Speedo re-calc 6.7L

[CUMMINZ]

Got my new 19. 5x245s today. Went to local DC dealer to re-calc my speedo. We tried to just set the revs per minute but it had only three choices.



Tire size, gear ration & size of pinion or some kinda counter in differential.



245s were not an option.



Any ideas?

 

[gsbrockman]

Unfortunately, since the 2006 MY, tire revolutions per mile cannot be modified in the computer. I'd suggest a SMARTY or other programmer.



Greg

 

[salstrip]

tyre size

if you go to this web site Tire Size Calculator - tire & wheel plus sizing you can input your new tyre size and compare it to the options available for the change tyre size on the starscan(connected to your vehicle) there should be one fairly close . we use 325/50/20s down here in Australia and they have the same rolling diameter as the 285/70 17.

Regards Conn

 

[CUMMINZ]

We have tried that. Changing gear ration and or largest tire size does not make any difference in speedo. I setup my laptop with GPS in truck and used the speed displayed on it and nothing we have tried works. Dealer has call into DC for answer.



Cumminz

 

[MonteW]

Got my new 19. 5x245s today. Went to local DC dealer to re-calc my speedo. We tried to just set the revs per minute but it had only three choices.



Tire size, gear ration & size of pinion or some kinda counter in differential.



245s were not an option.



Any ideas?

Pick closest to the 245s, or do like I do with my 2007. 5/6. 7 engine. I just run a G. P. S. it is more accurate. My G. P. S. is usually 3 to 4 miles faster than the spedometer.

 

[CUMMINZ]

I spoke to my dealer last week. He contacted his DC person and they said there is NO way to correct speedo. When we set the tire size to different to various sizes it made no difference. I did connect my laptop to GPS while I was doing this testing. With the 245x19. 5s the speedo is 2. 5 mph slow.



CumminZ

 

[Newt]

Most factory tire size adjustments are only available for original factory tire sizes. A tuner will fix you up.

 

[MLodge]

I am testing the smarty s67 right now. I was able to switch my tires to 37's with no cel's. So, when it comes out, you should be able to adjust your speedometer then

 

[salstrip]

new smarty

Wow how is the new Smarty ?Oo.

Regards

Conn

 

[MLodge]

Wow how is the new Smarty ?Oo.

Regards

Conn

I like it so far. I have tried a couple different power levels. The torque on the high setting was awesome all through the rpm range. I think it will be a nice unit when it comes out.

 

[salstrip]

when will it be released

do you know a release date for the smarty?

Regards Conn

 

[MLodge]

I have no information on the release date. I am still sending all of my testing information in to my shop. ie... egt's, mileage, etc... .

 

[FullerM]

So are you guys saying that there is no fix for larger tires? I changed to 37/13. 50/20's they look *****in but the speedo says 50 but gps says 59. 7

 

[Bob Wagner]

The smarty will start shipping on the 14th . Tire size calibration to 44"



Thanks

 

[JohnBower]

FYI: Hypertech makes a Speedometer Calibrator for the 6. 7's. I don't know how much it costs but it also can remove CEL's.

 

[FullerM]

whats a cel?

 

[Bob Wagner]

whats a cel?

Check Engine Light