[Piesen]

I'm now using the CS and have uploaded the canned Tow tune, and changed the tire size to truck specific 255/70 R17 and now the speedometer is off by 4-5 mph, before it was of by 2 mph or so this according to GPS.
If I remember correctly the cs said the tires were 275/65/R16 before I changed the parameters.
I'm not sure I quite understand, Can anyone explain

Also I can't seem to find the AVG MPG setting, only instant MPG any way to change that or is that the way it is.

The manual is very superficial with info.

Thanks

[shotgun]

The current CS/CTS does not support the AVG MPG.

Did you program the tire size BEFORE you flashed the level 2 (tow) tune?

[Piesen]

Yes I did
thanks

[shotgun]

The CTS does NOT account for squish when calculating the revs/mile. You have to do this manually.

Flash back to stock and try setting the tire size to 2404mm (this accounts for 3% squish on a 255/70 R17 tire). Also make sure the gear ratio is correct.

If this doesn't get you real close, double check your tire size on the tire.

If it's close but you want to get closer, decrease your tire size if the CS speed is higher than the GPS (and vice versa).

As an example, if you're off (high) by 2 MPH at 60, decrease the tire size to 2323mm (2404 x 58/60).

[shotgun]

Did you get a chance to confirm your CTS MPH vs. your GPS?

[Piesen]

I have, but not at 60 mph but at 45 the CS and Gps are Identical its just the In car speedometer thats off.
Wednesday I'll have to hit the freeway for awhile and will check at a higher speed
thanks man

[shotgun]

Originally Posted by Piesen

I have, but not at 60 mph but at 45 the CS and Gps are Identical its just the In car speedometer thats off.
Wednesday I'll have to hit the freeway for awhile and will check at a higher speed
thanks man

You're welcome!

You'll find the dash display will ALWAYS read 2-4% higher (2-3 MPH at 60+ MPH). If your GPS and CTS are identical, you're good!

[SportTractoF150]

Originally Posted by shotgun

The CTS does NOT account for squish when calculating the revs/mile. You have to do this manually.

Flash back to stock and try setting the tire size to 2404mm (this accounts for 3% squish on a 255/70 R17 tire). Also make sure the gear ratio is correct.

If this doesn't get you real close, double check your tire size on the tire.

If it's close but you want to get closer, decrease your tire size if the CS speed is higher than the GPS (and vice versa).

As an example, if you're off (high) by 2 MPH at 60, decrease the tire size to 2323mm (2404 x 58/60).

What would be the mm sizing be on a **** Cepek Radial Fun Country II in 35x12.5x20 inch size with the squish factored in? Also, I'm not sure but I do not think it is a true 35" tire, maybe 34.2". Does anyone know for sure?

Also, do you have to change the tire size before you change the Tune Level?? I did it after it changed it to Level 2.

[shotgun]

Originally Posted by SportTractoF150

What would be the mm sizing be on a **** Cepek Radial Fun Country II in 35x12.5x20 inch size with the squish factored in? Also, I'm not sure but I do not think it is a true 35" tire, maybe 34.2". Does anyone know for sure?

http://www.dickcepek.com/tires.php?item=RadialFCII

Also, do you have to change the tire size before you change the Tune Level?? I did it after it changed it to Level 2.

I responded on F150online, but you must change the tire size first and then flash the PCM.

[SportTractoF150]

Thank you very much for your response on both sites and thank you for that link.

So from that, it says the tire is overall 34.6 inches tall. That converts to 878.84 mm, and with 3% taken out for squish, it makes it 852.4748. So would I be correct in putting in 853 mm as the measurement? Did I do that right?