (X) algerba