Switching 22.5's to 24.5's

http://www.roadranger.com/ecm/groups/public/@pub/@eaton/@roadranger/documents/content/ct_062746.swf

Big John,
This is off the Roadranger site. Lots of other good info there also... david

 

anyway after you change tires do EM reprogramming to get correct speedo reading

 

It will only change your MPH a little. We have 2 trucks on 24.5's with 3:70's and all do great. I have the instructions and chart to change your KW speedo if you want it. You just need to flip the switches on the back of the gauge.

 

I've never went larger, always smaller. Took one from 24.5's to LP22.5 Super Singles, really no issue there since it runs local pulling a hopper so speed wasn't an issue. And just took another from 24.5's to LP24.5, this one was the biggest change. It was geared perfectly 24.5's 3:36's and a 13spd, any speed below 65 you just ran 12th gear and 65+ you used 13th. But after the tire change 12th kept the RPM too high and the truck didn't have enough power to run 13th (always hauls permit loads up to 120k). It was right on the line and extremely annoying, in 12th at say 60mph it ran 1500rpm and 13th it was down to like 1250-1300. The truck is a C15 Acert so 1350 is the sweet spot. Ended up going with a stage 1 PDI tune and now power isn't an issue and it can just stay in high gear.

 

do you happen to have the instructions still i have an 03 t800 with c15 13 speed and 3.70s truck came out the factory with 11r22.5 but dealership switched out to 295/75/22.5 so speed is off by a couple i have to use the gps to make sure of my speed

 

I have the formula and chart in a file at work. I'll get it tomorrow and send it to you.

 

I changed my rear end from a ratio from 3.58 to 4.56 when converting a tractor to a rolloff truck. I am using regular 22.5 tires and i noticed that my speedometer is reading 60 mph when it should be reading 48mph per my gps. Would changing to 24.5 decrease my RPM and increase my speed reading ton the speedo.

 

low pro 24.5 is the same height as 11r 22.5 I took off my l.p. 22.5 & put on 11 r 22.5 which gave me a lil more top end speed. so m.p.g is better, but less pulling power on the hills. I cannot say which is better over all on m.p.g. cause I changed over 1 month after I bought my truck. some say less r.r. with low pro.. but they will also have a higher r.p.m. too. good luck.