I looking at getting some new tires, so I called the dealer to see how large I could go where they could calibrate the speedo. The guy told me they can't recalibrate it. I thought I have read where guys said that they had this done. Anyone out there have this done or had this response from their dealer? I can't stand these dealers sometimes, they just give you a no answer without even knowing the facts. Or maybe I don't know the facts.

 

285 is it.........

Bob

 

that is correct

 

I guess I'll have to find a dealer that knows how to recalibrate it then. That's what I thought, but then I read someone say if you know the revs per mile then they can calibrate it that way also. I just got back from the tire shop and got some 285 terra grapplers. We'll see how they do. Already got some snow in the mountains. I'll go try 'em out next weekend.

 

the 07's will not let you enter revs epr mile anymore.....

 

Why is that? Boy am I glad I saw this thread. When I get my new 6.7, one of the first mods I was going to do was 35's. That would not have been good to roll with an uncalibrated speedo....

 

I put 37" tires on mine and with my edge it will show me of how fast I am going but it is not correct on the truck speedo. One of my buddies thats a mechanic said something once about there is something to do with the abs system where you can adjust the speedo alittle bit but it did not give you alot of adjustment, if that helps anyone.

 

Just a what I noticed on my 08 traveling to Daytona Beach, I hooked up my GPS and it seems to read exactly what the speedo is. So I am under the assumtion that it has self calibrated itself, has anyone else came across this with there gps? I will be headed back in a couple of weeks so I will run it against the GPS and see if the speed and mileage matches again. I have the 285 terra grapplers from my 04.5 on there now.

flgc

 

I hate my speedo being off! The dealer tried twice to get it close but I'm still off about 4mph at 60.

I can't believe that Dodge didn't program the computer to be able to adjust the speedo, just plain stupid.

 

I put 285 Terra Grapplers on and my speedometer is off just a little over 1mph by the GPS.

 

There is a way to calibrate the speedo. You have to tell the truck it has different gears, and a different rear end size. You then have to adjust the tone ring size. All this is done with the Starscan. I know it sounds crazy, but we have got up to 37's bang on. The truck shifts way better as well because the tranny is somewhat dependant on the speed sensor for accurate information. Please do not lump all dealers in the same pot. Some of us just try harder than others.
NM

 

I also did what dslburner said... except i didnt mess with the tone ring size.. But i did get a Bully Dog Power Pup and when i use its tire size tool and set it as 33"s and have my gears messed with via the start scan, my speedo is dead on with my 35" Toyo MT's... I based this on driving and using a handheld GPS device... It says 79.8 MPH when i set my cruise at 80 MPH... So its right on

 

Is it just the 6.7 trucks that cannot be calibrated? I have an 07 but its a 5.9 so I am wondering if mine can still be calibrated based on tire revolutions..

 

Would you like to explain to me how I can get my speedo calibrated using this method? I will take your info to my local service dept.

 

I would explain it, but I am not a tech. If you go to your dealer and find the guy who is best with the starscan, they will figure it out. All 06-08 HD trucks are this way.

NM